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rd vs mt front derailleur

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rd vs mt front derailleur

Old 08-15-08, 05:35 AM
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rd vs mt front derailleur

I have a shimano 22-32-44 front derailleur (mountain) , & an online bike company told me I must use a mt front derailleur with that. Why won't the Sora triple rd derailleur work, it has a 22T capacity. I can't use a mt derailleur as it runs into rear tire. I only have 1" clearance between downtube and rear tire. Any solutions? Now I have a double rd front der and use just 22 and 32 rings
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Old 08-15-08, 06:33 AM
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The MTB front derailleur has a longer arm and therefor a different ratio of cable pull per shift than the road derailleur.

If you have road shifters then you can use the Sora, If MTB shifters then you need to get a "Flatbar road front derailleur". That will fit your frame without striking the tire but will have the proper ratio for the MTB shifter. The model # should be R443 or the newer R453. One source will be "Harris Cyclery" in Boston.

If it's just a question of the Sora cage being for larger chain wheels, then it might be possible to adjust it so that it works. The Sora will work with a 26-36-48 touring crankset without problem.

edit: The R443/R453 is still set up for the larger chainrings.
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Old 08-15-08, 06:34 AM
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Road front derailleurs are designed with their cage curvature to match a 52 to 53T big chainring and don't follow the tighter curve of a MTB crank very well. That said, they will shift MTB chainrings adequately if not ideally. Be sure to set the fd as close to the large chainring as you can get it, no more than 2-3 mm above the big ring.

In the late '90's Trek provided as OEM an RX-100 road front derailleur on an RSX triple bike with 46/36/26 chainrings and it shifted pretty well.
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