2011 Specialized Stumpjumper comp carbon 29er rear XT brake installation

[velobaba]

I can't seem to get a Shimano XT 785 rear brake caliper to install with a rear 160mm rotor on a 2011 Specialized Stumpjumper comp carbon 29er.

Any idea on if I'll need some sort of adaptor kit to get the XT rear brake with 160mm rotor to work on the frame?
I don't think Shimano makes a rear post to post mount adaptor kit for the rear.

What is the default size rotor for the frame? 140mm?

Thanks,
Jalal

[gdw]

The hardtail 15.5 and 17.5cm frames were designed around 140mm rotors and the larger models 160mm. If yours is a smaller frame you'll need a 160mm adapter. Call a dealer and see if Specialized makes one or if there is a Shimano model available.

[velobaba]

I have a 19" frame.

Thanks.

[DRietz]

Jalal, if the caliper inhibits you from inserting the wheel fully, or the rotor rubs on the caliper once installed, you will obviously need an adapter. If the frame is post mount, it'll be this one: Post/Post Adapter (http://www.backcountry.com/shimano-sm-ma90-disc-brake-adaptor?CMP_SKU=SHI0547&MER=0406&skid=SHI0547-ONECOL-REAISOS160MM&CMP_ID=PLA_GOc001&mv_pc=r101&mr:trackingCode=A8691A26-A661-E211-A87C-001B21A69EB8&mr:referralID=NA&mr:device=c&mr:adType=pla&mr:ad=50060994277&mr:keyword=&mr:match=&mr:filter=92795797957&mkwid=sJw0ybcCg_dc|pcrid|50060994277&gclid=CPjG1svW68ECFUeEfgodCDEA3A)