Helmet Selection Variables and Aerodynamics

Tuesday, June 8th, 2010

A version of this article was originally
published in Triathlete Magazine

I’m interested in getting an aero helmet. How should a properly adjusted helmet fit and which helmet is the fastest?
Macy, Internet

Dear Macy,

Multiple wind tunnel studies indicate that aero helmets offer one of the highest ratios of aero benefit to dollar cost of any single piece of equipment currently available to a time trialist or triathlete. With estimated median aerodynamic drag benefits for most amateur riders ranging from 3-6% (8-13 watts), the potential benefits of an aero helmet are hard to ignore.

The only independent wind tunnel test of aero helmets that I am aware of (Blair, 2007) was performed under brand anonymity. However, the test concluded that while some models tested better in certain conditions than others, all of the aero helmets tested offered aerodynamic benefits at yaw angles of 0 to 15 degrees (the test did not go beyond 15 degrees) when compared to a standard road helmet. The summary also stated that, “the results show that there is no clear choice among aerodynamic helmets for all riding conditions…”. Like any piece of aero equipment, field or wind tunnel testing on the individual rider who will be using the helmet is the only way to discern subtle aerodynamic differences between models.

When it comes to aerodynamics in general, and aero helmets in particular, things are rarely as simple as wind tunnel numbers may make it appear. Aerodynamics is a “package deal” and your riding technique and form are of great importance. The best TT riders and triathlon cyclists tend to have exceptional riding technique and part of optimizing this technique is knowing that their riding position and equipment are working to the fullest potential. In the case of aero helmets, this means holding and maintaining the helmet in as stable and aero a position as possible. The more stable and consistent the head and upper body position, the more significant the likely aerodynamic benefit as the wind will maintain a more laminar (smooth) flow around the helmet and the rest of the rider and equipment. If you know that you often stretch your neck, turn your head to the side, or tuck your chin when riding, an aero helmet’s aerodynamic benefits could be significantly diminished.

Outside of aerodynamics, as with any helmet, comfort, weight and ventilation are significant variables too. The importance of comfort in a helmet is self-explanatory and an ill-fitting helmet will not protect you the way it was designed in the event of a crash. A properly sized helmet will fit comfortably snug, resting about 1” above your eyebrows and contacting the top of your head as well as the front and sides. Your helmet straps should be close to your head and relatively taut with the chin strap adjusted so that when you open your mouth, the strap pushes against the bottom of your chin, but does not limit your jaw. A well fit helmet will stay firmly in place when you shake your head and there should not be gapping between the helmet and your head. A good way to check shell size is to place the helmet on your head and pull it straight back and forth and side-to-side. A well fit helmet will not have space between the shell and your head and will not knock your head when you perform the maneuver above.

Helmet weight is important in much the same way that the weight of a running shoe is notable. While few of today’s helmets feel heavy on their own, you do need to support the weight of your head and helmet with your neck and, over a long ride, ounces can add up. Aero helmets are usually heavier than standard road helmets and while the lightest helmet is not always the best helmet, make sure that your helmet is light enough so that it does not become burdensome. Especially if you are a distance athlete, remember that you are likely going to be logging some significant miles and time on your bike. An aero helmet that is reasonable for a one hour ride might not be as functional for a six hour ride.

Ventilation is also a significant item to consider when buying a helmet. One of the more effective ways to lower drag is to minimize the number and size of wind disrupting vents. Make sure that your helmet is adequately ventilated for your use, as even the most powerful and aerodynamic engine will seize up if it overheats. Other design elements, like ear covers and eye shields, can further enhance the aerodynamics, but they can also reduce ventilation. For this reason, some popular aero helmet brands, like Louis Garneau, offer multiple models to match the needs of a variety of athletes. The LG Rocket and Super Leggera models offer full ear coverage and can be fit with an optional eye shield, making them great for time trialists and triathletes who are willing to trade a little ventilation for aerodynamics, while the Chrono model is cut higher for those athletes who want greater side ventilation in an aero shape. For the rider who wants ear covers or a shield on some rides and may not on others, the Rudy Project Syton proves that a modular design offers the benefit of flexibility, allowing the rider to add or subtract aero features as wanted. While ventilation and aerodynamics are sometimes (but not always) conflicting design aspects, you have to determine what is a reasonable balance for your body and riding. If you are doing 40Km time trials, the aero benefits of integrated ear coverage and eye shields are likely worth the extra heat, if you are doing an Ironman in the heat of Hawaii, they may not be.

With so many strong options from the aforementioned brands, as well as Giro, Spiuk, Lazer and others, there is an aero helmet that will fit and work well for just about any rider and event. Find an aero helmet that fits you well and practice your aero riding technique and you will find yourself riding faster without working any harder.

Ride hard and smart!

Ian

Posted in Ask Fit Werx Article Archive, Triathlon |

Why Do We Bike Slower In The Cold Weather?

Wednesday, May 5th, 2010

By Dean Phillips, Fit Werx

Have you ever noticed that your average bike speed is slower when it’s cold out? Look no further than any local 10-mile weekly time trial and some riders seem to be up to a minute slower on the coldest days compared to their PR times on warm mid summer days. The opposite tends to happen in running road races – hot temperatures always seem to result in slower run times. So why do cyclists go faster in these conditions?

Fortunately for cyclists, warm days provide two distinct benefits that runners don’t capitalize on: 1) Lower Air Density and 2) Lower Tire Rolling Resistance.

Lower Air Density

Air density is a measurement of how dense or thick the outdoor air is. Outdoor air temperature is inversely proportional to air density, so that means when the temperature gets warmer air density gets lower. Lower air density results in lower aerodynamic drag on a cyclist, so that cyclist will go faster for a given effort. How much faster? Let’s take an example of a cyclist that can ride a 10-mile bike loop in 28:30 or about 21mph on a day when the temperature is 80 deg F. This same cyclist rides this same 10-mile loop again on a day when the temperature is 50 deg F. The change in air density alone causes the time to increase to 29:00 and average speed drops to 20.7mph. Unfortunately for this colder weather rider, the losses don’t stop there, as increased tire rolling resistance will further reduce speeds.

Lower Tire Rolling Resistance

Tire rolling resistance measures how much energy it takes to roll your tires over the pavement. When a tire contacts the ground it deforms and then springs back to its original shape. Every time this happens energy is lost in the form of heat. A warmer tire has improved elasticity and will lose less energy during this contact with the pavement. Many riders have noticed that it’s easier to change a flat tire on a warm summer day when the tire seems to push back onto the rim with little effort compared to a cold day. While we know warmer tires have lower rolling resistance putting an exact value on that change is challenging. A rolling tire is continuously generating heat and while a portion of that heat is lost to the surrounding air, there is also a portion that heats up the tire itself. The faster the tire rolls the faster it heats up. A sunny day will keep the pavement hotter, which also impacts tire temperature. Different tire models will heat up at different rates as well. The exact change can vary, but you can expect to see tire rolling resistance increase approximately 6% for every 10 degree F reduction in outside temperature. Now let’s get back to our rider who’s already been reduced to 20.7mph because of increased air density on the colder day. Adjusting for the increased rolling resistance this rider will average less than 20.5mph and see the time increase to 29:18! This poor rider is going to go home thinking he/she needs to train more when the reality is the outdoor temperature alone caused the 50 second increase in time and 0.5mph reduction in average speed.

