I’m looking for some opinions on a frame and fork I had made recently, I won’t name the builder as I want to give them a chance to rectify the issue. To be clear though, it is not a member of this forum.
I havent been able to fit a brake that doesnt foul the rotor, I believe it is because the flat mounts are misaligned. The company that built the frame have seen these photos and are saying that it is not a big issue but I disagree.
This photo shows the flat mount on the fork, I have clamped a ruler to the dropout and screwed a long bolt into the mount to show the issue clearly.
Brake surfaces can and should be re-faced, any reputable bike shop would have the tools for it (although the builder should maybe have done it already but mistakes happens)
For the thread, I would take it back to the builder as it would be a more involved process but if you want to do it yourself, I would use a thread insert, you can buy kits in any good hardware store or online.
The thread hole will need to be drilled out to a precise size (and straight, difficult to do by hand if the existing hole is not) and an insert added, the insert will have an ID thread of the same size as the original. This solution is often stronger than what it was before, it’s not difficult per-se but if your hole is not straight to begin with it may be a challenge to re-drill.
Agree it looks pretty terrible in the photo. I don’t understand how they managed to get the threads so out of line unless they drilled and tapped the mounts after attaching them to the frame, which would be an odd thing to do.
There is probably a specification somewhere in a Shimano document or something saying how cattywampus they’re allowed to be. I’m guessing much less than that. Might be useful to find that if they’re arguing about it though.
This would be the tolerances specified.
For those not familiar with geometric tolerancing: It means, that the tolerated surface (the flatmount bosses) have to be within two imaginary surfaces 0.1mm apart from each other which are perpendicular to the reference (the axle face in this case)
this is definitely way out of spec, and you’re right to be seeking a solution from the seller. however, this also might be solve-able by facing alone.
facing these mounts and then installing the adapter using very carefully chosen (length) bolts with a pair of spherical washers under the head of the bolt (between the bolt-head and brake adaptor ) might allow;
a) the adaptor to sit in flat on the mounts and hold the caliber in the correct plane/place ,
and,
b) the bolts to do up tightly and provide even (enough) clamping force on the adaptor so that there’s no issues with the caliper moving, either while tightening, or while riding.
even if that just gets you through until its a convenient time to have the builder sort it out properly, so you can “just run the normal bolts”
I had wondered that, I think the issue with a washer under the bolt head is that my flat mount calipers (GRX) have very little space for a larger bolt head on the upper bolt, lower is no problem.
The frame is going to the shop this week so I should be able to sort that. The fork I think I will send back as soon as possible, one issue with that is that I had a rack made to fit the fork, so if the fork needed to be remade I think they would need the rack to make sure they fit. Perhaps they would go down the helicoil route though.
