All these differnt numbers for a rear mech (shimano)

bwi

Got my self a new frame today and looking to replace the tired compnents. First up was the rear mech. I want an XT but there is the the 770 , 771 and the 772 , they all look similar to me. Whats is the supposed difference?

bri

stumpyjon

Actually there are 6 XT rear mechs as follows:

M770 - GS Low normal, short cage.
M770 - SGS Low normal, long cage.
M771 - GS Top normal, short cage.
M771 - SGS Top normal, long cage.
M772 - GS Shadow, short cage.
M772 - SGS Shadow, long cage.

Differences are:

Low normal, mech comes to rest in line with the largest sprocket on the cassette when tension is released, Top normal comes to rest in line with the smallest sprocket. GS is rated to work with a 33 teeth sprocket and SGS 45 teeth larfge front sprocket.

I think top normal configuration is more common (fitting a low normal mech to a bike that previously had a top normal mech will result in the shifter working backwards (which will take some getting used to).

Shadow rear mech is the new offering from Shimano, supposed to tuck up closer to the cassette then the normal XT mechs which is supposed to reduce the chance of it getting torn off by rocks etc. Shadowmech is top normal.

Cage length choice is dependant on your gearing set up, I think long cage is normal if you have 3 sprockets on your crank and short cage if you have 2, but I stand to be corrected on that.

If you want more detail (or to check I've got it all right ) heres a linky to the shimano website, click the mountain bike tab for a world of fun and part numbers :twisted:

oops forgot the linky

http://cycle.shimano-eu.com/catalog/cyc ... anding.jsp

bwi

thanks for that

At least i can try and sort out which i sright for me now

bri