Hi, I bought Shimano road calipers for an older steel frame. The rear brake bridge hole is smaller than the Shimano recessed nut, so the nut won’t seat and the center bolt ends up too short to tighten (pics).
What’s the best fix?
• swap the caliper center bolt for a longer M6 one?
• use a smaller recessed nut / different mounting hardware?
• drill/counterbore the bridge (hard to access) — safe or bad idea?
Thanks.
by Comfortable-Ice610
5 Comments
You need a brake designed with a longer mounting bolt, they are available, but for nicer parts, you can use a front brake typically. I have drilled out frames in the past to accommodate the ressesed hardware, but it can be really difficult on smaller bikes.
Had a similar issue lately, and I believe both options are ok solutions: Getting a smaller recessed nut, or replacing the center bolt. I would try the smaller recessed nut first, because its slightly less hassle than replacing the center bolt.
There are different lengths bolts available. I suggest stealing some longer bolts from another brake. Or try finding them on Amazon.
The frame was designed with through-bolts in mind. I would personally ream the bridge out more to accommodate a recessed nut if the caliper I wanted to use used a recessed nut. I’ve done this scores of times.
This is gonna be an unpopular opinion, but you could drill a bigger hole to accommodate the fixing bolt.