Bicycle Mechanics - Swapping bottom brackets?

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tooth
08-20-03, 04:41 PM
Lately my road bike has been collecting miles and my Trek 4300 mtb has been collecting dust. So I've been thinking of turning it into more of a commuter style rig.
I've got an idea about changing the gearing, but I have no idea how easy/advisable it is: Can I swap out my mtb style bb for a road bike style bb? I'd like to run just two chain rings up front--something like a 46/34 combo. I don't see why I can't, but maybe someone else does?

John E
08-20-03, 06:19 PM
Why not just keep the 3 rings up front? I run a highly satisfactory 40 to 100 gear-inch half-step-and-grannie 48-45-34 / 13-15-17-19-21-23 setup on one of my Peugeots.

Particularly if your BB is British/ISO standard, you should be able to find a shorter spindle to give you a proper chainline with only 2 rings.
Dave Stohler
08-20-03, 06:46 PM
Changing rings is soooo much easier than swapping entire cranksets and BB's.

roadbuzz
08-20-03, 07:19 PM
Yeah! What they said!

I think you're gonna have a tough time getting a 46/34 combo in a double, but am not an expert in such matters. Why not work out the ratios you want, and see if you can't put it together with the BB and cranks you've got, changing rings and/or cassettes?
MichaelW
08-21-03, 03:24 AM
Specialities-TA do chainrings for any bolt hole in any tooth count. With an MTB chainset, 34/46 is quite possible. For easy riding on the road, I like a cyclo-cross setup with 36/48.