How do you know when your caliper is sticking?
 

I have seen several posts where someone said his caliper was sticking and then he did something about it. How do you know it's sticking? Is there an obvious drag? What if it's just sticking a little bit? Is there a test? Do you just spin wheels in the air? I've had cars where there seems to be some brake pad drag, so how can you tell the difference?

Comparative wear differences in the pads when comparing passenger vs driver side brakes.

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If one caliper is dragging, the pad and disc are heating. When brakes are applied, the front end pulls to the OPPOSITE side of the dragging brake -- because the dragging brake is less effective than the non-dragging brake.

A few years ago there was a burning smell I detected near my driver side fender - which originally I misinterpreted as some sort of electrical issue in the fuse panel. I tried identifying an overheated wire or fuse, etc - with no luck. I then continued searching and realized the smell was at the front wheel hub itself - stuck caliper. Rebuild of both front calipers and replacement of the 30+ year old soft brake lines fixed it.

Just talking. Heat is not a bad thing. Warm brakes work better than cold brakes. Sugarwood asks, what if it's dragging just a little bit? Can your statement be reversed?

With respect to kenith:

I see imbalanced pad wear regularly. Not 2013 BMW's but 2002 GMC Jimmys. Everyday, shiet boxes. I do occasionally see worn pads that are equal. It is refreshing. However, I check the slider pins and pad slide surfaces on all. If ok, I clean and replace grease. Can't economically check piston bores. I sure wish there was a good method to identify root cause aside from the obvious (e.g., you can't push the piston back in the bore.)

Drive around without using your brakes any more than needed. Take the rotor temps with an IR temp gun. The warmer rotor is on the dragging caliper.
Dave

+1 on the Infer Red heat gun. Drive around a bunch and use your brakes lightly. Read temps on all four wheels,
Mine were 107 on 3 wheels and 142 on the right rear. When I tried to pull the pads today, it was all I could do to get that one out.

Rebuilding the Calipers and new rotors and pads as well. Really the Pads weren't bad at all, had a lot of life left, but why not replace them "while I'm in there"

Bob Kontak: Hmmm. Never thought about it that way. My experience is with hitting the brakes hard and the car pulling hard to one side, and I found the OTHER caliper stuck. Rebuilt both calipers and never saw it again.

In answer to your query, I would expect the pedal-effort effect to be more significant than the temperature effect. I really don't have much to support that statement, outside of my personal experience as described above.

I occasionally stop the 911 and touch the hub part of the wheel, then tap the brake disks to see if there is any heat from dragging rotors. A quick and easy test.

Lots of those tests are great, especially if you touch each wheel and feel a much warmer wheel after stopping. If a front is sticking a simple thing I have had happen is just do simple stop holding the steering wheel lightly. The wheel will turn and car will veer. The good caliper will grab as it should pulling the car in that direction. The stuck one will not grab as hard letting that wheel roll.
Guess the same can happen in the rear but steering wheel effect will be muted a bit.

I could tell my calipers were sticking when I would come to a stop and then take my foot off the brakes, there would be no movement until I let off on the clutch and even then, I could feel a slight drag if I stepped back on the clutch.

I had a similar issue and found it was my emergency brake not fully disengaging. Using my infrared thermometer I found a very high reading on the drivers side rear brake. I took the rotors off and cleaned the E-brake and readjusted them. No issues since

or you could jack the car up and feel the drag on the suspect wheel...

I just went through this on my '76. Noticed a VERY slight pull to the right while driving. So slight I thought it was the road. Felt the wheels and the right front wheel was noticeably warmer. Got rebuilt calipers and flushed the fluid....all is well!

It was just a thought. When there is true sticking the rotors become blisteringly hot. No laser gun needed. Just feel the wheel. Too damned hot.

Heat aside, there is something wrong and that brake is not going to brake well, supporting your observations. If it can't back off, it probably can't go in.

Lots of good info. here so will only add that sticking pads often happen after a rebuild if the puck is not retracting smoothly back into the bore via hydraulic pull. Also, if you have older rubber lines one of them could be clotting up and causing you issues. Finally, until freshly installed pads and rotor surfaces mate up you may experience some drag, but usually not enough to pull a corner over as described.

In both cases you would want to pull the offending part and replace or rework, or let time bed fresh parts.

This.

Wear differences on the inner vs outer pads, is the car pulling to one side? Both pretty good indicators. Another way to tell is use an infrared thermometer to check the rotor temps. The hotter one usually has a caliper sticking.