Tuning the brake bias knob?

[Dan Sherwood]

I've got a 69 camaro that I recently replaced the dynalite kit on the front with a wilwood 6 piston superlite. The car stops much better, but after doing a few panic stops in an open parking area i noticed the front tires would lock up and leave black marks.

Upon checking the bias knob the shop had turned it all the way to the front disc. I run 11 inch drums in the rear.

I've backed it off 1 1/2 turns, but I'm curious at what point is the tuning correct for the bias?