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Old 10-03-2012, 07:56 PM   #5 (permalink)
Frank Lee
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Originally Posted by Oelmensch View Post
Unfortunately, as they do not employ return springs and adjustment hardware like drum brakes, disc brakes will usually have some degree of drag when not engaged. Beyond the extended position of the caliper piston(s), there is nothing to relate the pad distance to the disc, so they always have very minor contact while not in use and applying a product to reduce that drag would essentially also reduce their braking effectiveness and thus safety.

As for the temperature of your front wheels, it is likely a combination of the wheel bearing friction, and hotter air exiting the engine bay passing through the your wheel wells on top of any heat being generated by braking that makes them feel warmer. If your front wheels are out of alignment, that could also contribute to tire temperature, but I wouldn't expect that to be significant at the wheel unless things were really misaligned.
On older vehicles the piston seal is supposed to retract a little bit on release. Some (many?) newer calipers do have return mechanisms.

Wheel bearing friction is for all practical purposes nothing, and wheel bearings aren't going to heat up noticeably unless there's something wrong with them i.e. no lube, or they are very, very heavily loaded.

Alignment has nothing to do with wheel temperature especially towards the hub.

If the front wheels are warmer than the back ones it is because of brake drag.

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