Lost your Bearings?
Everyone knows what bearings are, they're little devices that help things turn. They hide inside your wheel hubs, inside your pedals and even inside your suspension pivots. But like most little hidden components, they can cost you a lot of money. This guide will help you select the right bearings to keep things moving smoothly and hopefully for a long time.
The first thing you'll notice with bearings are the two main types. Loose balls held in by seperate cups and cones and cartridge bearings which are replaced as a unit.
Loose Balls with Cups & Cones
Almost everyone who's spun a spanner will know what these are. Your typical bicycle hub or pedal for the last 100 years or so has used them. They're simple, easily servicable (clean, regrease, replace balls if needed), adjustable, lightweight and are responsble for cumulative lifetimes spent searching for the ball-bearing that bounced across the floor while you weren't looking. Find a bikeshop with a hole in the workshop floor, look through it and you're guaranteed to spy a collection of long lost ball bearings.
Cartridge Bearings
These are the ones that everyone associates with skateboards and roller skates. A self contained bearing with hardened steel races inside and out with the balls trapped within. They come in a huge range of grades, types and sizes depending on the application. They're usually not servicable, while it's possible to carefully remove the seals and relubricate them, they're usually headed to the scrap steel bin (for recycling) when they wear out or sieze up. The great advantage of cartridge bearings is they are completely self-contained. A new bearing gives you new races (inner and outer), new balls, fresh clean lubricant and new seals.
Bearing Codes
Unless you're looking at something oddball (like a santacruz suspension pivot bearing) cartridge bearings all look much the same from the outside. An inner and outer race of shiney ground steel and some rubber or metal seals covering the space in-between and hiding the balls from view. On the seal or shield is usually a code explaining the bearing type. Here's how to decipher them.
Our example bearing has 608LLB moulded into the seal.
The code 608 indicates the bearing size, read through a bearing size chart and you can pick the dimensions.The correct name for the product we're looking for are "Deep Groove Single Row Ball Bearings"
Here is SKF's online product table:
Scroll through to page 4 and you'll see the size listed. 8mm ID, 22mm OD and 7mm wide. You'll also see a total of 8 different suffix's following the different 608 bearings. These suffix's indicate the seals and the bearing grade.
Seal Codes
- No suffix = no seals, the balls are exposed and suitable for running in an oil bath (say inside a gearbox).
- RS = rubber seals. 2RS = rubber seals both sides.
- Z = steel shields (non contact), 2Z or ZZ is shields both sides
- LLU/LLB are light contact rubber seals for less friction.
- RSH, RSL, RSR etc are all different types of rubber seal.
For a bicycle application, rubber seals are almost always the best choice.
Internal Clearance (c1, c3 etc)
We can normally avoid this section for bicycle applications. More internal clearance is necessary for parts with a really tight bearing fit (not your average bike hub) or running with high speeds or temperatures (again not your average bike hub). If you want to read more on C3/C4/C5 grades, have a look here:
aBEC & MAX grades
ABEC is a code the skateboarders have long been familiar with. An ABEC code indicates the grade the bearing is made too. Higher numbers indicate finer manufacturing tolerances and usually higher cost. ABEC1 is the lowest grade, ABEC9 is the highest.
Note that ABEC is an american standard that isn't adopted worldwide. The ISO 492 standard works in the opposite direction, ISO Grade 6x is the lowest, grade 2 is similar to ABEC9.
Where a normal bearing contains bearings with space between them and a cage to hold them apart, a MAX bearing is completely packed full of balls. MAX bearings are intended for applications where they see back and forth movement rather than continuous rotation. In these applications (like suspension pivots) they last much longer than a conventional caged bearing. But in applications like hubs or bottom-brackets which see continuous rotation they aren't a good choice. The lack of a cage results in the bearings rubbing on each other causing premature wear and failure. Raceface's X-type BB is a good example of a MAX bearing being specced in the wrong place, I have replaced a lot of these.
If you have any questions, please drop me a line, email is in the website below.
Cheers
Dougal
