Bicycle Mechanics - can use 8spd der. on 9sp cassette?

Hi,

i have an xt 9 spd cassette, and am lookin to get a low cost short cage derailleur. I happened upon the Sora 8spd SS for a lightweight 20 bucks, and would rather spend that amount (as i will most likely break it sooner or later). Can i use the 8 spd on the 9 spd cassette?

I would think the width of the cassette is not much different, and the shifter does all the indexing...but i am admittedly a novice mech.

I just read up and found that i can't use a short cage on my xt cassette because its 11-34, and no short cage can accomodate more than 30T. But i am still curious if an 8spd long cage can be used on a 9spd cassette...

A couple of guys have tried it and it worked OK even tho Shimano said no.

The width of the 8 and 9spd cassettes is the same, hence either der would work, if the cage is compatible. There are two variants of long cage, one designed for road triples which stumble between 28 and 30T and a longer
cage for ATB triples upto 34T. The cage is mostly to wrap up chain but has to clear the largest cog, road triple rear der don't quite reach that far. Steve

Apart from the first-generation of Dura-Ace 8-speed derailleurs, all current (post-1997?) derailleurs work on 7 speed, 8-speed or 9-speed systems. Maybe even on 10-speed systems. It's the levers that are indexed differently.

Obviously, a short-cage derailleur will only work on 12-25 ... or 18-32, so it might work in an emergency, providing you make sure to avoid both extremes. That might save you if you need to buy a derailleur while touring in Labrador City, but let's say it's not recommended for a bike with wide range.

Regards,

The only problem I see is with the indexed shifting..But I'd give it a shot before I said no.

It has been my experience that a indexing 9 speed shifter will not work real well on a 8 speed cassette.

That's a difference with the shifter, not with the derailleur. On a 9-speed shifter, clicks are closer to eachother.

Regards,

Originally posted by mgagnonlv
That's a difference with the shifter, not with the derailleur. On a 9-speed shifter, clicks are closer to eachother.

Regards,

Yes, hence my post in this thread.

The derailleur does not know whether it is on a 9sp. or 8 sp.
Derrailleurs just have a set distance they travel (which is adjustable by the limit screws) It is NOT indexed at all, only the shifter is...basically all other drivetrain components are interchangeable. I have heard the rumors that they won't work and aren't compatiable, but I have not had any problem with any such combinations of parts. I am not a professional, but I have built 10 or so bikes in the last couple of years, and have mis-matched parts on several occasions with no problems. As long as your shifters have the same number of clicks as you have cogs on the cassette...you should be fine.

My bad, I though he was asking if he could use an 8 speed shifter with a 9 speed cassette. I misread the post! Sorry guys.

just to brag here, I got my 5 speed suntour derailler (1981) to index with a 7-speed freewheel...

everything else I would say has already been said...

I have also been able to use a six speed suntour shifter and derailler on an 8 spd. freewheel.

Like I said before...derailleurs don't know anything!! They just move a distance as set by the limit screws. It just doesn't matter to them how many gears you have.:)

I'm running 8 speed XTR short cage on my 9 speed road setup with no problems. As has been said, it's all about that shifter, not the derailleur.