Using spacers between BB and crankset on GXP

[Greenduck]

Hey everyone,

I have a question for all you guys.

I have a Pina with an ITA bottom bracket. I'm running SRAM eTap with a the Red eTap crankset and Quarq DZero powermeter.

I want a black BB but the SRAM/Truvativ black BB (non-ceramic) is not available in my country. Only the silver colored ones.

I have and older Shimano Hollowtech BB from when I had an Ultegra crankset installed and I have an adapter reducing the NDS from 24mm to 22.

However, the Shimano HT2 BB is narrower than the SRAM GXP BB which means the axle is about 3-4mm too long.

I know you aren't supposed to use any spacers with a GXP crankset but I have installed 2x2mm spacers between the BB and crankset to take up the 3-4mm axle. It might be better to do 1 spacer on each side.

I know this isn't the right solution but can it work? The crankset turns smoothly and everything. I can't feel any difference compared to the GXP BB and there aren't any play.

Can this work?

Cheers,
Jake

[2lo8]

Spacers won't do anything except be loose or interfere with the proper fitting of the NDS clamping down on the shim.

The only useful shim for this set up is a 24mm wave washer and whatever shims are needed to get the wave washer to compress on the DS, since BSA/ITA GXP BBs have a circlip on the NDS to prevent bearing drift, which Shimano doesn't need nor have. PF GXP BBs use a similar wave washer set up to prevent bearing drift, and a Shimano BB has effectively converted a threaded BB to a PF.

[grover]

Definitely don't add a spacer between the crankarm and the bottom bracket on the NDS. As 2lo8 said, it will just interfere with the appropriate capturing of the shim between the NDS crankarm and the stepdown from 24mm to 22mm on the axle.

As the capturing of that shim holds the crankset from any lateral movement you don't need spacers or a wavy washer with a threaded bottom bracket. They are required with a PF BB because in theory the PF cup could work loose otherwise (I guess the threaded BB could also unthread, especially ITA thread). You won't cause any damage adding spacers and a wavy washer between bottom bracket and crankarm on the DS. Just make sure the wavy washer isn't fuller compressed or you're crushing your bearings laterally.

The other option would be to add spacers between the bottom bracket shell and the bottom bracket cup. This would create a wider bearing stance on your axle and remove the excess axle visible on the DS. Note that every mm of spacer you put between the NDS BB cup and the frame moves your chainline an equal amount closer to the midline of the frame. So if you're happy with your chainline only add spacers on the DS.

[2lo8]

As the capturing of that shim holds the crankset from any lateral movement you don't need spacers or a wavy washer with a threaded bottom bracket. They are required with a PF BB because in theory the PF cup could work loose otherwise (I guess the threaded BB could also unthread, especially ITA thread). You won't cause any damage adding spacers and a wavy washer between bottom bracket and crankarm on the DS. Just make sure the wavy washer isn't fuller compressed or you're crushing your bearings laterally.

Shimano bearings are just press fit into their threaded cups, so running a Shimano BB is basically just converting threaded to PF. It's not the cups unthreading, it's that the bearings in the cups might drift as they're not actually designed to bear lateral load like that. Shimano cranks can only push bearings further into the cup and prevent the bearings from drifting out. It's not needed with a real SRAM GXP because those have a circlip.

[Greenduck]

Hi guys,

I'm sorry if I didn't made my self clear but I was only going to add spacers to the DS and from your answers this should work fine.

As grover suggested, I will add the spacers between the BB and frame instead when I get some, just to make the bearing sit a little bit wider.

Thanks for your answers

[hambini]

If you put all of the spacers onto the drive side I think your chainline will be out.

Hambini

[2lo8]

If you put all of the spacers onto the drive side I think your chainline will be out.

Hambini

It has no effect on chain line if it does not prevent the 22mm NDS from seating. Only the NDS has a effect on chain line for GXP.

[alcatraz]

I'm using a gxp crank on a shimano 24mm bb90 bb with a reducer sleeve(because I can find bearings easier). It works fine but it took a few adjustments.

The kit comes with a spacer and a wavy washer meant for the drive side I'm pretty sure. I didn't need the spacer since bb90 has a wider bearing stance. It's 2-2.5mm if I remember correctly.

In any case, it was hard to get set up. Use a rubber mallet when installing the crank so you really seat everything properly.

My crank appeared to bind when it really didn't. After riding with the wrong order of spacers the play somehow "accumulated" and allowed for the original order, that would bind the crank, to work.

The wavy washer is tiny and wont preload much, just keep the dust cap up against the bb. The trick is to get it almost flat. Don't leave play in the crank, not matter how small because it could result in dropped chains and bad shifting.

