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Crazy low gearing question(9 posts)

Crazy low gearing questionGrand Pooh Bear
Aug 20, 2002 7:17 PM
Does anyone know if a "98 Shimano RSX front derailleur currently running on a 30-42-52 set up will work on an MTB set-up of 22-34-46?
why? are you trying to get to the moon? jk, nmcollinsc
Aug 20, 2002 7:40 PM
no: only up the Mount Washington Auto Road (nm)Grand Pooh Bear
Aug 21, 2002 3:42 AM
I don't believe it will...TJeanloz
Aug 21, 2002 4:09 AM
I think, but am not a MTB guru and don't know for sure, that you need a 'compact' front derailluer to work with anything below a 28 or so (it might even be a 30). These are the front derailluers with the really, really big inner plates. I'm reasonably sure that the RSX derailleur can't handle the job (I just don't think there's enough space in the parrallelogram to handle such a dramatic change.)
ThanksGrand Pooh Bear
Aug 21, 2002 4:22 AM
I had kind of figured that, but thought it was worth asking before attempting, just in case a minor miracle happened. So I will get an MTB derailleur to fit.
Not very wellSpoke Wrench
Aug 21, 2002 5:10 AM
The issue is the curve of the arc on the derailleur cage. The road bike derailleur is designed for bigger chainrings. When you try to use it with mountain chainrings, the chain drags on the back of the derailleur cage when you are in the granny ring.
re: Crazy low gearing questionChen2
Aug 21, 2002 5:40 AM
When I tried that on my wife's bike it did not work at all. Another problem may be how low the derailleur can be adjusted if you have a braze-on type.
Have you considered running a mountain bike rear cassette and rear derailleur? That works. You could run a 12-34 cassette with your 30-42-52 crank set.
~Al
Good idea.Spoke Wrench
Aug 21, 2002 5:46 AM
Just borrow the rear derailleur, cassette and chain from a mountain bike and replace them when you're through. ZERO COST. I like that!
I know you can swap the 30 for a 24, dunno about the 46cory
Aug 22, 2002 7:31 AM
Don't pay any attention to anybody--I'm running a 46-36-26 with an 11-28 on my Atlantis, and it works great. If people would admit how seldom they use anything above about 52-17, you'd see it a lot more.
Before I bought the Atlantis, I swapped the 30-tooth on my old RSX-equipped bike for a 24 with no trouble at all. Not sure if the front D. would handle a 46, but front derailleurs are cheap--you could replace it with something like an LX for $20 or so.