What About Overheating?

Will the warmer temperature reduce power output? If it gets hot enough and you ride long enough you will eventually see a decrease in power output on the bike from hot conditions. It’s unlikely that you’ll see a reduction in cycling power for events shorter than 20 minutes simply because they’re over before your body has a chance to overheat. Unlike running in the heat, cyclists still have a 20+ mph fan blowing over them that provides significant cooling even in hot temperatures. While your heart rate will likely approach record highs in bike events in the heat, when push comes to shove cyclists can still generate their normal power over these shorter durations. Even if there’s a small power reduction from your body overheating, it’s more than offset by the very fast conditions created by the warm temperatures so most riders won’t notice. In the end everybody rides the bike faster when it’s hot out.

The chart below summarizes the changes in speed and time to complete a 10-mile cycling event in these two temperature conditions. We’ll use examples of two different riders to show that these time reductions impact everybody similarly. Values for rider weight, power, aerodynamic drag coefficient (CdA), coefficient of rolling resistance (Crr), and air density are provided for comparison in each condition.

	Air Temp (deg F)	Power (watts)	Weight (lbs)	CdA	Crr	Air Density (kg/m^3)	Speed (mph)	Time	Result
Rider 1	80	200	150	0.30	0.0040	1.165	21.0	28:30
	50	200	150	0.30	0.0049	1.234	20.5	29:18	48 sec slower

Rider 2	80	300	200	0.35	0.0040	1.165	23.0	26:01
	50	300	200	0.35	0.0049	1.234	22.4	26:43	42 sec slower

The speed reductions don’t always end there either. In addition to the colder weather slowing you down, cyclists tend to bundle up in extra layers, booties, gloves, tights and jackets when it gets cold out. All these extra layers simply compound the already slower conditions by increasing aerodynamic drag further.

Keep all this in mind next time you blame those slower winter and early season speeds on lack of fitness!

DP

Dean Phillips is a co-owner of Fit Werx² in Peabody, MA. Dean frequently writes tech articles for Begginertriathlete.com and is humble enough that he would likely never tell you (so we’ll tell you for him) just how fast he is on a bike. Dean holds multiple TT course records in New England, having broken records previously held by some of America’s best pro cyclists and he set these while being a father of three your children and owning his own business. Dean knows speed and how to get the most out of his training time.

Posted in Ask Fit Werx Article Archive, Cycling, Training, Coaching & Rehab |

Does Your Power Decline When Riding Indoors?

Saturday, January 16th, 2010

Does Your Power Decline When Riding Indoors?

By Dean Phillips, Fit Werx

Many cyclists struggle to hold the same power output on a trainer that they maintain outside. Lack of motivation and scenery are often blamed, but the true answers are locked under the dust of your old physics textbooks from high school. I’ll save you the bad memories and explain…

The real reasons you struggle to hold power indoors are that there is less cooling effect and less flywheel effect indoors.

Less Cooling Effect

A cyclist cruising at 20mph outside experiences the equivalent of a big 20mph cooling fan continually blowing air over them. When you are riding a trainer, that massive 20mph headwind is gone. Without adequate cooling (just like any engine), your body temperature rises faster, your perceived effort goes up, and eventually your power output declines as you overheat. From a thermodynamics standpoint, this is an example of how forced convection from blowing air provides far more cooling than free convection in still air.

Like most cyclists riding indoors, I start my workouts with a warm-up that gradually builds power over time. My basement is around 55 degrees and I often found that once I reached about 200 watts of resistance I hop off the bike and turn the fan on. I wondered why this seemed to happen at around 200 watts and the answer became apparent when I revisited my HVAC design engineering days.

In HVAC design, when a building contained a room dedicated for heavy work, standards had us design that room at 55 degrees Fahrenheit with a cooling load designed to remove 2000 BTU/hr, or 586 watts, of waste heat per person. Studies show that a cyclist has a metabolic efficiency of roughly 25% and, based on this, we can calculate how much power goes to the pedals and how much is lost as heat by using the formula 0.25 = W / (Q+W), where W is pedaling watts and Q is waste heat to the surroundings. Plug in 586 watts for Q, and W = 195 pedaling watts and the answer is 586/195 ≈ 3. Cyclists release 3 watts of waste heat for every 1 watt that’s applied to the pedals. This means that a rider pedaling at 195 watts can usually do so in a 55 degree ambient temperature room without an overheating problem, but if they apply additional watts, they will likely start to overheat.

Doesn’t the rider’s size have something to do with this? Yes and no. Overheating has more to do with the absolute power you ride at, and less to do with the power relative to your Functional Threshold Power (FTP). In other words, regardless of your size and weight, hitting 195 watts in a 55 degree room is what matters. A larger stronger cyclist riding at 16 mph and producing 195 watts may start overheating during warm-up, while a smaller cyclist may be going 18mph at 160 watts and may never overheat in the 55 degree room as they never cross that magic 195 watt threshold.

Overheating occurs when riding at a high enough power level for a long enough time overtaxes the body’s cooling system. The most challenging indoor cycling workouts are those that stress both power and duration - the “double whammy” of overheating. Long intervals such as 2×20 or 4×10 minute intervals at FTP are common staples for cyclists and triathletes, but these are among the toughest to perform indoors without suffering miserably and/or experiencing power loss. A power loss compared to riding these intervals outdoors at the same wattage is inevitable without substantial cooling assistance.

Shorter higher intensity intervals are more reasonable to perform – such as 5 x 2 minute VO2 max intervals. While the intensity is higher and the effort is hard, there isn’t enough time for lack of cooling to negatively impact results the way it does in longer intervals. Longer lower intensity workouts are also less prone to power loss.

Based on this, some potential solutions to the increased heating demands of riding indoors are as follows:

Keep the room as cool as possible, preferably under 60 degrees. You likely will not win any points with your family or roommate(s) by opening the windows in the living room in January, so consider moving training to a cool basement. Remember, training must be tolerated by those around us first, and comfortable conditions come second. J
Use a large fan for cooling; the more air it blows across your body the better. You can increase the fan speed for higher intensity workouts.
When all else fails, restructure your indoor workouts into shorter higher intensity intervals and longer easier rides.

Flywheel Effect

When you stop pedaling on a flat road outside, you can coast up to a minute before coming to a complete stop, but when you stop pedaling on your indoor trainer, your rear wheel stops spinning in seconds. Why? Outside you have the momentum of the bike, rider, and spinning wheels; that’s a lot of momentum working in your favor. An indoor trainer replicates some of this momentum through the flywheel attached to the resistance unit - the larger the flywheel the longer it can hold its momentum. While a larger flywheel helps slow the deceleration of the rear wheel, it does not replicate the momentum you experience outdoors and thus you have to work harder to maintain momentum on a stationary trainer.

