I bought (what I thought) was a set of Ultegra 6500 caliper brakes from a "going out of business" sale at one of our LBS'. Little did I realize there's a difference in the pivot bolt length between the front and read caliper assembly. What I got would be considered two rear brakes as the bolt is fairly short, 36mm. Checking Shimano's TechDocs the rest of the caliper looks to be the same between front and rear. So I think I need to just replace the pivot bolt with the longer, 50.7mm, version.

Checking for the part, 83H 9803, online looks like it's not readily available in the US but it is showing up on some UK web sites with the price somewhere around $35. At this point going back to the LBS where I bought them is out of the question and I haven't tried checking with a local shop for price and availability.

I am wondering if it's possible to interchange the pivot bolt from a 105 caliper, Y-83J 98030, which is the same length and costs something like $20. Anybody know? The other option would be to get a longer pivot nut, but I'm concerned about safety issues running with a shorter bolt and making up for it with a longer nut.

The brakes I'm replacing are Tektro's and are so much like the Ultegra's. The pivot bolt is about 2", but I realize now I really need to check it as I have a carbon fork. If you have any experience disassembling/reassembling the caliper I'd appreciate any insights you might have.

Cheers!

A bike shop should be able to get one for you. I ran over a bucket bail the caught my rear spokes and locked up my rear brake. I bent the bolt. My bike shop got me a new one.