Rear Mech for 10 speed Compact

jonrb101

I’m putting together a road bike with compact chainset (50/34), 10 speed Shimano 105 shifters and a 10 speed cassette (11/32) SRAM Apex, but I’m stuck on what rear mech will work? I understand I will need an MTB rear mech and was thinking of XT or SRAM X9 quality, but I see that these are now available in 10 speed as well as 9 – will 9 speed or 10speed, SRAM or Shimano MTB rear mech work equally well? Any advice please?
Cheers
Jon

PeterBL

You need a 9 speed top normal Shimano MTB rear mech. Sram or 10 speed will not work.

jonrb101

Thanks Peter,

Will SRAM (9 or 10) definately not work (I've been offered an X9)?

Which XT model? there appear to be a few (M770, M771, M772)

Cheers

Jon

PeterBL

Sram will not work. Their cable pull is completely different.

I'm not really into MTB-components, but generally there are two types of MTB mechs, Rapid-Rise or "normal". Normal mechs shift like road mechs, so if you release cable tension, you end up on a smaller sprocket. Rapid-Rise is the other way around. Release cable and you get a bigger sprocket/easier gear. As far as I understand, it would still work with you STI, but would change the function of your shifters. But I would just get a normal one.

maddog 2

+1 what Peter said

SRAM mtb mech won't work with Shimano shifters as the cable pull is different

You need a 9spd Shimano MTB mech

Both top normal and rapid-rise will work but top normal is probably preferrable, as it works the same as std road mechs.

Short cage will be fine. Long cage will also work but won't be as tidy.

This is what I would (and have) used. I fitted one to a mate's bike for the Fred Whitton. He was on a 9spd 11-32 casstte but it'll work on 10spd too.

http://www.merlincycles.co.uk/Bike+Shop ... ch_951.htm

jonrb101

Thanks both - excellent advice, cheers

ride_whenever

I'd go for the M772 (the shadow one) it has a much lower profile (sticks out less) and most importantly has far superior cable routing so you have much less of a loop at the back.

maddog 2

I've found the shadow ones a tad less robust on the mtb and have gone back to the conventional versions, but this probably isn't relevant on a roadie as it doesn't get any hammer.

AndyI

The Shimano 5700 105 medium cage 10sp rear mech will cope with a total capacity of 39, provided the rear cassette capacity doesn't exceed 22. If you've got a 50 34 compact at the front that's 16, and an 11-32 cassette will give you 21 at the back, total 37. So, a 105 5700 medium cage is what you should use. Don't try adapting a 9sp MTB rear mech, it could prove an expensive mistake.

jonrb101

Thanks again everyone. Andy, although the 5700 rear mech has a total capacity of 39, it also states a maximum sprocket of 28 - I would like to stick with 105, but all the advice is that it won't work and to go for an MTB rear mech which are designed for 32/34 rear sprockets.

Cheers

Jon

AndyI

Ah, sorry about that. You're quite right. Wiggle Customer services recommend using a medium cage MTB mech, and there's some useful stuff on Sheldon Brown, here: http://sheldonbrown.com/harris/derailer ... ml#shimano

Good luck!

AndyI

Ah, sorry about that. You're quite right. Wiggle Customer services recommend using a medium cage MTB mech, and there's some useful stuff on Sheldon Brown, here: http://sheldonbrown.com/harris/derailer ... ml#shimano

Good luck!