Originally Posted by
prem205
.....why do they sell derailleurs that specifically say 6/7speed, 8speed, 9speed etc...if it doesnt matter?
My guess would be for sales reasons. It's easier to buy something if it says straight out that it will fit the rest of the stuff on your bike. Then as chains go narrower, there might eventually be issues with cage/pulley width. Haven't had any mixing every which way up to 9, but don't know about 10/11. Migh be a sneaky way to try to influence people to upgrade too. Apart from chains and cassettes, derailers are probably the first parts to go. so if you can't find "your" speed anymore, maybe you'll feel tempted to upgrade the lot of it.
Originally Posted by
prem205
And when you say capacity, you mean the derailleurs capacity to take up extra chain when shifting to smaller/larger cogs right?
Thats it. The bigger the span in tooth count the longer the cage needs to be to take up the slack.