Because of the flywheel effect, the way you apply force throughout the pedal stroke also changes compared to riding outdoors. Outdoors, riding on flat terrain, we may think we’re pedaling in perfect circles at 90rpm from all those one-legged drills we did the prior winter, but the reality is the pedal force of the down stroke leg helps move the recovering leg through the back and top of the stroke and into position for the next down stroke. However, when you start to climb a hill, your pedaling becomes more similar to what happens on a trainer - if you ease off the pedals, you lose momentum quickly. Your cadence typically drops climbing hills or riding a trainer as smaller hip flexor muscles prefer to have more time to activate as they are lifting on the upstroke and pushing forward over the top of the pedal stroke. It’s quite common for a cyclist’s cadence to drop 20-30 rpm when they’re climbing a hill and riding at a lower cadence on an indoor trainer makes the effort feel more in line with that same perceived effort outside.

Try these solutions to give yourself more wheel speed and a larger “flywheel effect” riding indoors:

Only use enough press-on force on the roller drum to prevent the tire from slipping.
Use a trainer with a larger/heavier flywheel. Some trainers, like the Kinetic by Kurt, offer optional super heavy flywheel attachments.
Use a lower rolling resistance tire on the trainer. Many cyclists use big thick tires that wear a long time on the trainer, but those tires typically come with a rolling resistance penalty and rolling resistance is amplified on the trainer.
Take on the challenge of learning to ride rollers. The benefit of two wheels spinning instead of one improves road-like feel. If you can’t get the resistance you want on rollers, try higher resistance tires, smaller diameter roller drums, or - my favorite – letting air from the tires until you run out of gears right at the interval power you are targeting.

Once you’ve taken measures to improve flywheel effect riding indoors, the best solution is simply allowing your cadence to drop to a level that feels comfortable. Depending on the stationary trainer, I’ll let my cadence drop 5-15 rpm riding indoors. If you work with a coach, send them a link to this article and beg to ride at 85 rpm instead of 95 rpm for the workout you’ve been prescribed.

So there you have it. The keys to riding indoors at the same power level and perceived effort as you can ride at outside are: 1) Riding in a cool environment. 2) Find the largest fan possible. 3) Riding at a lower cadence to make up for the lesser flywheel effect.

Happy indoor training! J

DP

Dean Phillips is a co-owner of Fit Werx² in Peabody, MA. Dean frequently writes tech articles for Begginertriathlete.com and is humble enough that he would likely never tell you (so we’ll tell you for him) just how fast he is on a bike. Dean holds multiple TT course records in New England, having broken records previously held by some of America’s best pro cyclists and he set these while being a father of three children and owning his own business. Dean knows speed and how to get the most out of his training time.

Posted in Ask Fit Werx Article Archive, Cycling, Training, Coaching & Rehab |

Bearing Q&A

Wednesday, November 18th, 2009

A version of this article was originally
published in Triathlete Magazine

Since the August 2009 “Tech Support” on bearings was published, I’ve been asked some good follow up questions about choosing bearings and bearing ratings.

Question 1) “I’m not that technical. What is the biggest thing to focus on when choosing a replacement bearing?”

Look for quality and reputation over material and ratings. You get what you pay for and just being ceramic, like just being carbon fiber, does not always make something better. A high quality steel bearing made with top quality materials, grain structure and race polishing will perform better than a basic ceramic (even if the ceramic is “rated” higher) bearing. If a company like Ceramic Speed (the arguable inventors of ceramic bearings for bicycles) or Zipp (likely the earliest to offer ceramic options from the factory) is selling a high quality bearing for a certain price, you are not going to find that same quality bearing for significantly less money. Even if two bearings are rated the same on paper, if one bearing costs less, the lower priced manufacturer cut costs in the quality and refinement of the materials. These are things you can’t see or feel by looking at or spinning a bearing in your hand, but that are significant in how well a bearing works and lasts when it is actually being ridden under load.

Question 2) “Why do some companies list both an ABEC rating and a millions of an inch Grade rating?”

In the August article, I misstated that ABEC rates both ball and race tolerances and that millions of an inch Grade primarily applies to loose ball bearings only. “Radial Run Out” in regards to ABEC ratings is not the roundness of the balls; it is actually a measurement of the consistency of the roundness of the groove in the race that the balls roll. ABEC standards only apply to race symmetry and tolerances and do not consider the roundness of the balls. Grade, on the other hand, refers to ball roundness in either a loose or cartridge bearing and does not consider the race tolerances. Companies list both the ABEC (race tolerances) rating and Grade (ball roundness) because both ratings are important reflections of the tolerances in the bearing system as a whole.

Question 3) “Why are some steel bearings more expensive than some ceramic bearings of a higher Grade?”

Bearing Grade is not what matters most. Bearing Grade is universal across materials, so one Grade 10, regardless of whether the balls are ceramic, steel or silly putty, has the exact same tolerances/roundness as another Grade 10.

True bearing quality and performance comes down to the grain structure, polish and refinement of the materials used in the fabrication. You can have very round bearings and races, but if they do not offer appropriate material integrity and finish for each other, they will not work ideally together. For example, imagine you had two bearing systems with identical tolerances (Grade and ABEC ratings) and identical ceramic balls, however, one had races made of silly putty and the other steel. When they are unweighted and properly lubricated, both bearings might spin well in your hand, but what happens when you apply weight? The silly putty races deform, bind and grind to a halt immediately, while the steel still spins.

Now, let’s take this same concept of harder balls and softer races and apply it to common ceramic hybrid bearing construction. If ultra hard Grade 5 ceramic balls are placed in super hard, fine grained ABEC 5 steel races with proper lubrication, they will resist binding, pitting and deformation and will roll smooth and fast together for a long time. However, if you take these same Grade 5 ceramic balls and place them into ABEC 5 steel races that are not as fine grained and highly polished (softer), the substantially harder ceramic balls can wear the races much quicker. The race will pit and the softer race can even crack under impact loading (actual riding). The same thing can happen in full ceramic or full steel construction. In fact, some manufacturers will not even use a full ceramic cartridge bearing at this time as they have not found a ceramic cartridge where the races are strong enough to meet their standards.

In addition to making sure the balls and the races are polished and hard enough to wear well together, the quality and tolerances of the seal design, the volume of grease in the bearing and its formula, and the purity and cleanliness of the assembly process matters as well. Just like with carbon fiber construction, keep in mind that the easiest way to save money when building bearings is to spend less time refining the materials and assembly.

If you are choosing between a $25 Grade 10/ABEC 5 steel bearing offered by a manufacturer known for high quality engineering, materials and attention to detail or a $20 Grade 5/ABEC 5 ceramic hybrid from a supplier who sources their bearings from an unknown factory based in a country that may not recognize ABEC standards, the steel bearing will likely offer you higher performance. As stated previously, look at quality and reputation over material and ratings when choosing replacement bearings or considering an upgrade.

Question 4) “My bearings are worn out. Should I upgrade to ceramic bearings?”

