Bicycle Mechanics - 7/8 speed compatability MTB

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all5pts
03-10-02, 08:25 PM
I destroyed an old acera 7 speed rear derailleur this weekend and am wondering if I can replace it with an 8 speed XT I've got. Will this work?

Thanks

John E
03-10-02, 08:36 PM
If you can run in friction mode, definitely yes, assuming the replacement has enough chain wrap. For index shifting, probably yes.
fubar5
03-11-02, 05:50 AM
Yup, you can run 8 speed. You could run a 9 speed if you wanted to. 9 speed or 8 speed compatability in a deraileur means it will shift for nine speeds, but if you don't use them all thats fine. My buddy put a 9 speed LX on his 1988 bike, and it works just fine.

RainmanP
03-11-02, 05:58 AM
My attitude on such situations is if I have a part I'll stick it on to see if it will work. Theoretically, because 8 speed cogs are a little closer together than 7 speed, one would assume you might have problems with indexed shifters, though as John E says, shifters that have a friction mode can work with many things. But it just might work. I have read that some Shimano 7 sp mtb shifters actually have an 8th click and will work with 8 sp systems. Hey, if you already have the part you can find out in about 10 minutes whether it will work or not. Even if it doesn't work 100 % it might work well enough to let you use a few gears so you can ride while you figure things out.