Hi

Trying to swap out a crankset on a bike but having problems. I currently have an X1 crankset with a GXP BB. I’m trying to fit a Force CX1 crankset using the same BB. However, when I tighten the crank bolt (to fit the non drive side arm), it compresses the inside of the drive side spider and the mounting bolts against the outside edge of the BB causing it to lock in place. So it’s not rotating on the bearing. Hopefully that explanation makes sense.

So what’s the deal? Is there supposed to be some sort of spacer to keep the spider and BB shell apart? Or is there a different type of GXP BB that is needed (given that X1 is an MTB groupset and CX1 is a road groupset)?

Any ideas?

I’ve tried this using both a Race Face direct mount ring as well as with the original spider that came with the CX1 cranks.

After some google-fu it would appear that the issue is that road cranks have a shorter axle so the spacers that are used on the BB for use with an MTB crank dont get used for a road crank. I found this info from a few cycling forums but couldn’t find it anywhere on the SRAM website / tech docs.

Going to give it a try and see if it works. Will report back…..

Exactly as you say…

Road BB shells are 68mm wide, MTB is 73mm (though some are 68, but you use 2x 2.5mm spacers to make it effectively 73mm).

Seems to work. Shame there’s no such info in any of the SRAM docs I could find.