On wheels, the answer is “Maybe”. High quality ceramic bearings in combination with tight tolerances hubs (DT, Zipp…) are a great combination. However, if you have high precision hubs and are wanting to keep bearing costs under $100 a cartridge, consider buying the very best quality steel cartridge bearing you can from a reputable manufacturer, as they will likely work better than a lower quality ceramic. If your wheels do not have high precision hubs, consider saving yourself some money and going with the best Grade and quality steel bearings you can. Less aligned hub shells actually require more bearing play to roll smoothly in the long-term and a high quality Grade 10-25 steel bearing will not only save money, but might work better and last longer than a tighter tolerance ceramic that may not be aligned in the hub shell as well as its tolerances require.

Partly because they use bigger bearings than hubs, just about all bottom brackets benefit from high grade steel or ceramic bearing upgrades. Shimano, FSA and SRAM cranks (amongst others) have a fair amount of seal and bearing friction that is noticeably reduced with a high quality bearing upgrade in ceramic (Ceramic Speed, FSA…) or steel (Chris King, Hawk Racing…). Because bottom brackets use bigger bearings than hubs, the tolerances and manufacturing precision don’t need to be as precise to gain the same performance. Note that no matter how high quality the bearings, if they are not mounted flush, they are going to be held back and could wear prematurely. Very few frames come from the factory with well faced bottom bracket shells, so make sure the shell is faced by a good technician before installation.

Ride hard and smart.

Ian

Posted in Ask Fit Werx Article Archive, New Bike Technology |

Bearing Grades and Quality

Wednesday, November 18th, 2009

A version of this article was originally
published in Triathlete Magazine

In the April 2009 issue of Triathlete, in the Tech Support column, there was an article that mentioned ceramic (hybrid) bearings and recommended a Grade 3 bearing or better. From the Internet, I found that some manufacturers say Grade 5 bearings are the best to get (for cycling applications), while others say Grade 3 is the best. If Grade 3 bearings are the best, does that mean that the Grade 5 Ceramic bearings used in my FSA bottom bracket and HED FR wheels are no better than a steel bearing? Thank you.

Jack, Louisiana

Dear Jack,

ABEC Grade 5 bearings are actually better than Grade 3 and Grade 3 was the minimum grade recommended in the article, so the bearings you have are some of the highest grade readily available in the cycling industry. The higher the ABEC grade of a bearing, the more symmetrical and tighter the tolerances of the rings (races) that hold the balls. Bearing ratings can be confusing and they only tell part of the story, thus some additional information may help.

Bearings in the cycling industry are rated by their ABEC grade and/or by their overall roundness in millions of an inch. Cartridge bearings are the most common type of bearings on bicycles and most companies usually rate by their ABEC grade over their millions of an inch grade. For this reason, I’ll discuss ABEC ratings first.

ABEC Rating: The “Annular Bearing Manufacturers Association” has a committee that sets standards for bearing precision called the “Annular Bearing Engineers Committee” - “ABEC”.

Cartridge bearings are the most common bearing type in the cycling industry. A “cartridge bearing” means that the balls, seals, grease and the internal and external races are all built into a single cartridge bearing unit that is usually press fit into the application. ABEC grading considers the precision of the rings (races) that the bearings roll on, but not the precision of the balls. The ABEC scale rates bearing precision on four levels: 1, 3, 5 and 7.

ABEC 1 is the lowest level of bearing that is considered “Precision”. ABEC 1 bearings are specified on three variables:

Bore - The Inside Diameter of the bearing - also measured as the size of the shaft (inner cone) that the bearings revolve around.
Radial Run Out - The roundness of the actual races.
Ring Width Variation - The consistency of the width between the inner and outer bearing rings. The more consistent the ring width around the entire bearing, the smoother the balls can roll between the rings and the higher the precision.

ABEC 3 bearings are rated on the same three dimensions as ABEC 1, although at tighter tolerances. For example, an ABEC 1 bearing will have .0003mm of Radial Run Out (roundness variation), while an ABEC 3 has only .0002mm of variation.

ABEC 5 bearings not only have tighter tolerances on the three core variables above, but they must also adhere to set standards on additional dimensional items within the bearing as established by ABEC. These additional tolerances provide greater precision and lower rolling resistance. The differences between a Grade 3 and 5 bearing for cycling are noticeable and many companies use Grade 5 for this reason. Grade 7 bearings tighten the tolerances further still.

It is important to note that the ABEC rating system only applies to the tolerances that ABEC sets as standards and does not consider some other important variables that can affect bearing performance and durability. Ball tolerances, materials, grain structure, grease, seals and manufacturing environment are examples of things that are not taken into account by the ABEC ratings.

Millions of an Inch Rating: You may also see bearings listed anywhere from Grade 2 to Grade 1000 in the cycling industry. These parameters simply refer to how round the balls are in millions of an inch. In this rating system, the lower the number the better the quality of the bearing and the harder and better finished the bearing. For example, a Grade 25 is round to 25/1,000,000″, while a Grade 1000 is round only to 1000/1,000,000″. For perspective, loose bearings found in a Shimano Dura Ace hub, would often be Grade 25.

So, what do you need to know when you are selecting bearings for cycling?

If you are looking at loose bearings graded between 2 and 1000, get the lowest number available for the application. The price difference is minimal between a Grade 25 and a Grade 300 or 1000 and the tighter tolerances and roundness of the bearings makes a notable difference in any rolling application (like hubs).

If you are looking at ABEC graded bearings, a Grade 1 bearing does not have very tight tolerances and performance will be limited. A Grade 3 is a significant step up from Grade 1, while a Grade 5 is where the performance “sweet spot” is located for cycling. This is why most ceramic and ceramic hybrid bearings for bicycles are Grade 5. Grade 7 bearings offer only a small gain in tolerances compared to Grade 5. The cost of a Grade 7 bearing can be up to ten times the cost of a Grade 5 bearing and would really only show further benefit in very high RPM mechanical applications (well beyond what can be achieved on a bicycle).

As mentioned above, because ABEC bearing grade only reflects precision of dimensions, you need to be careful that you still get what you want in other important aspects of bearing performance. For example, ABEC ratings don’t take materials or hardness into account and thus you can have an ABEC Grade 5 steel bearing, Grade 5 Ceramic or Grade 5 “hybrid” bearing.

Full ceramic bearings use ceramic balls and ceramic rings (races). Ceramic is significantly harder than steel, requires less lubrication and is lighter, so a top quality Ceramic bearing will offer less rolling resistance, greater durability and lower weight than a steel bearing of the same grade. Hybrid bearings are the most common type of “ceramic” bearings in the cycling industry. In a “Hybrid” bearing you will find ceramic balls rolling on steel races. So, look at the big picture and realize that if you want the full benefits of a Ceramic bearing system, you need to look beyond the grade and at the materials, the quality, and the fabrication of the bearing as well.

Hopefully this helps you select the right bearing for your needs and high quality Ceramic bearing technology is well worth considering if you are trying to maximize your performance and are upgrading a high precision component.

