Rear brake pad clearance problem on '06 Specialized Langster I have a 2006 Specialized Langster, size 50cm. I replaced the brake calipers years ago with older-style Shimano 105 single-pivot sidepull brakes. 

The brakes have never been very powerful. Worse yet, the rear brake caliper fixing bolt seems pretty short and the brake sits close to the seat stay bridge, resulting in very little clearance between the pads and the seat stays. This severely limits which pads I can use because most pads bang up against the seat stays and ding it repeatedly.

I'm thinking of replacing the brakes with newer, dual pivot 105's for better stopping power. Is there a way I can tell if those brakes will fit or not before I order them (ie what measurements do I need to know and compare with the newer 105 dual pivots?). Also, I'm wondering if those brakes would provide enough clearance for 28mm tires. I would appreciate your thoughts.
Well, I went ahead and ordered some Shimano 105 dual pivot calipers. Unfortunately the rear caliper arms will not clear the seat stays. There's just no fixing it as far as I can tell. If I put on additional washers, the fixing nut will not thread onto the main mounting bolt far enough. I tried several sizes of fixing nuts and none of them will work.

I hope that I will be able to find some other brakes calipers that will work. If you know of any, please let me know!

***Update: I solved the problem by ordering a SRAM Force brake caliper set. Those calipers have a lot more clearance between their arms and the frame, and the bike shop filed down the main fixing nut so it will fit inside the rear brake bridge.