Bicycle Mechanics - Compatibility: FSA road crank & BB to MTB?
Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.
Can someone give me some pointers on what issues I may have swapping a FSA Gossamer triple crank and BB to a MTB crank & BB? The bike is a Jamis Aurora Elite that comes standard with the FSA Gossamer and FSA Mega Exo, external bearing BB, but while that is fine for regular riding, the gearing is too high for touring, so I want to be able to change it to a MTB crank & BB.
The bike also comes standard with a Shimano CS-5600, 10-speed, 12-27 freewheel that will also have to go. The rear derailleur is an Ultegra triple.
Is the answer to go (for instance) to an XT crank, BB and freewheel? Might there be compatibility issues with the frame and BB? I've never done this before (you might have guessed) so thanks for any tips about where I could go horribly wrong.
08-19-08, 11:17 AM
a tripple road crank is still to high for touring? what size is the smallest chain ring? you could possibly find smaller chain rings that would do the trick without buying a new crankset.
08-19-08, 11:37 AM
A MTB crank will probably place your chainline further out than desirable, particularly if you get one with an external bottom bracket. Also, your current 10-speed shifters won't work with a 9-speed cassette (the only type available with a large cog bigger than 27T) unless you add a Jtek Shiftmate.
You could keep your current cassette and shifters by replacing the 30T granny on your current crank with a 26T which will give you a 26 gear-inch low gear and that's pretty low. An MTB crank with a 22T granny ring coupled with your 27T cog gives an even lower 22 gear-inch low gear.
The current granny on the crank is a 30:
Setup is 30/39/53. The 53 will not be useful and I'm tinking the 39 will also be high. I was hoping to change all the rings and keep the crank, but I haven't seen any smaller rings that are compatible with this crank.
Thanks Hillrider. Any suggestions regarding wo might make a compatible small chainring for the FSA crank?
08-19-08, 12:18 PM
The 30T granny has a 74 mm bolt circle and chainrings in this BCD are available from many sources down to 24T. Your two larger rings have a 130 mm bolt circle and 39T is the smallest commonly available and 38T the smallest that will fit.
Replace the 53 with a 50 or 48, the 30 with a 24 or 26, lower the front derailleur to match the new large ring and you should be good. A 12x48 high gear isn't that high.
Thank a lot Hillrider! I'll start looking for those rings and see what I can find. The shop I'm buying the bike from are pretty good, so they may even stock them.
I appreciate the help:)
Powered by vBulletin® Version 4.1.12 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.