Ride hard and smart.

Ian

Thanks to Max Ralph at FSA for helping with this article.

Posted in Ask Fit Werx Article Archive, New Bike Technology |

Great Cycling Products You May Not Know About

Monday, April 27th, 2009

A version of this article was originally
published in Triathlete Magazine

Dear Tech Support,

Are there any products or services that most athletes could benefit from, but that many people don’t use simply because they are not familiar with them?

Fran, via email

Dear Fran,

This is a great question. Big and small, here are some things that are well worth knowing about. You can find (or order) these products and services through a good dealer.

Hutchinson Tubeless Road Tires: See Tech Support, Nov. ’08 for a more complete review, but Hutchinson’s Tubeless Road Tires are the smoothest riding, lowest rolling resistance and pinch flat resistant tires you can get. Specialized and Campagnolo, among others, have joined Shimano in producing tubeless specific wheels. An ultra light tubeless tire is available from Hutchinson too. www.hutchinsontires.com

Stan’s NoTubes kits and valves for Tubeless Road: Convert most any standard clincher road wheel to tubeless tire technology. www.notubes.com

Cushy’s Replacement Aerobar Arm Pads: CeeGees makes high density replacement arm pads for just about every aerobar known. Compared to most stock arm pads, the CeeGee’s “Cushy’s” pads last longer and support better. They also are one of the least expensive products you can get that will increase the vibration damping and comfort of your TT or Tri bike. www.cee-gees.com

Parlee Carbon Front Derailleur Clamp: Okay, this doesn’t improve your performance much, but it is super light, looks cool and mounts flush so you can put a bottle cage over the clamp without having to use spacers. Parlee makes nice road and tri bikes, including a well priced full carbon stock TT/tri frame, that are worth checking out too. www.parleecycles.com

Wide Ratio 10 and 11 speed Cassettes: A couple of years ago, SRAM started offering very functional and broad gearing combinations for the road that no one else was making. These cassettes apparently sold quite well, as Shimano’s new 7900 Dura Ace and Campagnolo’s new 11 speed cassettes offer broader gearing options than ever before. While they are not as smooth as Shimano on Shimano, SRAM cassettes work with Shimano shift levers too. IRD also makes wide range 10 speed Campagnolo and Shimano/SRAM compatible cassettes (like 12-32) for those looking to climb really big hills. www.interlocracing.com

Wheels Manufacturing Conversion Cassettes: Want to use a Shimano cassette body equipped wheel with your 10 speed Campagnolo shift levers? This is the solution. A wide range of effective gearing options and shifting that is as good (or better) than a Campagnolo cassette make a conversion cassette even more attractive. www.wheelsmfg.com

SMP and ISM Adamo Saddles: While there is not a saddle that works for everyone, these relief zone based saddles have helped a number of riders resolve soft tissue related saddle issues. www.ismseat.com and www.albabici.com

Ceramic (Hybrid) Bearings: If they didn’t work better, Formula 1 cars wouldn’t use them. Hubs, bottom brackets and derailleur pulleys can all benefit from an upgrade that minimizes rolling resistance, while maximizing durability. While you don’t need the most expensive ceramic bearings to see a nice improvement, be aware that cheap ceramic bearings aren’t going to offer you much over a high quality steel bearing. Get a Grade 3 bearing or better.

Hydrotail Carbon Rear Bottle Carrier: While most other bicycle components were using advanced designs and materials years ago, the rear mounted bottle carrier seemed to be in neutral – maintaining the same designs available in the 1990’s. Then, Beaker Concepts came out with the carbon Hydrotail. The Hydrotail was significantly lighter than previous options and led not only to the development of other carbon carriers, but also the redevelopment of better designed aluminum carriers as well. Today, both Hydrotail and X-Lab make carbon and alloy rear carriers that work better over a wider array of applications (including bike brand specific carriers), while being lighter and more functional than ever. www.beakerconcepts.com and www.xlab-usa.com

TUFO Tubular Tape: Fear tubulars no more. Two sided rim tape takes the mess out of tubular installation and cuts installation from a sometimes messy project that can span days to one that can be done in a matter of minutes. Note that TUFO can only guarantee this product when used on their tubular tires. www.tufonorthamerica.com/accessories.php

SwissStop Brake Pads: Does which brake pad you use matter? You better believe it. Especially if you use carbon rims (or mix carbon and alloy rims on the same bike), the SwissStop Yellow King pads offer dependable performance with wheels from a variety of manufacturers and under a wide range of conditions. www.swissstop.ch

Trigger Point Technologies Massage Kits: Almost every athlete has fought tight muscle adhesions or an injury and knows how much it can limit your performance and comfort. Developed by an athlete for athletes, the TPT massage tools and videos are great to use on their own, on the road, or as supplements to physical therapy or deep tissue massage work like Active Release Treatment. www.tptherapy.com

SRAM Rival, Force and Red Components: Ergonomic, mechanically simple, lightweight, well-priced, offering gearing ranges many riders have been asking for, and proven – SRAM went from nothing in the road world to major market player in under two years. Campagnolo and Shimano have been forced to take a close look at the designs of their fine components because of SRAM and the performance of bicycle componentry as a whole has benefited because of it. www.sram.com

Cycling Footbeds: Foot stability and support is key to maximizing power transfer and minimizing fatigue, yet the majority of riders still ride their cycling shoes without adequate support for their needs. A custom cycling footbed is the most comprehensive solution, while over-the-counter options like what SuperFeet, Specialized and Aline offer improvements over factory insoles for some riders.

“Fit First” Bike Buying: The vast majority of bikes bought today are “fit” after the bike has already been selected. “Bike First” selection is like designing the house after you have already built it - it puts the needs of the bike in front of the needs of the rider. There is a better way. “Fit First” bike selection puts the rider (you) first and foremost. By far the best way to find a new bike that will work optimally for you is to determine your optimal riding position first and then use this information to find the frame/bikes that are the best geometric matches for your needs. Search out and find a dealer/fitter that works this way. Don’t hesitate to travel to work with them as your biggest equipment purchase is too important to be left up to chance. www.masterbikefitters.com

Motion Capture Fitting Technology: Dartfish, Retül and other companies make technology that can provide more data with greater accuracy than ever before to bicycle fitting. However, realize that great technology doesn’t make a great bicycle fit. A hospital with all the best equipment is not much good without having the right doctors and the same is true with motion capture fitting systems. While bicycle fits and motion capture technology are advertised and offered just about everywhere now, there are a limited number of qualified providers offering true top level fittings. A well educated and experienced fitter in combination with modern technology can help you understand how to get the most out of bike and body in a matter of hours. Whether you are brand new to riding or have been riding for decades, a motion capture fit session with a top fitter will pay off for the rest of your riding career.

Ride hard and smart.

