rear deraillieur - help

[Stratton]

I'm a newbie to this group and would like some help with a small problem. I have a Shimano STX rear
derailleur from a 15 speed MTB, question is a) will it work on a 21 speed MTB? and b) it has a short
connection to the frame on the original bike where the 21 speed has a long one, will this make any
difference? Apologies for lack of technical terms.

MTIA

Irving

 

[GearóId Ó Laoi]

It should work. They all have the same pull and the same throw. I don't think the length of
connection will make a difference.

 

[Stratton]

Many thanks for your help, tried it and it seems to be ok.