shudder under braking

For the first couple of laps, my Mysterian M2 has an odd low frequency shudder under threshold braking. It goes away once the tires get up to temp.

It seems to be coming from the front, but not 100% sure. I put a dial indicator on the outside of the drums, thinking they are not round.

Both rear drums runout is about ~.010.
Both fronts are ~.005

Is there a spec for this measurement?

Any suggestions?