Ian

Posted in Ask Fit Werx Article Archive, New Bike Technology |

Helmet Selection Variables and Aerodynamics

Monday, April 27th, 2009

A version of this article was originally
published in Triathlete Magazine

I’m interested in getting an aero helmet. How should a properly adjusted helmet fit and which helmet is the fastest?
Macy, Internet

Dear Macy,

Multiple wind tunnel studies indicate that aero helmets offer one of the highest ratios of aero benefit to dollar cost of any single piece of equipment currently available to a time trialist or triathlete. With estimated median aerodynamic drag benefits for most amateur riders ranging from 3-6% (8-13 watts), the potential benefits of an aero helmet are hard to ignore.

The only independent wind tunnel test of aero helmets that I am aware of (Blair, 2007) was performed under brand anonymity. However, the test concluded that while some models tested better in certain conditions than others, all of the aero helmets tested offered aerodynamic benefits at yaw angles of 0 to 15 degrees (the test did not go beyond 15 degrees) when compared to a standard road helmet. The summary also stated that, “the results show that there is no clear choice among aerodynamic helmets for all riding conditions…”. Like any piece of aero equipment, field or wind tunnel testing on the individual rider who will be using the helmet is the only way to discern subtle aerodynamic differences between models.

When it comes to aerodynamics in general, and aero helmets in particular, things are rarely as simple as wind tunnel numbers may make it appear. Aerodynamics is a “package deal” and your riding technique and form are of great importance. The best TT riders and triathlon cyclists tend to have exceptional riding technique and part of optimizing this technique is knowing that their riding position and equipment are working to the fullest potential. In the case of aero helmets, this means holding and maintaining the helmet in as stable and aero a position as possible. The more stable and consistent the head and upper body position, the more significant the likely aerodynamic benefit as the wind will maintain a more laminar (smooth) flow around the helmet and the rest of the rider and equipment. If you know that you often stretch your neck, turn your head to the side, or tuck your chin when riding, an aero helmet’s aerodynamic benefits could be significantly diminished.

Outside of aerodynamics, as with any helmet, comfort, weight and ventilation are significant variables too. The importance of comfort in a helmet is self-explanatory and an ill-fitting helmet will not protect you the way it was designed in the event of a crash. A properly sized helmet will fit comfortably snug, resting about 1” above your eyebrows and contacting the top of your head as well as the front and sides. Your helmet straps should be close to your head and relatively taut with the chin strap adjusted so that when you open your mouth, the strap pushes against the bottom of your chin, but does not limit your jaw. A well fit helmet will stay firmly in place when you shake your head and there should not be gapping between the helmet and your head. A good way to check shell size is to place the helmet on your head and pull it straight back and forth and side-to-side. A well fit helmet will not have space between the shell and your head and will not knock your head when you perform the maneuver above.

Helmet weight is important in much the same way that the weight of a running shoe is notable. While few of today’s helmets feel heavy on their own, you do need to support the weight of your head and helmet with your neck and, over a long ride, ounces can add up. Aero helmets are usually heavier than standard road helmets and while the lightest helmet is not always the best helmet, make sure that your helmet is light enough so that it does not become burdensome. Especially if you are a distance athlete, remember that you are likely going to be logging some significant miles and time on your bike. An aero helmet that is reasonable for a one hour ride might not be as functional for a six hour ride.

Ventilation is also a significant item to consider when buying a helmet. One of the more effective ways to lower drag is to minimize the number and size of wind disrupting vents. Make sure that your helmet is adequately ventilated for your use, as even the most powerful and aerodynamic engine will seize up if it overheats. Other design elements, like ear covers and eye shields, can further enhance the aerodynamics, but they can also reduce ventilation. For this reason, some popular aero helmet brands, like Louis Garneau, offer multiple models to match the needs of a variety of athletes. The LG Rocket and Super Leggera models offer full ear coverage and can be fit with an optional eye shield, making them great for time trialists and triathletes who are willing to trade a little ventilation for aerodynamics, while the Chrono model is cut higher for those athletes who want greater side ventilation in an aero shape. For the rider who wants ear covers or a shield on some rides and may not on others, the Rudy Project Syton proves that a modular design offers the benefit of flexibility, allowing the rider to add or subtract aero features as wanted. While ventilation and aerodynamics are sometimes (but not always) conflicting design aspects, you have to determine what is a reasonable balance for your body and riding. If you are doing 40Km time trials, the aero benefits of integrated ear coverage and eye shields are likely worth the extra heat, if you are doing an Ironman in the heat of Hawaii, they may not be.

With so many strong options from the aforementioned brands, as well as Giro, Spiuk, Lazer and others, there is an aero helmet that will fit and work well for just about any rider and event. Find an aero helmet that fits you well and practice your aero riding technique and you will find yourself riding faster without working any harder.

Ride hard and smart!

Ian

Posted in Ask Fit Werx Article Archive, New Bike Technology |

Tubeless Road Tire Technology

Monday, April 27th, 2009

A version of this article was originally
published in Triathlete Magazine

Dear Tech Support,

The group I ride with has been debating whether a higher or a lower tire pressure minimizes rolling resistance – what’s the answer? Also, one of us has “gone tubeless” and is raving about the ride. I want to know is whether it’s hype or a real performance enhancer for us middle of the packers?

Chris F., via email

Dear Chris,

First, while the maximum listed pressure on some tubular tires can be around 200 psi., you will only increase rolling resistance, and the likelihood you will need to find a good chiropractor, by filling them to this level. While super high tire pressure may work well on a velvety smooth velodrome, even a freshly paved road does not even remotely approach this level of smoothness and thus tire pressure should be adjusted accordingly.

You should never exceed the maximum recommended pressure listed on a tire. Even if a tire’s maximum range is much higher, 100-130 psi is an optimal pressure for most performance road tires. Lighter riders (under 140 lbs) usually do better on the low end of this range and heavier riders (over 170 lbs) more towards the higher end.

How can rolling resistance decrease with moderate tire pressure compared to over-inflation? More than absolute pressure, tire rolling resistance is about consistency of contact patch between the tire and the road. When skipping and point loading over surface imperfections in the road occurs with an over-inflated tire, the tire casing deforms more and contact between the road and tire becomes less consistent. This, in turn, increases rolling resistance.

Second, Road Tubeless brings road bike tire technology into the modern era of tire design. Road Tubeless works on the same proven tubeless tire principles that performance motorcycle, car and mountain bike tires have used for years. A Road Tubeless system uses a specially configured carbon fiber/rubber bead, in combination with a matching rim shape, to create an air tight seal and eliminate the need for a tube. The end result is the best riding tire system I have had the pleasure of riding.

Some common questions and answers regarding Road Tubeless are:

“What are the direct benefits of Road Tubeless compared to traditional clincher and tubular tire designs?”

Significant enhancement in comfort and vibration damping. When you lower rolling resistance and tire pressure simultaneously, wheels ride better.
Excellent handling and traction characteristics. The casing on a tubeless tire provides excellent consistency of contact patch with the road and little deformation under load.
The elimination of pinch flats, even when riding only 80 psi on rough dirt with a road tire.
Low rolling resistance. When a friction layer (like a tube or tubular glue) is eliminated, lower rolling resistance can be a result.
Like a well glued tubular, Road Tubeless is very unlikely to roll off the rim in the event of a high speed puncture.
They hold air longer than average and require less reinflation.
Easy to repair. In the event of a flat, a standard clincher tube can be used in a Road Tubeless tire. Also, much like a car tire, a sliced tubeless tire can often be “plugged” and resealed again if damaged.

