SRAM Road GXP crankset and aftermarket bottom brackets

[beardedwarbler]

I have a fairly new CX bike, with a SRAM Rival 1x Road (aka "GXP", sort of) crankset fitting into BSA 68 mm shell, that I use almost entirely for road. It has developed a dreaded creak. Internet sleuthing suggests the GXP brackets aren't great and my halfway-decent engineer mind agrees so I bought an aftermarket (not Hope) replacement.

The manual that comes with the replacement states, for a 68 mm frame, 2x 2.5 mm spacers on the cups and a wavy washer on the driveside of the crank are needed - as received, the bike had neither. No chance, the non-driveside simply won't install. From further sleuthing GXP isn't GXP, and the road spindles has a shorter distance between where the cups should meet the spindle (70 mm instead of 75 mm). Measurement confirms.

Even without the spacers however, if you fully torque the non-driveside the crank is utterly seized. The 8 mm NDS hex bolt that should be at 45 Nm needs to be barely finger tight to allow reasonably free movement. On inspection, the new BB cups are slightly wider than the old - that may be why. Adding or removing the wavy washer makes no difference.

This leaves me with two questions:

1) what the arsing frick are these standards, SRAM? I shouldn't have to find archived 2011-era manuals from a much later than 2011 bike to find that one BB compatibility "standard" is actually two. And who thought up GXP anway?

2) should I:
- reinstall the old BB and hope it wasn't the issue?
- perservere with a lightly-torqued NDS? A ride or two done so far without issue, though I'm not convinced it's solved the creaking.
- try a hope BB? Just about the only other aftermarket makers I'd trust, but still no guarantee.
- give up on SRAM and find anyone who'll do a non-GXP 1x chainset with a 44t chainring? Shimano only seem to do tiny MTB-geared setups. Plus this is the most expensive option.

Thanks and apologies for a needy first post.
Warbler.

 

[fossyant]

Praxis Works do their own GXP direct replacement and the bearings are much better. They are also replaceable. Comes with sized end caps for road or MTB. Uber Bike components also sell them.

PS you can regrease the SRAM bearings. Also as for the NDS side, look at the torque setting. GXP is flaming tight. I use a hex bit on a long lever and put all my weight in it. If you don't GXP creaks if you don't do it super tight.

It's the opposite of Shimano ones. Its to do with the different bearing diameters for the axel. 24mm and 22mm

 

[Jenkins]

Added to what @fossyant has said, you shouldn't need the spacers if fitting to a road frame, just the 2 cups (done up bloody tight) and the plastic tube.

 

[beardedwarbler]

@fossyant thanks, I'll have a look at Uber Bike's BBs (Praxis being somewhat difficult to come by currently).

To clarify, there are zero spacers currently installed, and just measured, the external (cup face - cup face) width is 95 mm. That is measurably wider than the cups they replaced.

Think I've just gotten wrongly-designed aftermarket BBs, and will have to try and return them with apprentice marks.

 

[fossyant]

I'm running Praxis with Enduro bearings. I've just replaced the drive side cartridge bearing as it's got rough (some shockingly muddy winter rides). Any GXP needs regular greasing, especially on an MTB.

 

[beardedwarbler]

For the benefit of posterity... I tried an uberbikes road GXP BB as @fossyant recommended, absolutely fine.

Nukeproof's GXP BB is NOT compatible with "road" GXP cranksets, with any combination of spacers.