Disc caliper housing rubs on rotor
I'm building up a Specialized AWOL frame with a Rohloff Speedhub. The frame has post mounts for disc brakes, and I ended up buying a set of Avid BB7's. They are the brakes the complete bike ships with from Specialized, so I didn't plan on any compatibility issues.
Front caliper and rotor mounts up fine. Rear caliper housing rubs on the rotor. My first thought was to shim the rotor outward from the hub, but there isn't room there for shims, and it would raise the rotor above the inner guide circle on the hub. There is some play built into the mounting brackets for the calipers, but it doesn't allow enough room to move the caliper out of the way of the rotor.
One suggestion was to use a file to remove some material from the caliper housing to allow for more movement, but there isn't much material there to remove. That seems to be about the only option I can think of however. Either the spacing of the rotor on the Rohloff hub is atypical, or there is an issue with the frame.
Just wondering if anyone has run into this issue before, and what your solution was.
Andrew R Stewart
When disks were less common it was common that the rotor/caliper locations wouldn't play nice with each other. As these things have entered mainstream the tolerances have tightened up. Still there's an occasional problem. Some shimming of the rotor with thin enough shims to not loose the centering feature might help. Some filing of the caliper's mounting bolt slots might help. But also there's bending the rotor over (or should I say "aligning"). Like over dishing a wheel to make up for a non centered frame.
I'm not surprised at this problem. Rohloffs are not what Specialized intended, if I have my specs right. These hubs can be querky. Andy.
I have never been around a Rohloff hub, but know there are different dropout requirements on the NDS, or adapters to fit to a conventional dropout.
Apparently there alignment issues with the disc hub and conventional caliper mounts. I did a bit of snooping and I'd suggest you get ahold of these guys. Monkey Bone Post-Mount Brake Adapter for Rohloff SPEEDHUB - Cycle Monkey They are the North American Service Center for Rohloff. I'd bet they can help.
Thanks for the replies. I've contacted Cycle Monkey a few times during this project and they've been very helpful. This time they suggested using a file to enlarge the slots for the bolts on the calipers, but I'd prefer to avoid that as there isn't much material there to begin with.
I did find some shims on McMaster-Carr that I think will work to shim the rotor out. The rotor bolts are just under 8mm diameter, and the shims can't be wider than 12mm or they'll hit the inner guide circle. The shims I found have a 7.95mm ID and 11.12mm OD.
$5 for the shims and $10 for the shipping, but hopefully they get the job done. If not, there isn't a whole lot else I can do. The rotor/calipers are out by 1.5-2mm, and I don't think I can file that much material off the caliper housing.