BB/Crank Install MTB 73mm Shell - Have I got it right?
Discussion
Having just built up my Highball, my one concern is as to whether or not I have installed my BB / Cranks correctly.
The Shell measures 73mm, I am using a SRAM GXP BB with SRAM GX Cranks (8mm / 10mm hex bolts).
I didn't get much luck at the time when looking for install info on SRAM's site so installed what I thought was the correct method, 1 spacer on the drive side, installed the cranks and there appeared to be a 3mm gap, so reinstalled with 2 spacers (both on the drive side, probably should be one either side?) Should a 73mm have 2 spacers?
The SRAM cranks have 2 nuts, an 8mm and 10mm hex, am I right in tightening the 8mm down to a point where the cranks are held and spin freely (as opposed to being too tight) then torque the 10mm accordingly?
Before I put too many miles on the bike I want to make sure it is right....
Any help / advice is appreciated.
The Shell measures 73mm, I am using a SRAM GXP BB with SRAM GX Cranks (8mm / 10mm hex bolts).
I didn't get much luck at the time when looking for install info on SRAM's site so installed what I thought was the correct method, 1 spacer on the drive side, installed the cranks and there appeared to be a 3mm gap, so reinstalled with 2 spacers (both on the drive side, probably should be one either side?) Should a 73mm have 2 spacers?
The SRAM cranks have 2 nuts, an 8mm and 10mm hex, am I right in tightening the 8mm down to a point where the cranks are held and spin freely (as opposed to being too tight) then torque the 10mm accordingly?
Before I put too many miles on the bike I want to make sure it is right....
Any help / advice is appreciated.
I don't think I have any spacers on my GXP 73mm BB with XX1 cranks. I have a Sram maintenance manual saved in my bike folder if it helps.
https://www.sram.com/sites/default/files/techdocs/...
https://www.sram.com/sites/default/files/techdocs/...
The 10mm hex is for the crank extractor, you shouldn't need to touch that one. GXP work by clamping around the non drive side bearing, so you can tighten the 8mm until you are tired. Adjust the chain line with spacers behind the non drive bearing. Get used to changing them, they are crap.
gazza285 said:
The 10mm hex is for the crank extractor, you shouldn't need to touch that one. GXP work by clamping around the non drive side bearing, so you can tighten the 8mm until you are tired. Adjust the chain line with spacers behind the non drive bearing. Get used to changing them, they are crap.
If I torque the 8mm hex up the cranks are too tight - I've got 1 spacer either side now, if I only have one spacer the crank axle is still partially exposed as above (but less so)...With no spacers (as pictured) I am able to torque the 8mm up and the cranks run smoothly - I just don't think the exposed axle is right...
Not sure if sram is different but shimano / race face etc threaded come with 3 spacers So they are able to fit 68 or 73mm shells, 68mm 2 spacers in drive side one on other, 73mm one on drive side so it compresses the same. Can't see how it for sram it could be difference, move spacers & will make your crank off centre
tjdixon911 said:
gazza285 said:
The 10mm hex is for the crank extractor, you shouldn't need to touch that one. GXP work by clamping around the non drive side bearing, so you can tighten the 8mm until you are tired. Adjust the chain line with spacers behind the non drive bearing. Get used to changing them, they are crap.
If I torque the 8mm hex up the cranks are too tight - I've got 1 spacer either side now, if I only have one spacer the crank axle is still partially exposed as above (but less so)...With no spacers (as pictured) I am able to torque the 8mm up and the cranks run smoothly - I just don't think the exposed axle is right...
gazza285 said:
That's how the GXP is, the drive side bearing is floating on the shaft, with a gap. If you put the spacer in, then you have no gap, and the crank is stiff to turn.
Thanks, so the picture above is installed correctly? Maybe I'll swap it back over at lunch time (racing tonight) - I just feel that gap is going to fill with crap... I could get away with one spacer drive side to reduce the gap without adjusting the crank position within the frame and which will reduce the gap.gazza285 said:
Google GXP bottom bracket gap, they are all like that. I've only got one bike with a GXP bottom bracket, I'm looking at swapping the cranks for Shimano...
Thanks again, my canyon has gxp but push fit and there isn't any/much of a gap there hence why I didn't think this was correct... Will have a Google now..Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff