2

I recently purchased a new carbon frame direct from a Chinese manufacturer (link to the particular frame here). The frame has BB86 bottom bracket. I am using the SRAM Press Fit GXP BB86 Bottom Bracket. Outside of the frame, the bearings seem to run smoothly when I move them around with my finger. However, once I press the cups into the frame, there is a significant grinding/drag present in the bearings. Here is a video that hopefully explains better what's going on.

I contacted the manufacturer of the frame, and they suggested that either the bottom bracket is broken, or has been pressed in "too hard". I'm relatively sure nothing is broken with the bottom bracket itself, since I purchased it brand new. I have also removed and reinstalled the bottom bracket several times with varying levels of force, with similar results. I am using the installation washers included with the Park Tool BBT-90.3 and a long threaded rod with two nuts on either end to install the bottom bracket. Any idea what's going on?

2

Bearings are never as buttery once they've been installed, they all feel rougher after they're put under pressure. I put GXP BB90's in my carbon 29er frame and it was the same, though not too bad. It looks like you've installed them properly, it may just be that the frame could be a bit on the tighter side. Riding the bike will loosen things up a bit though, take it for a ride then check the bearings again to see if there's any difference. Unfortunately there's really nothing else you can do about it except hope that it smooths out a little from breaking it in. Those bearings are a closed system, you can't adjust them. The only other solution is to try a different bottom bracket.

  • Thank you, I have heard the same advice from a few others. Hoping it'll smooth itself out. Cheers! – Ben Siver Nov 19 '14 at 18:10
  • I can pretty much guarantee you won't feel it once you get the cranks on. It tends to be one of those things you only feel when your fingers are on the bearing. – ShemSeger Nov 20 '14 at 3:35
  • So I did install the cranks last night, and the rotation of the crank arms seems noticeably tight. I made sure the crank is torqued to spec and there is no lateral movement of the arms. I took another video to demonstrate (youtu.be/U49cl_Gpfbk). Would this much stiffness still be considered normal? I don't have much experience with press fit bottom brackets, but it seems to me like something weird is going on. – Ben Siver Nov 20 '14 at 14:38
  • 1
    No I would not consider that normal, I'd consider that pretty bad actually. If I were in the shop I would try a different BB, or even a couple different BB's to see if it was a component issue or a frame issue. You could take it to your LBS and have them install it, they shouldn't charge you much if you just brought the frame and BB in and asked them to press fit it for you. Then it would be up to them to trouble shoot it, and they'd likely have a couple other BB's to test with it. – ShemSeger Nov 20 '14 at 15:14
  • 1
    @RobertKoritnik: turns out the BB itself was damaged, likely due to me installing it improperly. I'm thankful it wasn't the frame! – Ben Siver Apr 6 '15 at 17:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.