SRAM BB30 on BSA frame: Who's done it?

Discuss light weight issues concerning mountain bikes & parts.

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by dwaharvey

Jooo, apologies: I agree "botch-job" is too strong a word for it. I think "uncharted territory" might have been a better way of phrasing it. We're both interested in finding the best balance of cost/performance/weight, and there's a lot of factors. I agree the Cannondale arms are over-priced, but weight-wise they're good, and the system is well-used even on BSA. S-works definitely seem like a great setup if you have one of the frame BBs you listed. I believe the RaceFace NextSL will retail for $500 so those aren't too terrible cost-wise compared to others (much better than Cannondale), and are a lot lighter than I believe Sram BB30 would be (Sram BB30 only seem to save 50g or so over their GXP alternative... which if so means they still aren't very competitive in terms of weight), and setting them up with proper chainline, etc will be straightforward.

I guess a big question for me is whether the Force arms might be lighter than eg XX1 arms. If so that might make them a more attractive weight and warrant the effort in getting them to work. But it seems odd that it would work on many frames: road Q-factors are often 15-25mm less than mtb ones (eg 140 vs 165) , in which case I would think the arms wouldn't clear the majority of MTB chainstays...

Question is, why are the Sram mountain cranks so heavy compared to their road ones? From this thread it seems like the Red crank arms in BB30 only weigh 370g, whereas the XX1 in this configuration (BB30 with spider) is 496g... That's a huge difference!

by Weenie

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by TripseV

I have tried to do this.

Sram Force CX1 GXP crankset on a 2015 Giant Anthem 27.5 that has a 88mm wide shell.

I was attempting to get a lower q-factor on a mountain bike.

The first issue, is that even though the CX1 crank has the same removable spider configuration as XX, X0 cranks, the width of the connection is thinner on the CX1, so a normal MTB Sram spider cannot be used. Also a XX spider and XX chainring will not fit on the CX1 crank, as the chainring hits the crank, the U factor is too small, it works with very large chainrings, such as 110bcd, but they are not practical on a MTB. This was solved going to a spiderless chainring - specifically using Absoluteblack.

The next problem, and most important, is that using a PF86 cup assembly in the frame, the cranks cannot be tightened to hold together securely, without compressing the bearing so much it cannot turn freely.

There is some speculation that using a BB386 cup - designed to work with a spindle width of a GXP crank, but with a spindle thickness of a BB30 (the bearings are very thin and retro fit into a GXP shell) - and some unknown long spindle BB30 crank will work.

Whether or not this would work well enough to get the desired q-factor of the CX1 cranks of 145mm is unknown.

For the amount of trouble it is, the XX1 crank with a q-factor of 156mm seems attractive.

On a side note, the Rotor 3D cranks look like they may work, but only if someone makes a spiderless chainring to suit it - 28t please if a manufacturer is reading.
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by freeriderxy

Hi guys :)

I ride my Lightning BB30 crank on BSA FS frame,with custom made(at home) BB cups.

Cups have 30,5 mm hole diameter,and axle is 88 mm wide,with custom double chainring,and the Chainline is 47 mm.

BE a bike raider ,NOT a net surfer!

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