Sram GXP Crankset issue (bottom bracket related)

[cogs19]

I recently replaced the GXP press fit bottom bracket on my Pivot Mach 429 Trail.

I just checked it today and it is already cactus on the drive-side - notchy and barely rotating. I've ridden the bike about 4 times since the change. The replacement went well and there were no signs of any issues. Though when it came to reinstalling the cranks I was surprised with the GXP preload system - or absence of one. Anyway I tightened it all up to 50nm and was surprised with how little spin I got when rotating the cranks. But I thought I should trust the instructions.

So I'm guessing somehow I am putting too much pressure on the drive-side bearings. Only thing I can think of is that I have added a drive side spacer (in between the wavy washer and the bearing cover) which should not have been used. The bike came with a spacer installed so I replaced like for like. My bike has a 92mm bottom bracket shell so perhaps no need for this spacer? I have boost cranks and I thought perhaps the spacer was there to accommodate the chain-line??

Here's the details of my bike which outlines the bb shell size:
https://store.pivotcycles.com/en/bike-m ... ilsSection

Thanks to anyone with helpful advice.

ps I have now installed without the spacer and there is a gap where it used to be. So the dust-cover will be doing all the work to keep out foreign bodies, though I'm not sure that was the purpose of the spacer anyway. But without spacer the cranks spin freely and there is no side to side play.

 

[moorey]

They can be very finicky with spacing etc...but without seeing in the flesh, I’m not going to try to diagnose.

 

[Jpez]

I run Sram cranks but in a threaded bb. I have a gap outside of the dust seal. Think I had the same rodeo trying to space it out so piffed the spacers. I just use a bit of thick marine grease to glue the dust seal on and it’s been apples for about 4 years of abuse.
tldr- gap is fine.

 

[moorey]

There’s a wavy washer that sits between crank and seal on some of the GXP BB’s to fill that gap and push the seal against the BB.

 

[moorey]

 

[Jpez]

Seems I got ripped off a wavy washer when I bought the cranks.

 

[cogs19]

Seems I got ripped off a wavy washer when I bought the cranks.

The wavy washer comes with the bottom bracket not the cranks (spacer too). I have a spare wavy washer if you're desperate to be part of the team - I will post it to you.

 

[cogs19]

There’s a wavy washer that sits between crank and seal on some of the GXP BB’s to fill that gap and push the seal against the BB.

Yep, that's what I read too when doing the research. It's just hard to see whether the gap is small enough for the wavy washer to be effective without the spacer. Or perhaps the spacer is too wide not to crush the bearings. I'm resigned to losing the spacer and will just load up on grease to keep the water out.

 

[moorey]

Seems I got ripped off a wavy washer when I bought the cranks.

Not necessarily. I’ve bought new BB’s that didn’t include one. I’m not guaranteeing that your only issue, by the way, but it sounds like it will fix most of the issue.

 

[Jpez]

The wavy washer comes with the bottom bracket not the cranks (spacer too). I have a spare wavy washer if you're desperate to be part of the team - I will post it to you.

All good mate. Like I said I’ve been running ‘the gap’ for 4 years with no issue and only recently needed to change the bb. Which didn’t come with a wavy washer.
thanks for the offer though.

 

[cogs19]

All good mate. Like I said I’ve been running ‘the gap’ for 4 years with no issue and only recently needed to change the bb. Which didn’t come with a wavy washer.
thanks for the offer though.

Maybe wavy washers aren’t required for threaded BBs? Anyway, thanks for the reply, gives me the confidence to ditch the spacer.

 

[moorey]

Maybe wavy washers aren’t required for threaded BBs?

I don’t believe so. Never came with mine. Bought a couple of PF BB’s for others, now I think about it, the one that was missing it’s was ‘new’ off FB, but the box had been opened.

 

[silentbutdeadly]

This is why I ended up with a couple of packets of Wheels Manufacturing BB spacers and wave washers for these damn GXP cranks. Three different spacer thicknesses, four different attempts at spacer combination over two weeks and finally, success.

Put simply you need a thinner spacer because your new BB takes up slightly more crank spindle than it used to...

 

[The Duckmeister]

The GXP system - threaded or press-fit - relies on clamping the inner race of the left side bearing between the crank arm and the step on the spindle, so the right side is essentially floating. As such, it is very sensitive to matching the assembled bottom bracket width to spindle length. If the bottom bracket assembly is too wide (excess spacers for example) the bearings will get crushed/overloaded before the spindle step clamps up properly.

 

[Nambra]

Further to Duck’s explanation, I’ve got a Wheels Mfg threaded GXP BB with an AC bearing on the drive side. IIRC, you need enough spacers between the BB shell and the drive side crank such that the wavy washer just flattens when you tighten up the non drive side cranks to properly pre-load the drive side AC bearing. For a standard radial drive side bearing, the wavy washer serves to hold the dust cover against the bearing, but is still a good indicator of sufficient or too many spacers. A slight gap is ok too, as @Jpez notes.

 

[tim3638]

I have had difficulty setting up my gxp cranks/bb compared to my shimano cranks/bb but persist with them because I have a 180mm set of GXP cranks that I like. In the past I purchased a multi pack of wave washers and I think I have 1 or 2 sitting in the shed. If this would help anyone to set up their GXP cranks correctly I am happy to post for free. PM me if interested.

 

[cogs19]

I have had difficulty setting up my gxp cranks/bb compared to my shimano cranks/bb but persist with them because I have a 180mm set of GXP cranks that I like.

I rode today without the spacer and my cranks felt so much smoother and more free. I’m now sure the spacer was added in error by the shop that built the bike up.