Thread: Front brakes stay on afte release brake pedal Calipers or Master? Need brake expert.

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Greg,in most (not all) the rear chamber serves the front brakes.

Brake drag with power disc brakes front and rear could be caused by one or more of the following conditions:

Booster pin length incorrect
If the pin from the booster that pushes on the master is too long, the master will not return to the correct rest position when you release the brake pedal, retaining a residual pressure in the system. Try shimming the master off the booster about 1/32" and see if the drag disappears. [ basicly what you mentioned above ] If it does, remove the master and adjust the booster pin inward.





A pre-load pressure on the booster
If your pedal linkage binds it may retain a pre load pressure on the booster which causes the booster to apply pressure to the master.

Wrong master cylinder
If you use a drum master for disc brakes it will cause the front calipers to drag. A drum master has a 10 lb residual pressure valve in it that holds too much residual pressure on the calipers causing excessive drag.