Will a 8 or 9 speed derailleur work on a 7?

I don't wanna invest a lot of money in my iron horse because I'm upgrading soon but the rear derailleur is pretty messed up so I need to replace it. But its hard to find 7 speed ones that are even half way descent. So if I get one for a 9 speed cassette can I just set the limit screws to fix the problem of the 2 missing gears?

 

make sure it is the same brand as your shifters so the ratio is correct, check out the take offs section at the path.

 

Yes, it will work. Your shifters are what determine where your shift points are. Just adjust it like you normally would a 9-sp der and you'll be fine so long as you keep sram with sram and shimano with shimano

 

Well my shifters are indexed shifters and they only allow up to 7 speed. So I'm not really too sure what I would do there to allow it for a 9speed.

 

Absolutly nothing, If you use a 9sp derailer for your 7sp, you will need to run a 9sp chain. The shifter is what decides how far the derailer moves, the derailer itself just does what teh shifter tells it to do.


Personally I would try to find an 8sp derailer over the nine speed. The seven and eight sp are the same thickness, so you will get better performance out of it.