Crawf wrote:Yep try a few spacers.
Yep, that's the plan.
I spent this afternoon pulling the SLX crankset and BB out of my MTB, measuring, comparing, mixing and matching to see if I can bodge something up with a MTB BB (with/without spacers) and road crank.
Verdict is... no. MTB crankset has long spindle (and longer spline on LH crank), so requires BB outboard faces to be 5mm further apart. The MTB bearings are 1mm narrower (11mm instead of 12mm), but the MTB unit uses 7mm of spacers (or chainguide brackets etc) to get the additional 5mm. The cups have longer threads, and the plastic pipe is shorter to suit. Even without the pipe (which really doesn't have much function), there's not much scope for getting a wider chainline with any road/MTB parts mix.
But, from getting intimate with a few Hollowtech BBs, I reckon I could get away with ~2mm less spline engagement on the LHS crank, which is really the main implication of adding a spacer behind the BB cup. So I'm now on the scrounge for a spare spacer from my MTB buddies (has to be cheaper and easier than getting one mailed over from Belfast!).
I leant a friend my conventional BB tool, so I couldn't pull the old square-taper bits out of the frames they're in to check whether that's going to be a solution (although sourcing a long-spindle BB isn't a big deal if necessary).
Also, the option of denting the chainstay isn't entirely out of the question. The contact point isn't as close to the bridge as I had thought. I reckon the chainstays have ample strength (they're big for the sake of stiffness), so I'm not too worries about that. Just the process of carefully crushing my beautiful new frame...
All part of the adventure. If I wanted to be sure everything would just work, I wouldn't be building up a custom Chitanium bike...