I recently replaced the Master cylinder on my 2007 SS. every thing bled fine, but randomly, the rear brakes drag. it has been the left rear, then the right rear, then the left rear and right front. i took it to GM to have the Anti lock bled. they did the process three times and they still drag randomly. i have seen folks mention about the brake pedal being loose or fallen down a little. i was wondering if anyone has seen this and what the fix was. could the aftermarket master cylinder have a deeper piston depression where the pedal rod goes and is causing the Traction control to engage? i am going to put a spring on the pedal to help alleviate any possibility. the pedal (part you put your foot on) has approximately an 1/8th of an inch in movement, but could be from general wear. the car has 157,000 miles on it. i have replaced the rear calipers and all of the rubber hoses in the rear (prior to the dealership Anti lock bleed process).
any help would be appreciated as it is my sons daily driver and is currently undriveable when you cant predict the brakes dragging. it was mentioned to me about the wheel hubs (with the traction control sensors) may be at issue, but it happened fairly quickly after the master cylinder change. Ken

 

Bumpity bump bump. I'm having this same issue after brake master cylinder replacement. My front & back brakes are dragging. Did you ever find the culprit? Thanks