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

Originally published in Triathlete Magazine November 2009/Copyright © 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:

1. Bore – The Inside Diameter of the bearing – also measured as the size of the shaft (inner cone) that the bearings revolve around.
2. Radial Run Out – The roundness of the actual races.
3. 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.

Originally published August 2009/ Copyright © 2009