Today we're examining the process for changing bearings in a SRAM DUB BB30 mountain bike bottom bracket. It's likely that many of SRAM's DUB BB will follow a similar pattern, so this post may still be useful even if you have a different model.
Puller Selection
We currently offer three designs of bearing puller; the wind-out type, the blind wind-out type, and the tap-out type.
The wind-out type needs access to maneuver the tool's inner drift behind the bearing. Unfortunately in the case of this DUB BB there is a flange that prevents access behind the inner race of the bearing. Also, the diameter of the BB around the outside of the bearing is under 44mm, so there isn't a surface for the tool's 44mm ID cup to rest on. This tool therefore isn't suitable.
The blind wind-out tool suffers from the same problem with the 44mm cup not having a surface to sit on around the outside face of the bearing - a common problem using wind-out tools with outboard-style BB (the BB sinks part way into the cup):
The simple tap-out puller is therefore the best choice in this case:
Note that all of these pullers are primarily designed to remove the bearing from a BB, rather than to remove a complete pressfit BB from a frame. However, the tap-out puller may remove a complete BB before the bearing is removed. That's OK, the same process can then be repeated a second time to remove the bearing from the BB. In this example however the BB is already out of the frame.
Removing the Bearing
SRAM's DUB standard uses a 29mm BB and crank axle. However, in this case it isn't actually a 29mm bearing, it's a 30mm bearing with a plastic bushing/seal fitted to the inside to reduce it to 29mm. This bushing isn't easily removable by hand. Instead, we can use the 29mm tap-out puller to remove the bushing in the same way as we would remove a bearing:
The bushing is quite easy to remove this way and it was possible to simply hold the BB in one hand while tapping the tool out with the other;
Next we must remove the bearing itself. As noted, the bearing is actually 30mm ID rather than 29mm. Ideally a 30mm puller would be used, but in a pinch the same 29mm tool can expand far enough to be used. Over-expanding the tool will reduce it's lifespan, but may be worth it for occasional use.
Supporting small parts can be a challenge; we're using the open jaws of a vice to support the BB (the vice hasn't actually been tightened on the BB). We've applied a layer of thick duct tape to the vice jaws to reduce marking of the BB's anodizing:
The bearing in this case is found to be marked as 6806W6LHV (30x40x6mm). This is an obscure size, perhaps bespoke to SRAM, and not to be confused with the common 6806 (30x42x7mm).
Installing the Bearing
Installing the new bearing is straightforward with a press. We've selected 30x40mm press drifts to match the bearing.
In this case we found that the beveled back face of the second drift sat better against the back of the BB:
Finally, after installing the bearing, the plastic bushing can be re-installed. Though it doesn't take a lot of force to re-install the bushing, it is somewhat reluctant to go in straight. Using 29x40mm press drift would make the job easier, but we found it popped into place reasonably easily using the flat back side of the same 30x40mm press used for the bearing:
