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I have bought a hope BB to go on my nukeproof mega, with a 73mm BB cup. The cranks are gxp type. I have installed the conversion kit to the non drive side as instructed. And one 2.5mm spacer to the drive side. When I come to install the cranks something seems wrong. To get rid of play in them I need to tighten them right up, to the point that the cranks do not spin freely?! Any suggestions.
Remove the spacer and try again. The way the GXP system works is the cranks only clamp on one bearing (the one with the adapters); there is supposed to be a gap between the crank and the cup on the other side.
Any lateral play you get will be solely from the NDS bearing tolerances/wear, and that will be mostly eliminated by using a wavy washer in the said gap.
l.e. This thread may help as well (not GXP, but similar issue): https://singletrackmag.com/forum/topic/race-face-cinch-question/
Just take the spacer out. I've got a Hope BB on both my MTB and Road Bike. I followed the instructions regarding the spacers and on both occasions they didn't fit properly! You just need to move the spacers around until you get it. It'll either work or it wont so keep going until you get there.
Silly question. This ‘play’. Is it actual float in the crank (ie, you can wobble it) or simply an observable gap on the NDS?
GXP is meant to have a pretty substantial gap between the crank arm and bearing cover on the NDS. Attempting to eliminate it will destroy the bearings in short order and lead to excessive tightness...
Vincienup. It the floating in the cranks. To eliminate it I have to tighten the cranks more which in turn make them almost lock up!
That shouldn’t be happening, obvs.
Back to square one then I guess and check tightening torque and install of the 22mm shims plus spacers. I’ve been misled by install instructions before and had a mystery uninstallable crank that turned out to be me misreading the comic style diagram regarding spacer use.
More spacers/shims will only make the problem worse if the crank is bottoming out on the DS cup.
The only possible place where shims would help would be on the Hope adapters if the crank arm bottoms out on the splines without clamping the adapters/inner bearing race - but I assume the width of the adapters is just right and you shouldn't need shims there.
My SRAM cranks on Hope BB bind a tiny bit, by which I mean if you spin them with the chain off they don't spin as freely as I'd expect, but still manage two or three revolutions, I think I read this was to be expected with SRAM/GXP and Hope BBs, but can't remember why.
I do know that I took out the wavey washer on one side on somebody else's recommendation which freed things up a bit.
Everything is set up as instructed by hope tech. Gxp adapter on none drive side. One 2.5mm spacer on drive side??
Are they cranks that you have reused?
Twice now I’ve had this issue, look at the drive side end of the axle and make sure you’ve not got a spacer or bearing seal hiding on there. Confused me till I realised my error!
All I can think of is the Nukeproof BB cup tolerance is out. Going to measure it when I'm home, I'm thinking it's slightly over 73mm. Might try without spacer on drive side. If not then God knows?
Just take a moment and try to forget about what you think you know about how a crank is supposed to work and understand how this one does. The Hope video gets half way there at 1:20 mentioning the solid connection of the cranks and NDS bearing, but goes on a tangent with the sealing tube sliding around; it is normal to have a gap on the drive side; without the slightest of gaps, the bearings will bind.
Once you understand how it's supposed to work, you'll know how to fix it and you won't have to try.