Anyway, it worked with the reducer kit for me. Just needed to hammer out the play to spin the crank smoothly.

Besides the dust caps are plastic/rubber and will flex a little. You don't need to rely solely on the wavy washer to keep things in place.

About chainline you could measure your Q-factor (crudely by measuring pedal threads to center of downtube/seattube and put the spacer on the side so that this distance comes closer together.)

If this were a race bike I'd maybe choose a gxp bottom bracket or really work with thin spacers/shims to get it perfectly preloaded.

[2lo8]

There’s no bearing preload on GXP. The NDS just clamps to the inner race of the NDS bearing. Wave washer is to prevent bearing drift on pressfits.

[hambini]

There’s no bearing preload on GXP. The NDS just clamps to the inner race of the NDS bearing. Wave washer is to prevent bearing drift on pressfits.

This is my point, you will have the 3mm of longer axle all on one side

You would need an appropriate spacer on the non drive side to even it out? However this is more complicated because the NDS is on a taper so you would need to move the bearing outwards, IE put a shim behind the threaded bit of the bottom bracket.

Hambini

[TheKaiser]

There’s no bearing preload on GXP. The NDS just clamps to the inner race of the NDS bearing. Wave washer is to prevent bearing drift on pressfits.

This is my point, you will have the 3mm of longer axle all on one side

You would need an appropriate spacer on the non drive side to even it out? However this is more complicated because the NDS is on a taper so you would need to move the bearing outwards, IE put a shim behind the threaded bit of the bottom bracket.

Hambini

Just typed out a comment that seemed to get lost in the ether of the internet, so apologies for brevity. Anyway, yes, I agree with Hambini about the best location to adjust Q-factor being via spacers at the threaded interface between frame and non-drive BB cup. There are too many factors between tapers and tolerance stackups to try to adjust Q at spindle. Having said that, I also agree with 2lo8 that a little preload can work wonders to prevent problems in the future. A hybrid system like this could work perfectly for 10k miles, or it could wobble, creak, and click from the first ride. Since the BB manu hasn't specced and tested the BB for use in and un-preloaded application, it is a good idea to keep a little inward pressure on it via the wave washer/spacer setup.

[osw000]

If you don't like the anodized look of Sram GXP ita BB you can get this one by cbear:

https://www.c-bear.com/en/products/bott ... a-sram-gxp

You get ceramic bearings and i guess is a bit lighter too.

One of the advantages of still using BSA BB's is that there's no need to be messing with spacers.

Enviado desde mi SM-J530F mediante Tapatalk

[sfo423]

Just looking up similar issue. I have a new F10 with a GXP bb installed and using Red 22 GXP cranks. It does not come with any washers or shims so I assume this is a simple bolt up? Slide nds arm on > give a couple taps with a mallot > torque bolt to spec.

Is that it?

There’s no bearing preload on GXP. The NDS just clamps to the inner race of the NDS bearing. Wave washer is to prevent bearing drift on pressfits.

This is my point, you will have the 3mm of longer axle all on one side

You would need an appropriate spacer on the non drive side to even it out? However this is more complicated because the NDS is on a taper so you would need to move the bearing outwards, IE put a shim behind the threaded bit of the bottom bracket.

Hambini

[TobinHatesYou]

Just looking up similar issue. I have a new F10 with a GXP bb installed and using Red 22 GXP cranks. It does not come with any washers or shims so I assume this is a simple bolt up? Slide nds arm on > give a couple taps with a mallot > torque bolt to spec.

Is that it?

You don't even need a mallet. Torquing the bolt down will apply more than enough forced to mesh the NDS crank onto the spindle. And yes, no shims or wave washers are needed. The crankset clamps around the cartridge bearing's inner race, which is fixed in place in the NDS threaded BB cup, which in turn is fixed in place in the bicycle frame's BB shell.

[sfo423]

Thanks. At ~45 nm it’s not as free spinning at my dura ace. A bit taught. I assume some riding will free it up a bit.

Just looking up similar issue. I have a new F10 with a GXP bb installed and using Red 22 GXP cranks. It does not come with any washers or shims so I assume this is a simple bolt up? Slide nds arm on > give a couple taps with a mallot > torque bolt to spec.

Is that it?

You don't even need a mallet. Torquing the bolt down will apply more than enough forced to mesh the NDS crank onto the spindle. And yes, no shims or wave washers are needed. The crankset clamps around the cartridge bearing's inner race, which is fixed in place in the NDS threaded BB cup, which in turn is fixed in place in the bicycle frame's BB shell.