So on Saturday, I managed to mess up my front brakes on my bike.

I got a cheap dial indicator and at first they were 0.070″ or so total indicated runout (on the cheap Harbor Freight indicator). Spec is something around 0.006″.

I tried to fix it by nudging the rotor on Saturday. It didn’t work, and honestly, I think I’m quite happy that I didn’t break my brakes even more.

I gave it a think this morning and I continued to cogitate all day on the matter. I figured out that it was the adapter ring between the hub and the rotor.

This is the one I messed up. It’s the piece that’s bolted to the hub and behind the slotted ring which helps run the ABS.

The other side doesn’t have the ring and I have an arrow pointing to it (and also outlined it in red).

Many, many whacks with a sledgehammer later (and a bit of tool abuse, unfortunately) it was back within spec. Back to 0.005″ TIR. You could think that this would lead to a drastic weakening of the aluminum, but the total deflection, once I’ve thought about it, was only around 0.020″. It’s small enough that I’m not at all worried about work hardening of the metal. Though I’m also really surprised it took a two-pound sledge to make it move enough.