For short distances or long, Road Tubeless offers a number of potential benefits.

“Are Road Tubeless difficult to install?”

Road Tubeless tires fit on the rim looser than many clincher tires and frequently do not even require a tire lever. If you do use a tire lever, a tubeless compatible one is recommended so that you do not damage the tire bead. Anyone who is comfortable doing general maintenance on their bike should find the process reasonably straight-forward. Road Tubeless tires install best when liquid tire sealant is used in conjunction with a quick burst of air from a compressor or CO2 cartridge to catch and seal the bead of the tire to the rim firmly and quickly.

“What tires and wheels work with Road Tubeless and what do they cost?”

There is currently one tire – the Hutchinson Fusion 2 Tubeless – that offers the unique carbon/rubber tire bead matrix that can seal with a rim adequately to hold air. Luckily, the Fusion 2 Tubeless is a very well thought out and strong performing tire.

When it comes to wheels, things get a little more complicated. The only officially approved Road Tubeless wheel on the market is Shimano’s Dura Ace level 7850-SL. The rim on the 7850-SL has a bead and outer rim wall/valve that is designed to directly match up with the Fusion 2 Tubeless tire ideally.

This being said, companies like Stan’s No Tubes have researched using Hutchinson Fusion 2 Tubeless tires with a number of rim combinations and concluded that most any standard clincher rim can be reliably adapted to Road Tubeless with one of their rim sealing kits. Wheels with sealed outer rim walls, like Mavic’s venerable Ksyrium and R-SYS, do not even require using special rim tape to convert; a special valve and some sealant is all that is needed. A step-by-step instructional video on Road Tubeless installation and conversion can be found at www.notubes.com/movie_road.php.

Tubeless conversion kits run $30-$70, depending on the wheel. Hutchinson Fusion 2 Tubeless tires are under $70 each, similar to a high quality clincher and ultra light tube.

“Aren’t Road Tubeless tires heavy?”

No. While not the absolute lightest tire design, a Hutchinson Fusion 2 Tubeless is a competitively weighted tire at 290 grams (only about 20 grams more than a lightweight clincher and ultra light tube). With time, tubeless may even become lighter as the Fusion 2 Tubeless tire is the first generation of tubeless design while clincher and tubular tires are decades into their evolution.

“If the tubeless concept has been around for a while and works so well, why isn’t everyone using Road Tubeless?”

Some big tire companies refusing to participate and perception versus reality.

A number of tire companies originally competed to create the Road Tubeless tire standard. When Hutchinson’s design won, many other companies decided that instead of adopting the standard, they would simply not produce anything. This would increase the likelihood that the Road Tubeless concept would not gain much consumer momentum and would thus gather dust until Hutchinson’s patent expired.

Also, Road Tubeless tires, with their exceptionally smooth ride, will make some riders automatically assume that a firmer feeling clincher or tubular is faster. As long as “Feels faster” wins out over “Is faster”, many riders will shy away from new technology and many manufacturers will continue down the road they always have ridden.

Road Tubeless is well worth consideration by any cyclist or triathlete who is looking for an improvement over high performance clincher tires. Regardless of how short or how long your rides or events, Road Tubeless is affordable technology that works.

Ride hard and smart.

Ian

Posted in Ask Fit Werx Article Archive, New Bike Technology |

Wind Tunnel Testing, Virtual Wind Tunnel & Weight vs. Aero.

Monday, April 27th, 2009

Aerodynamics 101

You’ve got questions, we’ve got answers…

Howdy Tech Support from the great state of Texas. It seems like more and more products are being wind tunnel tested, yet multiple companies often claim that their product is the most aero. They can’t all be right in their claims. What gives?

Lincoln, TX

Dear Lincoln,

You have hit upon one of the great mysteries of the cycling world – how can so many things be the best? While wind tunnel testing has helped excel product development and improve performance, it has also often led to a significant amount of confusion as the test results can vary significantly in both concrete terms, as well as through interpretation.

In some ways, all the companies can be “right” in their claims. Under certain conditions they did likely achieve the results and it was likely the “best in test”. However, “best in test” may not mean much to your performance if the results do not translate well to the real world and your individual circumstances. Trying to boil aerodynamics and its relationship to performance down to this simple a level attempts to overly simplify a complicated subject that humans are still far from mastering.

From the yaw angle (angle that the wind hits the object), to the fixtures that hold the bike, and the wind speed used in the test, there is not a standardized test protocol for aerodynamic testing in the industry. Every test is thus its own entity and the results depend directly on the protocols used. Also, unless you are the test subject, none of the tests take the biggest aerodynamic variable into account – you. Each rider is shaped uniquely and has their own posture and technique when riding. For this reason, the helmet, frame, handlebar or other component that tests best under the test subject may or may not be the one that would work best for you.

Wind tunnel data, and continued development of aerodynamic computer modeling, will continue to provide useful information that helps with product development and helping make cyclists faster. However, it is important to realize that aerodynamics is a very personal and individualized concept; what works ideally for one rider or in a specified condition may not translate to working ideally for you. Do not choose your riding equipment based on wind tunnel data alone. Instead, consider the big picture and make sure the products you choose helps you stay as aerodynamic as possible without compromising power and comfort in the process.

IB

————————————————————————————————————

While I would very much like to go to a wind tunnel, I just can’t spend the dollars. Is there any way to accurately test aerodynamics without a wind tunnel?

Tom C., via e-mail

The short answer is “Yes.”

Researchers at the University of Utah, headed by Jim Martin, PhD, developed and scientifically verified an aerodynamics testing formula that consistently and accurately predicts aerodynamic drag. The results from these protocols are arguably even more valuable than the data a wind tunnel provides, as the results are in real world conditions. While it does takes some initial study of the procedure and equipment, the procedures are not difficult, are repeatable and scalable test to test, and provide very functional data. www.sportsci.org/2006/jcm.pdf is a link to a complete list of required items and instructions on the protocols to use and www.sportsci.org/2006/CdA_calculator.xls is a link to the associated spreadsheet for data recording and calculations. You need a power meter to complete the tests.

While you can do these tests on your own, it is easier to do it as a group and to test multiple people at once. In addition to the peer reviewed scientific proof provided by the Utah development team, we have anecdotal evidence that the formula works as well. Dean Phillips, one of our lead bike fitters, has used this formula to personally test a wide variety of equipment and riding positions for himself. Even though his training hours are down from three years ago, he has dropped almost three minutes of time off his 40K and broken many regional TT times, some that were set by pro riders over a decade ago, using the data he has gathered.

IB

————————————————————————————————————

How much does shaving weight on the bike really matter? As a follow up, what about becoming more aero? Are there any averages that can be used?

Trish, NY

The weight versus aerodynamics question is likely as old as the first bicycle race. Based on the work that provided the formula referenced above (Martin et al.), there is some excellent data on just how much different variables matter and what they will get you.

