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Drag on SRAM ceramic GXP BB

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Drag on SRAM ceramic GXP BB

Postby abb7 » Wed Feb 23, 2011 3:48 am

Hi all,

I just installed a new SRAM Black Box GXP bottom bracket with ceramic bearings on my Tarmac today. SRAM Force cranks, current generation. Since the frame is 68mm shell, I used the two spacers that are included in the box (you aren't supposed to use the spacers if the frame shell is 73mm). When I start to snug down the 8mm left crank arm bolt, there is a TON of drag in the system. Then as soon as the bolt is just snug enough that there is no play in the cranks, the system is so stiff that the arms don't spin at all. Literally not at all -- they don't move without significant force applied.

Now I admit that I do not have a torque wrench with me since I am traveling. No one has the proverbial "torque wrench wrist." But I can say that I have installed enough bottom brackets with torque wrenches that I am not coming close to the torque spec when this binding is occurring. This is happening early--the bolt is very barely snug.

I checked the seals and everything is in its proper place. I double checked the spacer orientation and they appear to be double-sided. I applied plenty of clean, high-quality grease.

I have heard that new ceramic bottom brackets take a bit of 'break-in' to limber them up but this seems even more stiff than just a break in period.

Any ideas?
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Re: Drag on SRAM ceramic GXP BB

Postby Ypsylon » Wed Feb 23, 2011 7:56 am

The only thing I can think of right now is that there's supposed to be a washer between the bb and the NDS crank arm, but you probably got that.
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Re: Drag on SRAM ceramic GXP BB

Postby Juanmoretime » Wed Feb 23, 2011 10:29 am

While your bottom bracket width is supposed to be 68mm it could be off. If its 68.5 it could be an issue. You need to start measuring. Had this frame been built up before?
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Re: Drag on SRAM ceramic GXP BB

Postby gregorythomas » Fri Feb 25, 2011 11:23 am

Check the instructions again- it vaguely states that for mountain bikes, you use spacers for a 68mm shell and no spacers for a 73mm shell. For road bikes, you never use the spacers.
Because of that, your bb shell + bearings is too wide, tightening the arms up is putting a side load on the bearings.
lose the spacers, and everything should be fine.

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Re: Drag on SRAM ceramic GXP BB

Postby bikericer » Sun Mar 06, 2011 7:30 pm

My thoughts exactly Greg. +1
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