MTB 9sp Derailleur with 10sp Cassette and Shifters

TinyExplosions

Right, the touring plan is coming together nicely, but I've another question I want lazywebs opinion on...

Am I right in thinking that a Shimano 9sp Rear Derailleur isn't really 9 speed as such, that it's just governed by the shifters and cassette -as in if I have 105 Shifters, and a 10sp cassette, will it work fine with a nominally 9sp rear mech?

Ta folks!

bcmf

Tiny, I believe that once the shifters and cassette are same speed ie 9 shifters with 9sp cassette etc the mech , once its 9sp or 10 sp mech, it should work.

penexpers

I've done exactly this before with no issues.

Holyboy

Well as far as I'm aware(but don't take this as gospel as it seems hard to get good information on it) as the number of gears has increased the jockey wheel(guide pulley, tension pulley, what ever you want to call them) tooth width has decreased just like the front chain rings, so as to fit in between the chain links, so if you use a 9 speed mech with a 10 speed chain, if the wheels are wider it may push the links apart and the chain may break,this is my understanding of the whole issue but I'd like to hear others views on it.

cdaly_

That would be my understanding too but I thought 9sp and 10sp chains were the same width. It could be an issue using 8sp jockey wheels with 9sp chain. Mind you, even then I wouldn't expect much of an effect as the chain is under minimal tension over the jockey wheels so there wouldn't be any significant pressure to push the links apart.

Peterx

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Karma

so you could replace the jockey wheels at the worst...
got another build going al, will show it to you next week :P