Some interesting statistics based on an average TT course and rider:

Reducing Weight: A 2% reduction in total vehicle weight (bike and rider) results in about 6 seconds of time savings over a flat 40K. If you and your bike weigh 180lbs together, this means you would need to take a huge 3.6lbs of weight off your bike to see this benefit. Most riders would have an easier time taking this amount of weight off their body. Interestingly, if you reduce weight by 2%, but also reduce power by 2% simultaneously, you will go about 13 seconds slower. So, no matter how light you can run your body, don’t lose power in the process or you will go slower.

Reducing Drag: A 2% reduction in overall drag results in about 12 fewer seconds to cover the same 40K. If you are willing to work at it, many riders could see 10-20% improvements in drag, which means a couple minutes.

What does this mean? It means for a fit athlete, you want a reasonably light bike, but realize that gram counting rarely pays off and that continuing to work on maximizing the potential of your maintainable aero position and equipment is where you will see the biggest speed gains.

Ride hard and smart.

Ian

Ian Buchanan is co-owner of Fit Werx. Fit Werx has locations in Waitsfield, VT and Peabody, MA and offers cycling and triathlon products, specialty bicycle fitting and analysis services, consultation, and technology research. Fit Werx can be reached in VT at (802)496-7570, in MA at (978)532-7348 or through the Web at www.fitwerx.com.

Posted in Ask Fit Werx Article Archive |

Power Meter Overview

Wednesday, September 17th, 2008

My coach wants me to start using a power meter when riding so that we can track my progress in the coming season in hopes that I can race more consistently. The two main options that I have found are PowerTap and SRM. There looks to be a pretty big price difference between these two. What are the big differences and what really matters? Thanks.

Jason , PA

Dear Jason,

Power training is becoming to the new millennium what heart rate training was in the 1990’s – the most effective way known to train. By combining heart rate and cadence data with power and performance data, athletes can learn a lot about technique and how their body performs. When done properly, power training not can not only help to make you a stronger rider, but it can also help make you a smarter rider.

There are a few popular options to record power and they each have potential benefits and limitations. While I’m only going to address units that were designed to specifically address power and that are accurate within +/- 5%, it is worth noting that companies like CicloSport offer price based cycling computers that provide estimated power output and Polar offers a basic power system that can be used with some of their heart rate monitors.

How Does a Power Meter Work? Most power meters use calibrated strain gauges to detect power output. Strain gauges are usually small metallic or wire grids whose electrical resistance varies proportionate to the amount of resistance (strain) put against them. The number of strain gauges in combination with the materials, construction and alignment used, determines how accurately a device reads.

What are the important things to consider?

Location of Unit - Strain gauges require a surface where there is pressure (strain) to gather data. On the drivetrain, there are three primary places that are used: the hub, the bottom bracket or the crank itself. Each of the three most popular power meters use a different location.

PowerTap places the strain gauges inside the hub body of the wheel. The primary benefit to this is that you can use any crank you want and, with an inexpensive additional receiver unit, a PowerTap wheel and computer head can be switched between multiple bikes. The potential limitation is that you need to use a rear wheel built around a PowerTap hub and each additional wheel you want power information from needs to be built around a PowerTap hub (starting at $420 for the hub only).

Ergomo uses a bottom bracket design. The benefits of this design is that you can use any rear wheel you want and the power reading is taken from the bottom bracket, which is close to the power source (the rider’s feet). The potential downside is that it is not easy to swap between bikes (you need to remove the bottom bracket) and while the new 2006 design is scheduled to be available in square taper, Octalink and ISIS crank compatible versions, it will not be compatible with the most recent generation of external bearing cranks (FSA Mega-Exo, Shimano Hollowtech II, etc…).

SRM is a crank mounted design. The primary benefits are that the power reading is taken directly off the crank (where the power is being produced), you can use any rear wheel you want, and switching between multiple bikes just requires an extra sensor kit and the ability to swap the crank to the other bike (under 5 minutes). The potential downsides are that some frame designs with uniquely shaped chainstays can require some creative mounting of the sensor and you need to use a crank with an integrated SRM unit in it. This being said, SRM offers a wide selection of cranks, including Octalink and square taper compatible designs as well as two of the latest and best external bearing designs on the market (Shimano’s Dura Ace and FSA’s Carbon Mega-Exo with standard or compact gearing).

Accuracy - All three brands claim accuracy that is within the needs of any athlete. PowerTap +/- 1.5% on their units, Ergomo +/- 2% and SRM +/- 5% to +/- 0.5% (depending upon unit). While there are some other differences in construction, in general, the higher the degree of accuracy a unit has, the more strain gauges it uses to read the output.

On Board Display - Each power meter computer head offers different features in regards to the data it displays and collects. All units include a full functioned cycling computer with cadence, while advanced functions like altimeters are also included with some units. Visit each company’s web site for specifics:

www.srm.de

www.ergomo.net

www.cycleops.com (PowerTap)

Dependability and Service - The units improve yearly in this regard. PowerTap had some moisture sealing issues on some earlier units, but anything available now uses an improved design to address this. While PowerTap has had some delivery delays historically, they have always stood behind the product. SRM started working with power meters in 1986 and their units are known to be dependable. SRM also has a U.S. based Service Center which turns units around efficiently and quickly if they need factory service. Ergomo recently changed distributors in the U.S. to Gita Sporting Goods and this change should help them handle any issues efficiently.

Weight - All power meters are going to add a little weight to your bike, but the information they offer more than makes up for the minor weight gain. Over a standard full Dura Ace equipped component group, Ergomo or SRM will add approximately 300g and PowerTap will add from 240g-400g, depending upon model.

Software - While all of the power meters come with software that allows you to download data into your computer, many of our clients prefer aftermarket software like Cycling Peaks (www.cyclingpeakssoftware.com). Ergomo includes a Cycling Peaks software package.

Price - If you just need to use your system with one rear wheel, PowerTap offers the least expensive options with the standard system starting around $800 and the lighter PowerTap SL systems starting at $1300. However, if you plan on using the system with more than one wheel, you need to add in the price of any additional wheels ($1500+ for a Zipp rim version). The latest Ergomo hub system is $1600 and SRM units all include a crank and range from $2100 up to $5200 for the extremely accurate (+/- 0.5%) Science version.

Power meters have gone from “high tech” concepts available only to the top pro athletes to readily available training equipment applicable to any serious athlete. All three designs offer functional and reliable power data so it comes down to where you want the data to be gathered (hub, bottom bracket or crank), how many bikes and wheels you want to use the power meter with, and what other components you want to use in conjunction.

Train hard and train smart!

Ian

Want more information on PowerMeters or want to order one of the systems discussed above? Contact us toll free at 866-833-4FIT or e-mail info@fitwerx.com.

Posted in Ask Fit Werx Article Archive |

Archive for the ‘Ask Fit Werx Article Archive’ Category

Lower Air Density

Lower Tire Rolling Resistance

What About Overheating?