Could this work? BB30 related.

[HeluvaSkier]

So last night I installed my SRAM S950 crank into my new winter training bike (Velocite Selene - sweet frame btw). After installing it, I got to thinking if it was a true BB30 crank or not. The spindle seemed much longer than other BB30 cranks I have installed. I did a quick measurement after installation and the installed S950 crank appears to be almost 20mm wider on each side than my installed SRAM Force crank. Strange I thought - but these cranks are designed to accommodate power meter installation, so the extra distance and spacers make sense.

It hit me this morning that the spindle might be long enough to fit into a standard bottom bracket shell with a Zipp VumaQuad bottom bracket installed. I think the only way it would work is if the pre-load adjuster on the non-drive side could be removed from the crank arm - but if that were possible - I think it might be able to work with a standard SRAM BB30 spacer kit in order to get the correct pre-load and spacing without the pre-load adjuster installed.

So I guess my question would be - is the spindle long enough in the first place and can the pre-load assembly be removed from the non-drive-side crank arm and spindle? If it would work, this would be a great way to use a really light, incredibly stiff crank in a standard BB shell without shelling out almost a grand for a VumaQuad.

I'm not confident that such a thing is even possible, but it would be really cool if it were able to be done...

[crumjack]

I'm of no help on your question but was wondering if you had a weight for the crankset???

[HeluvaSkier]

I think it was 660g... SRAM must quote the weight without the chain rings.

EDIT: I think it was actually 630 or 640g because with the bearings and other fixings the full setup was 690g... I wasn't gram counting when I did the build so I didn't pay close attention. Shame on me.

[HeluvaSkier]

So in pondering this a bit more and looking at the manuals for the Vuma BB30 kit, the regular VumaQuad installation, and the S900 crank installation guide I think this is possible. The big catch is if the entire preload adjuster can be removed. Obviously the adjuster will unthread, but the threads need to come off as well. If anyone knows - now is the time - before I go tear mine apart...

[HeluvaSkier]

Okay, I pulled the crank back off the bike and the preload adjuster slides right off the spindle - as does the spacer that sits between the nds crank arm and the adjuster. This leaves a 120mm long 30mm spindle. 90mm of the spindle is round and the 15mm on each end are machined to slot into the crank arms. This means (I would think) that as long as the bottom bracket shell width with Zipp Vuma bearings installed was less than 90mm that one should be able to make this work with a few spacers added for the pre-load. The spider on the drive-side appears to leave enough clearance for the cups if they were to be used (they likely use the same mold as the GXP version and then machine the spindle insert to accommodate the BB30 spindle).

So... does anyone know if the Zipp VumaQuad spindle is the same or similar length to the 130mm SRAM spindle? It would probably also be helpful to know the dimensions of the Zipp BB cups as well.

[HeluvaSkier]

Zipp Vuma Quad spindle length is 101mm. I do not know if that includes the part of the spindle that inserts into the crank arms though.

[luckysix]

Okay, I pulled the crank back off the bike and the preload adjuster slides right off the spindle - as does the spacer that sits between the nds crank arm and the adjuster. This leaves a 120mm long 30mm spindle. 90mm of the spindle is round and the 15mm on each end are machined to slot into the crank arms. This means (I would think) that as long as the bottom bracket shell width with Zipp Vuma bearings installed was less than 90mm that one should be able to make this work with a few spacers added for the pre-load. The spider on the drive-side appears to leave enough clearance for the cups if they were to be used (they likely use the same mold as the GXP version and then machine the spindle insert to accommodate the BB30 spindle).

So... does anyone know if the Zipp VumaQuad spindle is the same or similar length to the 130mm SRAM spindle? It would probably also be helpful to know the dimensions of the Zipp BB cups as well.

Any update on this? I'm interested in fitting my bb30 s975 crank on a BSA frame.

[luckysix]

Does anyone know if the BB30 S900 and S975 cranks have the same spindle dimensions? Rotor says their BSA30 bottom bracket will allow the use of a BB30 S900 crank on a BSA frame, but they had no info on the S975.

[markito200]

I did get my s975 BB30 crankset to work on a BSA frame, use the rotorBSA30 bottom bracket. You must remove all spacers including the preload assembly use a wavy washer for bearing preload and you will be good to go.

[mca56]

Has anyone fit the SRAM S900 or S950 crankset to the Zipp Vumaquad cups? It sounds like it should work, since it works with the Rotor BSA30 cups, but I can't find a comparison between the Zipp and Rotor cup dimensions to be sure.

[markito200]

it should work if you play around with spacers and wavy washer.