are an integral part of the modern mountain bike. From headsets to hubs, bottom brackets to suspension pivots, cartridge bearings can be found on nearly every component whose purpose includes some type of rotation. We often take for granted the stresses and harsh conditions mountain bike bearings endure, rarely thinking about them until they make noise or develop play, typically after countless hours of abuse. To find out more, we spoke with Matt Harvey, one of the owners of Enduro Bearings, an industry leading company that offers an extensive line of bearings specifically designed for bicycle applications.
What are cartridge bearings?
In the bicycle industry, cartridge bearings refer to a bearing assembly that can be entirely removed What is the ABEC scale? For bicycles, what are the advantages of using higher rated bearings?
and replaced into the component such as a hub or bottom bracket. Traditionally, each bearing
assembly in a hub would consist of four separate components; a cup, a cone, a retainer and balls. Each
of these components (with the balls being held by the retainer) would be assembled as individual parts and
then adjusted with nuts and threaded axles on a hub or spindle assembly. Cartridge bearings replace
this four component assembly with one complete unit that is sealed with rubber seals. A radial
cartridge bearing consists of an inner and outer race, a retainer holding the balls and then two seals to
keep the grease in and the elements out. There is no adjustment feature for these bearings as they
are made with internal clearance or play. They are typically mounted by pressing them into a bore,
such as both sides of a hub flange, and then a slip fit axle is run through with stops behind the inner
race of each bearing. Nuts or top caps lock the bearings and axle into place. Again, there is some
internal play when they are tightened down. When the bearings wear out or they get rough or
contaminated, they can be removed entirely for servicing or replacement.
The ABEC scale and ratings refers to a number of tests and tolerances for radial ball bearings including What do the numbers on a bearing mean? For instance, 6802RS.
measuring their individual components, assembled components, and tests such as high speed
noise testing. Basically, these ratings refer to roundness tolerance of the inner and outer races,
trueness of the raceways, and radial and axial runout of the races. While the ABEC scale traditionally
has been used to pick out the best bearings for high speed applications, this does not directly apply to
bicycle bearings, which are considered a low speed application. But, the scale does give an idea of the
general level of precision and quality of the bearing. There are some other features which are more
important for bicycle application such as ball groove depth, ball complement (diameter and quantity
of balls) surface finish of the raceways, type and quantity of grease, design of seals, etc..., which
are not factored into the ABEC rating. Most high ABEC tolerances require the bearings be mounted
into high tolerance, ground surfaces with highly accurate spindles and bores to take advantage of the
precision level and trueness, which most bicycle components do not have, as they are machined parts.
In general, an ABEC 5 bearing is much more precise and accurate than the part it is being installed into.
Higher ABEC level rated bearings are higher precision and have tighter tolerances.
The numbers on a bearing refer to the series, dimension, and then the type of bearing. For instance, How water resistant are cartridge bearings? Will washing your bike with a hose force all the grease out?
6802 2RS refers to a bearing which is 15x24x5 mm with 2 rubber seals. "6800" is the series beginning
with a 10 mm bore. The increments go 10 (6800), 12 (6801), 15 (6802), 17 (6803), 20 (6804) and then
5 mm bore dimensions from there. A 6804 has a 20 mm bore, a 6805 has a 25 mm bore (5 x 5 mm = 25 mm),
etc. The 6800 series is called Extra Thin Line Bearings and 6900 would be Thin Line Bearings (larger section,
heavier duty bearing. A 6902 2RS would also have a 15 mm bore, but with a bigger ball, and has a 28 mm OD.
Finally, 2 RS literally means: Two (2) Rubber Seals. You may also find bearings with a number like 61802.
Here at Enduro that is how we designate our ABEC-5 line of bearings but dimensionally the 6802 is the same
as the 61802.
It depends on the grease and the seals that are used. "2RS" means Two Rubber Seals, but there are Why does play develop when a bearing is worn out? Are the balls themselves worn down?
many types. The usual 2RS seal is a single lip which runs dynamically on the outer part of the inner race,
the outer lip is static, and fits into a groove of the outer race. Enduro makes an LLB or LLU type, which is a
double lip seal that rides in a machined groove on the inner race. This, along with a water resistant or
marine grease will make it much more difficult for the grease to wash out of the bearing even when pressure
washing. That said, bearings ridden for long amounts of time in the rain or pressure washed again and
again will eventually need to be serviced depending on how often this occurs. Water will creep into any
sealed system given enough time in a wet environment. Using heavy degreasers and soaps will
also cause the grease to break down quicker, so be careful about what you spray on your bearings.
Here are the 4 variations of seal design that Enduro offers, LLU being the most effective at keeping water
out and contaminating the bearing:
Most times, it is the bearing raceways that are worn out when play develops. While the balls can wear What are angular contact bearings? What are the advantages of this design?
too, they are generally harder than the raceways and will wear the races out first. This is especially true for
ceramic balls, which are seven times harder than the raceways. This can be avoided by maintaining a proper
amount of grease in the bearing.
Angular Contact cartridge bearings (A/C) more closely resemble the traditional cup and cone bearings What are the benefits of ceramic bearings? It seems like when they first came out they garnered a lot of press, but now you don't hear as much about them. Any thoughts as to why this may be?
referred to back in point #1. While they can be made as cartridge bearings, until recently they could
not be removed and replaced as cartridge bearings because they would come apart into three pieces when
removed. This made servicing difficult, and if installed backwards, potentially disastrous. Enduro's newly
patented A/C bearings eliminate these problems with a unique design in which they can be removed and
replaced as other cartridge bearings without coming apart. A/C bearings do require a preload system being
either a threaded axle with no inner axle stops, or a spring or wave washer system with no inner axle stops.
With an angular contact hub or axle system designed to use these bearings, they can be adjusted to remove
wheel play. As play develops, they can be readjusted to remove it. While the same can be done with radial
bearings, these will wear out prematurely as the ball is rolling on a thin part of the race. A/C bearings are
designed internally to have the ball located at a 15º angle when preloaded. Because all of the balls are always
loaded on the races, there is always even load distribution.This is not true on a radial bearing with internal
clearance, where some of the balls are carrying all of the weight as the wheel spins. In this way, A/C bearings
will last longer.
Ceramic Hybrid bearings (steel races with ceramic balls) are still very popular and are here to stay. When www.endurobearings.com
they were first discovered by the bicycle industry, there was a lot of press because they were new. Suddenly,
many companies were offering ceramic hybrids, but like anything, there were some very good ones, and some
very bad ones. There was also a lot of misguided press claiming they would last forever. While they can last as
long as standard steel bearings, in general, good ones will last the same amount of time as an all steel bearing.
However, recently Enduro introduced XD-15 nitrogen steel races, and these will last much longer than steel
bearings with ceramic balls. This steel alloy holds up to the hardness and non yielding ceramic balls, even
without lubrication and exposure to any kind of elements. The Enduro XD-15 bearings will run just as smoothly
a year or two later as the day they were installed, even without service.