7sp Cassette + 8sp Shifters. Mech Suggestions?

god1406

Hi all,

I have a new 7 speed Shimano cassette and 8 speed Sora STI shifters on a new-build project. For the rear mech, should I be looking for a 7 or an 8 speed?

Background Info:

I'm in the process of replacing the thumb shifters on my old Mercian with STI levers. Step one was to replace the 6sp cassette with a 7sp one and re-dish the wheel (only 125 OLN to play with). 7sp STIs are quite hard to come by/expensive, so I've gone for 8sp shifters (plus the new Soras I've picked up were £45!)

With an 8 speed mech, I imagine that I can just tune the limit screws to prevent it from searching from the 'phantom' gear. Any advice/experience would be appreciated here.

Thanks in advance.

Oli

nicklouse

Any within reason. 7/8/9 and even 10 road mechs have the same pull (yes there is an odd one that will not work, that can be read about on Sheldons pages as well).

Shame you did not ask first you could have had more gears if you had wanted them.

Have a read of Sheldons pages in my sig. The cassette pages would be interesting.

god1406

Thanks for the reply Mr Nicklouse, that broadens my mech options

It was a push to get a 7sp cassette in place of the old 6sp, without looking into stretching the frame and buying new wheels.

I'll consult the oracle that is Sheldon Brown.

Cheers.

drlodge

I have a 7 speed cassette (using sprockets off a 9 speed cassette), 9 speed chain, 10 speed chainset, 10 speed rear deraileur and 8 speed shifters. Lots of options are possibe, the main constraint being that your shifters neds to be compatible with the spacing between the sprockets (7 speed is 5mm, 8 speed 4.8mm so they work). No issue if using non-indexed shifters.

I did wonder if I could get more gears e.g. using 8 of 9, or 9 of 10. However from Sheldon's crib sheet these options would require a slighter wider overall cassette width, and as I have to use the two smallest sprockest off my 7 speed Dura Ace hub which are wider still than 8 or 9 speed, I don't think I'd have enough width.