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SRAM GXP BB on Surly CrossCheck

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SRAM GXP BB on Surly CrossCheck

Old 05-15-15, 07:09 PM
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SvenSurly
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SRAM GXP BB on Surly CrossCheck

I've been having some trouble putting a new GXP BB on my Surly CrossCheck. Specifically, I can't seem to get rid of a small amount of play, even when the crank bolt is torqued to the max spec (plus a bit). I've done the whole remove-regrease-replace thing, but that hasn't yielded results.

When I first bought my SRAM crankset (a 2012 Rival, FWIW), I had the shop tech install it. He fought with it for quite some time, and when all was said and done, I noticed that he'd installed one spacer on the non-drive side. It gave me no issues, so I thought nothing of it. When I did the job myself with a new BB two seasons later, I noticed that the instructions called for no spacers for the supposedly 68mm BB shell on the Cross Check, so I left the spacer off. On a whim, just now, I added a spacer, which removed the play, but also seemed to push the drive-side out a bit, as it's now rubbing on the front derailleur a bit.

So my question is, is it problematic to just run with the spacer as is (one spacer ring on the non-drive side)? Should I follow the mountain-bike instructions and install both spacers? Does anyone know why a 68mm BB on a MTB gets spacers, while the same shell width on a road bike doesn't?
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Old 05-15-15, 07:17 PM
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Eric S. 
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I have Rival cranks on some of my bikes and haven't had any issues with play or needing spacers, but if a spacer fixed things on your bike once before I'm sure it's fine to run it again.

Just re-adjust the derailleur and enjoy!
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Old 05-15-15, 07:20 PM
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You don't think having the spacer on one side vs the other will wear out the bearings unevenly or anything like that?
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Old 05-16-15, 02:16 AM
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I ride an old Bridgestone MB-1 as a commuter with modern Deore XT cranks. The BB shell on the frame is road width, 68mm, but the XT crank spindle is for 73mm shells so I need to use 2 spacers. Because of chain line issues, I have both spacers (two x 2.5mm each) on the non-drive side.

The asymmetry bothers me a bit but I've been riding this setup for over 5 years and everything's running just fine.
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Old 05-16-15, 03:57 AM
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Are you running a Rival triple crank? If not, no spacers are needed in a 68mm frame. Have you tightened the crank bolt down to spec? Its more force than you might think.
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Old 05-16-15, 05:00 AM
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The GXP bottom bracket works by trapping the non drive side bearing between the crank arm and a shoulder on the spindle. If you leave out the bearing cover/washer with the spline pattern in the middle, it will have play no matter how tight you make it. Spacing the bottom bracket is also accomplished on the non drive side. Spacers on the drive side do nothing but move the bearing outward.

As for the difference between 68mm road and 68mm MTB bottom brackets, road cranksets are designed for 68mm bottom brackets and no spacers are needed. MTB cranksets are designed for 73mm bottom brackets, hence the need for spacers to achieve proper spacing with the longer spindle on a 68mm bottom bracket.
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Old 05-16-15, 09:45 AM
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Originally Posted by Wingsprint View Post
Are you running a Rival triple crank? If not, no spacers are needed in a 68mm frame. Have you tightened the crank bolt down to spec? Its more force than you might think.
No, it's the compact double. The crank bolt is actually a bit over spec at 41 ft-lbs (39 and change is supposedly the max), but there's still play. With the spacer, though, there's no play. I guess I'll just ride it and see what happens. Thanks!
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Old 05-16-15, 09:47 AM
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Originally Posted by dsaul View Post
The GXP bottom bracket works by trapping the non drive side bearing between the crank arm and a shoulder on the spindle. If you leave out the bearing cover/washer with the spline pattern in the middle, it will have play no matter how tight you make it. Spacing the bottom bracket is also accomplished on the non drive side. Spacers on the drive side do nothing but move the bearing outward.
The play was there even with the washer in place. It sounds like maybe my BB shell is just a bit narrow, so maybe the spacer was necessary to resolve that. That's the only reason I can think of as to why the spacer on the NDS bearing would resolve the issue. Thanks!
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Old 05-16-15, 10:29 AM
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Originally Posted by SvenSurly View Post
No, it's the compact double. The crank bolt is actually a bit over spec at 41 ft-lbs (39 and change is supposedly the max), but there's still play. With the spacer, though, there's no play. I guess I'll just ride it and see what happens. Thanks!
Using the spacer, does the bottom bracket spin freely? You want to make sure there is no preload on the bearings, or they could fail quickly.
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Old 05-16-15, 11:02 AM
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Originally Posted by Wingsprint View Post
Using the spacer, does the bottom bracket spin freely? You want to make sure there is no preload on the bearings, or they could fail quickly.
It did seem like there was a very little bit more drag than before, though nothing that was noticeable with the chain on. I guess it depends on how you define "freely." The cranks don't drop to vertical now with no chain on (i.e. 12 and 6 o'clock); they just sort of stay wherever they are. Is that an excessive amount of preload?

If it is excessive, I guess the question becomes, what's worse: the preload or the play with no spacer?
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Old 05-17-15, 03:03 AM
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That does not sound like too much preload (or in other words side load on the bearings). As long as the bearings are not binding up or are stiff to rotate, you should be ok.
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Old 05-17-15, 07:29 AM
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unlike shimano cranks, those cranks and campy cranks have no inherent lateral adjustability to compensate for BB width discrepancies. you must use shims. i would put them on the side that is least problematical.
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