Ultegra 6500 cranks on a MTB

[p nut]

I recently purchased an old mountain bike (Gary Fisher). It will be shod with Rat Trap Pass or similar tire to use on chunky dirt rides. So I thought a road group would be best on it, and proceeded to purchase a set of 6500 cranks, forgetting about the V1/V2 differences. I realized my mistake after the purchase. The only BB that will work on my 73mm BB shell is XTR, which is rare and expensive.

Any of you know of another (cheaper) solution? Of course, option B is to sell it and purchase ST road cranks. But I like these cranks and would prefer to use them, if it won't cost me a ton to get it to work.

[peanutgallery]

You need more clearance, Clarence. A road crank will never really work

Both shimano and sram make an xc race oriented mtb crank with like a 28/40 or so set of rings. Probably your best bet

[Joxster]

I raced XC with a chorus chainset so I could run 53/39 and a 12-25 cassette. Don't see why an ultegra wouldn't work.

[p nut]

I raced XC with a chorus chainset so I could run 53/39 and a 12-25 cassette. Don't see why an ultegra wouldn't work.

The problem is the bottom bracket. V1 Octalink that would fit a MTB 73mm shell is very rare. Sounds like it won't work for this build.

But I will stick with road cranks. I'll start the search for square taper cranks.

[David Tollefson]

If there is clearance for the crankarms and chainrings (at the chainstays), and you're willing, you could cut 2.5mm off each side of the BB shell and just use the road BB.

[peanutgallery]

Now that is some serious commitment :)


If there is clearance for the crankarms and chainrings (at the chainstays), and you're willing, you could cut 2.5mm off each side of the BB shell and just use the road BB.

[oldpotatoe]

Now that is some serious commitment :)

Actually on an aluminum frame, not that big of a deal but with splayed for fat MTB tires, chainstays, clearance of rings and crank arms probably be an issue.

[David Tollefson]

Actually on an aluminum frame, not that big of a deal but with splayed for fat MTB tires, chainstays, clearance of rings and crank arms probably be an issue.

Obviously measure thrice, cut slowly.

[p nut]

Coincidentally, I found this thread searching on Google.

http://forums.thepaceline.net/showthread.php?t=136983

I wonder if the guy went through with getting the BB shaved down.

[zennmotion]

Coincidentally, I found this thread searching on Google.

http://forums.thepaceline.net/showthread.php?t=136983

I wonder if the guy went through with getting the BB shaved down.

Nope, the guy (me) never got brave enough to cut down the BB shell- on my Al frame it's a question as to whether there's enough material outside the chainstay to do it. I solved the issue with a dremel to an off-market (Token) Al/Carbon left crank arm that uses octalink V1/road- it works after grinding some metal off the inside of the crank arm where it was contacting against the octalink spindle. It's still working fine after 5 yrs of CX abuse, but not recommended, I just made a lucky (OK hooptie) fit. When it comes time to replace the cranks, square taper BB or a double MTB/73mm- there's more options now than there were a few years ago. But, a square taper is still a beautiful thing, so do that.

[Joxster]

I was on a Giant XTC with SIDS on the front and the bike was awesome, had a few twitchy moments but ran smoothly when needed