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Why can't I use a triple....BB w/double Crank?(7 posts)

Why can't I use a triple....BB w/double Crank?jvr-oclv
Jan 17, 2002 6:27 AM
Any big deal to use a bottom braket(BB-6501) for a triple crankset and install a double crank setup with it? This is all Ultegra stuff.
Not one that I've ever tried.nee Spoke Wrench
Jan 17, 2002 6:45 AM
I think that it depends on how pickey you are about how things look and perform. One thing is sure, you're going to eliminate any problem of your chain rubbing on the inside of the big chain ring. Going to look kind of funny though.
ChainlineMike Prince
Jan 17, 2002 6:45 AM
The triple BB may work, but your front chainline will be messed up as the BB will position the rings farther outboard than intended. Also, if you have a double front derailleur, you may not have enough "swing" to get onto the big ring.

It may work, but keep in mind that the poor chainline could result in poor shifting performance and will accelerate chain and cog wear due to the increased angle of the chain, especially when in the larger cogs in the rear.

If it were me, I'd spring for the $30 for an Ultegra double BB. Or use 105 if money is real tight. That's much cheaper than new chains and cassettes.
You can.grzy
Jan 17, 2002 9:18 AM
You just won't get the shifting to work quite as well. All the other comments are good. Would you be using a double or triple front der.? Ultimately you can try the setup and swap in the BB at a future point. the only down side is that you may have a few more nicks on you frame and crank arms from tossing the chain if you don't get it exactly right. A triple setup is more finicky to get right and the shifting isn't quite as spot on, but people on this board have done much wacker component mixing and reported good results. YMMV
Can you still buy just the spindle?cory
Jan 17, 2002 10:54 AM
You used to be able to buy just a new, shorter BB spindle, but the last time I did it was in the cup & cone days, when things were easy to work on. Shouldn't cost more than a few bucks, if it's still possible. Maybe www.loosescrews.com??
Unlikelygrzy
Jan 17, 2002 5:15 PM
No part numbers are listed under the exploaded view of the Ultegra BB on the www.shimano.com (europe section) - so it's highly unlikely. These newer sealed units are sold as sealed and complete units and I believe that their thinking is that you just by the whole new assembly. Shimano isn't into stocking, selling and managing lots of their individual parts. this is one of the big criticisms of them over Campy, with whom you can by virtually anything - for a fairly stiff price.

It wouldn't too hard to disassemble the Ultegra BB and swap spindles - assuming you had one.
for what purpose??? (nm)C-40
Jan 17, 2002 9:30 AM