Here is guide to change the bearings from a Sram GXP bottom bracket.
Integrated bottom brackets never last long. This is what we see generally after one or two years of use. . Cracking bearings, irreparable play… The Gaea that I have presented there a bit more than a year did no exception to the rule. The bottom bracket, despite being quite fluid, presents an important play. After dissassembly, it turned out that the play was caused by the right bearing, the left one being in good shape.
So what choice do we have to face this problem ? Buy the same 20€ bottom bracket that will last a year ? Upgrade to a Hope or Chris King, knowing that for the price of one, we buy 5 low ends ? Last solution : change the bearings only. In my case, for the price of one guenuine bottom bracket, I mount ABEC 3 bearings from Enduro Bearings (found at Purebike), which are quite high end compared to those found in common bottom brackets. Of course we will have to wait at least a year to see if this choice is relevant, but I already have a positive experience with this bearings that equipped the Powerway hubs of the Gaea MTB, and are close to new (still well greased, fluid…).
So this is the opportunity to show you how to change your bearings by yourself. The operation is neither long, nor complicated. You can get a precise idea of it with the following tutorial. On the tooling side, nothing really exotique. What you may probably lack is a bearing press, but I show you a way to make one for peanuts.
- Tool to remove the bottom bracket cups (optional but I strongly recommand it)
- Tiny flat screw driver
- Nail punch
- Bearing press (see at the end the method to make a press for nothing)
Dissassembly of the old bearings
- We start by removing the crankset. Sealings come automaticaly. I recommand to dismount the cups to be more confortable.
- We remove the circlips with the tiny flat screw driver.
- Now it’s time to take out the bearings (most painfull step). Bring your nail punch, et tap the hammer against the interior part of the bearing and try to spread the hits so the bearing move evenly. We can help ourselves with a tissue to hold the nail punch in place. If you have a headset cup remover, it can be helpfull. In my case, the left bearing was easier to remove than the right one.
Mounting the new bearings
- Once the old bearings have been removed, we can clean the cup, grease the things a little bit, and press fit the new bearings with the bearing press.
- We put back the circlips. They are used as stops for the bearings. So you will have to push them a little until they in contact with it.
- Now we need to tune the position of the inner cylinder taker in the left bearing. You need to push it (it moves quite easily with gentle hammer taps) until the star sealing isn’t in contact with the cup.
- Finally you mount the cups and set back the sealings and the crankset.
How to make a home-made bearing press
We need three ingredients : a threaded rod, bolts, and washers.
Threaded rod : Less than 3€ in zinc-plated steel, knowing that we will just need a tenth, and the rest will serve us for an other work. We choose the highest diameter possible as long as it fits the bearing inner diameter that you want to press fit (22mm for a Sram GXP left bearing, 24mm for a Shimano, 30mm for a BB30 etc…). We also keep in mind that this press could be needed for another job, like hub bearing replacements, so we choose the diameter consequently.
Bolts : Less than 5€ in a package of 5 or 10 pieces… We need at least two of the same diameter as the rod. Eventually a third one can help to hold the washers in place.
Washers : Less than 5€. It’s not the easier to find. We need to find washers with a even or higher diameter to the rod. The nearer the diameter the easier it will be to center the washer. For the outside diameter of the washer, we are looking for something equal or lower than the outside bearing diameter. If the washer is only in contact with the lower part of the bearing, there is a risk to split the bearing in two parts. Generally, on a new bearing that we press fit in a clean part (lightly greased), operate on the lower part does not pose a problem.
Once all the material is gathered, we can assemble all the parts as follows :
I put two bolts tighten one against the other at one side to create a fixed point.