Rear Derailleur and Shifters Question?

Question

Can i run a Sram X.7 rear derailleur with X.4 shifters or do i have to upgrade the shifters also??

Answer 1

A lot of people will tell you otherwise (they're wrong) but you can use that derailleur with those shifters.  What has to match is the shifters, which are indexed, and the rear cassette, which is spaced to match the indexing.

You can even mix manufacturers without any problem.  That is, not only will that X7 derailleur work with the shifters, but so will a Shimano or Campy rear derailleur.  Derailleurs have no idea how many gear choices they are making -- only the high and low stops, which are adjustable. The indexing to match the spacing comes from the shifters.

Answer 2

Bad Boy is wrong. You can use the shifter/derailleur combination you propose but you can NOT mix Shimano and SRAM nor SRAM and Campagnolo. All cassettes with the same number of cogs have the same number of space between them... unless you go back to the 70s and early 80s.

Although I concede that the derailleur has no way of knowing how far to move without the shifter telling it, SRAM and Shimano shifters pull different amounts of cable. This means if you were to use a SRAM derailleur and Shimano shifter and shift from 8 down to 1, the derailleur might only shift to 4 while the shifter reads 8.

This is like saying that a 26" diameter wheel covers the same distance as a 700C wheel in a full revolution. Just not true.