tdh

I have a tune Bigfoot triple MTB square taper crank (the one with the 94/58 BCD). I intend to use it as 2x on a road bike with a Campagnolo 10speed setup. Tune recommends to use a bottom bracket with 107mm spindle for the Bigfoot 2x road crank and 113mm for the MTB triple crank. Any recommendations what to do in my situation? Should I buy a 107mm, 113mm or, somewhere in the middle, 110mm bottom bracket? If anybody has experience with that I'd appreciate your input. Also: any recommendations for a ITA/JIS square taper bottom bracket? Thanks! One more thing: I will have to cold set the rear triangle...does that influence the chainline?

FBinNY 

Working totally blind, follow the maker's guidelines. It's a triple so use the spindle made for triple.

However, if you know the specifics, especially chainring and crank arm clearance to the chainstay, you might pinch in a bit with a shorter spindle.

Note: spindle math can be tricky. Sometimes changes in length are taken on both sides, but not necessarily equally. Other times the difference is only on the right side, ie. going from double to triple. So you'll want to know not only the overall length, but also the right and left lengths.

tdh

Thanks FbinNY...I think I install them with a 117mm bb and then just measure how much clearance I have. How's it going in New Rochelle? Lived there until 2015. Still consider it home...

FBinNY 

Other than taxes it's been great for me. My warehouse was in Mount Vernon, so easy commute by bike or car. NYC is conveniently close, and it's a short decent ride to the great riding up county.

BTW if you left in 2015 you wouldn't recognize it now.

tdh

Yeah, taxes were one reason to leave. Particularly, after they capped the deduction of the real estate tax. That was just brutal; sold my house after that. But for me it was more important to get my daughter out of there when the kids started to stab and kill each other at the High School in 2014/15. But I loved the town. My wife worked in sports and I always got good tickets for the Yankees and the Cosmos. Lot's of riding up north. Brilliant. Once I retire I'll move back...

KCT1986

First off, don't know the specific of your crank.

You also didn't mention which positions on the crank you plan to use (granny/middle, or middle/outer).

Attached is the common Tange left/right specs of cartridge BBs, most Shimano cartridges are similar (0.5 - 1mm difference). Should give you an idea of comparative lengths.



About the effect of spreading the frame, the change can affect the position of the hub, and thus the cassette. This is dependent on whether or not spacers are added to the hub to match the dropout.

Your plan to test fit and measure is the best way to go. Measure the chainline, both front & rear (after spreading and fitting the hub).

tdh

Thanks, that helps. I plan to use the middle/outer chainring, hence the effort to use the shortest spindle possible, thus bringing the crank in a bit further. Im just not a very gifted mechanic (aka lazy and prone to hissy fits if things don't go smoothly which, of course, they never do with old frames an components) and try to minimize additional work. ;-)

grumpus

Assuming you're using the outer two positions and clearance is not a problem, you want to move them inwards by half the small-to-middle distance to centre the chainline, and assuming axles are symmetrical you want one that's the whole small/middle difference shorter than the standard triple. But you know what they say about assumptions.