Bicycle Mechanics - Rear brake shoes brushing against seat stay

On my Cannondale 2.8, brand new 105 rear brake calipers are having a problem. When installed, the brake shoe, metal/plastic that holds the pads, is rubbing firmly against the seat stay on both sides. How do I get rid of this problem?

Do I need to install a really thick washer on the caliper installation bolt?

Edit: Here are the pictures:

Rear Brake 1 (http://160.129.141.112/photos/rearbrake.jpg)
Rear Brake 2 (http://160.129.141.112/photos/rearbrake2.jpg)
Front Brake (http://160.129.141.112/photos/frontbrake.jpg)

Did you buy the set of brakes, or just one?

I bought a set, the front one is fine, the rear one has problems. I also noticed that front calipers have longer bolt than rear caliper. Have I got it reversed?

, the brake shoe, metal/plastic that holds the pads, is rubbing firmly against the seat stay on both sides. How do I get rid of this problem?

By running a cable through to the brake and completely setting it up. If it's still rubbing when in ready to rock mode then you have a problem.


Pictures would help.

I bought a set, the front one is fine, the rear one has problems. I also noticed that front calipers have longer bolt than rear caliper. Have I got it reversed?


Its possible you could them reversed. Front brake caliper fixing bolts are usually longer than the rear because of the extra width of the fork. Read caliper bolts are shorter because the brake bridge is narower. If you have your front and back calipers installed correctly, and your rear brakes shoes still contact the seat stays, you may need to use just a thicker washer(s).

Yeah I had them reversed before and it wasn't working, but now the longer bolt caliper is in the front and is fine. I am just worried that if I used a big washer to create some space between the caliper and seatstays, I may not have enough bolt available for the nut (wrong term?) to be screwed onto it. I guess I will have to figure that out myself.

I will post a couple of closeup pics soon.

I had same problem. Fixed it by adding a second thick washer to the mounting bolt. That added enough extra spacing to make the brake shoes miss (barely) the stays.

It's not uncommon to have this interferrence. Add spacers until you just get clearance. A 2 mm or so spacer should be enough and still leave plenty of thread engagement. Longer recessed nuts are available if needed but they usually aren't for rear brakes.