Front pads dragging on rotors

#1

More so now with new rotors. For example, car still rolls, but spinning the bare hubs by hand requires a bit of effort. Have stock guide pins, which seem ok. What should I look at?

#2

Bolt the wheels on and see if it still rubs.

#3

If it’s more than one wheel and turbo’s idea doesn’t work, then it’s likely the MC.

My e28 had the same symptom and the problem turned out to be a failed MC. e28’s and e30’s have different booster designs, but similar MC’s.

#4

Gummed up pistons another possibility. Have you ever disassembled and cleaned/rebuilt the calipers?

It’s a moderate difficulty procedure. I would check that out before getting into the MC.

#5

How often are you guys rebuilding front calipers?

I suppose my question really comes down to this - how much drag is “normal”? If the answer is none or very slight, then I have something to address. OTOH, I can still push the car around the driveway and spin the front wheels (when mounted) w/o great effort. Pads are dragging but not close to binding.

Thx!

#6

There’s no right answer on how often to rebuild calipers. All of us are racing on 25ish old cars. Our calipers should have been rebuilt or replaced as part of the race car built. If a person doesn’t know if that was done on their car, then they should rebuild or replace them during winter maint or something.

Once calipers have been rebuilt or replaced, they ought to last a pretty long time. The rubber boots will go, sure, but that doesn’t deadline the calipers. 50 track days? 100? No right answer.

A person that has rebuilt calipers a couple times can do it pretty quick. Especially if they have a technique for getting the piston out, and have the knack for getting the boot on and the piston squarely into the cylinder. The first time I did it I had a helova time. It didn’t help that the Pelican projects book had it wrong. Someone that has not rebuilt calipers before should note that reman calipers are pretty cheap.

Re. how easily should a front wheel spin. Go put a torque wrench on one of your lugnets and tell us how many ftlbs it takes to turn your wheel. Choose a lugnut and orient the torque wrench such that the wrench makes a nice radius to the wheel center. For example, put the wrench vertical above the wheel and choose the 12 o’clock lugnut.

#7

Sounds normal to me, especially if you replaced pretty worn rotors. Go bed in the pads on the new rotors and report back. In my experience you should be able to hear the pad dragging a bit on the rotor when you spin the hub but you shouldn’t get any resistance, you should be able to grab a wheel stud and spin the hub around freely with the wheel off.

#8

Sounds normal to me as well.

#9

I have been struggling with dragging front brakes for 2 seasons now. Rears are fine. I have gone through various sets of caliper rebuilds with no luck. I tried some Powerstops from Rock Auto that I just installed last week with same issue at the track. I am guessing the next step is to replace the Master Cylinder? I have an original Girling Booster and Master Cylinder. I appreciate any thoughts.