Full suspension mountain bikes are rather brilliant things, although they come with one significant downside. Their linkages pivot around bearings, which over time wear. If left unchecked, worn bearings will result in poor suspension performance and could even ruin your frame. Here, we'll go over how to identify worn pivot bearings and how to change them.
Disclaimer - Bearing replacement can be considered an advanced aspect of bike maintenance. If you’re not confident after reading this, book your bike in with your local mechanic, it’ll be cheaper than a ruined frame.
How to tell if your bearings are worn
Generally speaking, full pivot bearing replacements are best done on an annual basis. Not only does this act as some very important preventative maintenance but it’ll keep your bike running as sweet as the day you bought it.
However, bearing replacements are often something that’s done on an as-and-when basis, which is useful if you’re budget-conscious. Your bearings may even wear out before a full year’s up if you’re riding through muddy conditions often, for example.
As with any of your bike’s bearings, you’ll know when a pivot bearing is worn when it develops a bit of play. To quickly find out if there is any play, gently lift the rear end of your bike without letting the rear wheel come off of the floor. Everything should be solid and there shouldn’t be a loose feeling or any noticeable knocking with each pivot bolt torqued correctly, if there is, you’ve got a (or many) worn out bearing.
Note – This can also identify a worn shock bushing. To troubleshoot this, feel around the shock eyelets. Any knocking here indicates tired bushing.
You can also rock the frame and feel for movement in certain areas. This will tell you which exact bearings want changing and it's good practice to do this when buying a second hand bike.
A sure fire way of checking for worn bearings before play develops is to remove the shock and circulate the rear end. A rough, notchy feeling or any stiffness suggests that there’s a bearing that needs replacing. If something isn't smooth, it’s time to get some bearings ordered and reach for the wrenches.
It’s more than possible to take the frame apart and feel individual bearings for wear and play by rolling them with your finger to check if you only need to replace a few. Although, if one is gone, you might as well tackle the rest to save you from having to go back sooner than you need to.
How to find out which bearings you need
Before taking your frame apart, get hold of a full set of replacement bearings if you can. Manufacturers often offer full-bearing kits for their frames online or kits can be found from third-party suppliers. You can also contact the manufacturer directly and they should be able to help you out. If not, it’s time to grab the correct Allen keys and get diving deep into your frame. Here, I’ll take apart the frame only enough so I can read the markings on the bearing’s seal.
Every bearing has a code on its seal, 6902 LLU, for example. The ‘6’ in this instance is the type of bearing, the ‘9’ is the bearing series and the ‘02’ is the bore size. The letters afterwards describe the kind of seals that the bearing uses. In the case of ‘LLU’ it’s Endurobearings’ full contact, dual lip seal that’s designed for headsets and pivots.
When you’ve got all of the codes of the bearings, you just need to buy bearings that match the first four digits at least. While you can interchange bearings with different seal types, you cannot put a 6902 kind, into the race of a 6901, the numbers must match.
The tools you’ll need
This job can successfully be done with bodged tools such as a threaded rod with washers and nuts but because this is a task with very little room for error, I can only recommend using purpose built tools. They’ll make the job much easier. This is what you’ll need.
- Slide hammer or bearing puller tool
- Mallet and suitable object to hit (only when using bearing puller tool)
- Spanners compatible with your slide hammer or bearing puller tool
- Bearing press with correct sized drifts
- A rag (multiple rags are definitely handy)
- The Allen keys to match your frame bolts
- Good quality grease
- Thread locker
- Workshop stand
- A pair of gloves is also useful; things can get greasy
How it’s done
The principle of replacing bearings is to pull them out of their races and press fresh ones in, so this method will work similarly to what you'll do with hub bearings. It sounds easy and generally, it is but it’s best to approach the job with a cool head, a tonne of patience, and equipped with a cuppa.
1. Disassemble your frame
Of course, to get to your bearings, you’re going to need to take your frame apart. While doing so, be sure to lay any bolts, spacers, and seals out on a clean rag or bit of shop towel. This way, you’ll reduce the chances of losing vital frame parts.
Often, pivots are hidden behind your bike’s chainring, so you’ll need to remove your crank and for ease of access, it can be useful to remove your bottom bracket.
If you're only partially disassembling your frame to reach an individual bearing, use rags to keep any loose parts from harmfully knocking against each other.
2. Clean your bike
This is the best opportunity you’ll ever get to clean the areas of your bike that you’ll rarely be able to reach when your frame is in one piece. This goes for all of the bolts and spacers you’ve laid out too. It’s worth taking the extra bit of time to clean all of these parts as you won’t see them until the next time you replace your bearings.
3. Remove the frame bearings
Now, it’s time to get those bearings out of the frame. This is done by force, with a slide hammer or bearing puller tool. If you’re using a slide hammer, pick the right size extractor for the bearing and tighten it up using a pair of spanners. Then, assemble the rest of your slide hammer.
With the puller assembled, pull back on the slide hammer’s slider forcefully and the bearing will slowly coax out. It’s best to take care, and take your time while doing this, as some bearings are tougher to remove than others. This is because often when put together at the factory, not enough grease has been used or grease has simply washed away when riding and the bearing as rusted in place.
If you’re using a bearing puller tool, you insert and tighten as you would with a slide hammer, but you’ll need to knock the bearing out from the other side of the frame with a mallet and something long enough to reach the tool but sturdy enough to withstand being hit.
Note – There will be spacers inside of your frame between the bearings, make sure to give these a clean and keep them safe as you’ll need to replace them later.
4. Clean the races
Now the bearings are out of your frame, with a rag and a touch of degreaser clean the races out as best you can. Usually, there will be traces of old and gritty grease. Again, these are areas of the bike you shouldn’t be seeing for a long time but pressing fresh bearings into races with old grease could lead to creaking and no one likes that.
5. Press the new bearings in
With all of the races clean, it’s time to press the fresh bearings in but before you reach for the press, prepare those races by lining them with high-quality grease. This will make insertion easier but importantly, it should make removal next time a bit easier.
Next up, coat the fresh bearings with grease and assemble your press. It’s best to press each bearing in one by one so the non-bearing side of the press has something flat to sit against to help the bearing slide in straight. This is important as pressing a bearing in wonky could damage your frame.
On the other side of your press, you’ll need your bearing, of course, and the correct size press plate. Sometimes to provide clearance for the press’s handle, you’ll need to add a spacer or two.
Now, simply turn the press’s handle to push the bearing in. Do take your time and watch carefully. The bearing should press in fairly easily. If it takes a bit too much force, it’s likely the bearing isn’t going in straight. If you can, remove it and try again.
Before pressing bearings into the opposite side of the frame, make sure that you put the spacers that sit between the bearings inside of your frame back where they belong. You don’t want to have to remove bearings again because you’ve forgotten these.
Finally, wipe away any excess grease, though it is a good idea to leave a film over the bearing itself. This will add a touch of resistance against moisture.
6. Reassemble your frame
Now your frame is full of fresh bearings, you’ll need to reassemble it. This can be the trickiest part of the job so as with everything else, take your time or better still, find a friend to help.
You’ll need to put all of the spacers and seals back where they belong too and they can be quite hard to keep in place. A useful tip is to add a small blob of grease to the side that contact the bearing. This will stop the spacer from dropping off but it won’t stop it from moving around as you slide one frame component over another.
The best way to reassemble a frame is to work in reverse order and be sure to add a touch of thread locker to the pivot bolts. Once in one piece, torque up all of the bolts to the required specification and you're all set.
Again, if this isn’t something you’re confident with, please bite the bullet and give your bike to a trained mechanic.
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