Sticky Front Rotor

[Simonjjb]

Hi,

I had all my calipers refinished by PMB. The front Passengers 911S (1973) rotor is Binding to the outside brake pad. You can see the pad is touching in the attached photo. I can turn the disc by hand, but it doesn’t spin freely. The inside is ok. The Drivers side Rotor is fine - it turns easily without any binding. I have tried tightening the bearing as much as I can, but it’s as tight as it gets. On removal I noticed that the outside piston will retract a small amount - but after I retract it, it comes back out to where it started. What should I do? I have a call into PMB

[edmayo]

Tightening the bearing is not a fix. The pads should lightly drag the rotor, that's what the square o rings do. Often the problem is that the pads don't drag the rotor enough and then you have a long pedal. With usage the pistons will start taking a set further out to create that slight drag. Sometimes we will "advance" that piston set by removing the pads, then pumping the pistons out beyond the pad fitting, then push them back in just enough to push in the pads so that the pistons start further out. With usage that will eventually happen, we just try to speed up the process. Now if the pad is dragging the rotor so hard you can barely turn it then that's too much. Your pistons may still have the retractor washers in them which take a while to take a set further out on their spindle.

[Simonjjb]

Thanks very much Ed. It is dragging - but I can turn the disc with one finger on a wheel stud. It's stiff, but it's more than barely turning - it won't spin freely however. Maybe I just try it and see.

[edmayo]

Make sure you don't now have your bearing adjustment too tight. Back off adjuster until you have bearing play, slowly tighten adjuster until you just reach no play, then turn adjuster 1/8th turn further for slight preload.

[Simonjjb]

Make sure you don't now have your bearing adjustment too tight. Back off adjuster until you have bearing play, slowly tighten adjuster until you just reach no play, then turn adjuster 1/8th turn further for slight preload.

Done. Thanks Ed