Need a Front Brake Expert

[BobZ]

Front brakes are not releasing as quicky as they should. Master cylinder, return hole and all recently cleaned and looking ok.

Curiously, when rolling backward brakes release immediately. Any ideas out there?

Thanks.

[GILLY]

Would think more along the lines of a sticky pad, try yanking the pads and running a small wire brush, like a soldering brush, through the calipers where the pads contact the caliper.
Gilly

[BobZ]

[/Would think more along the lines of a sticky pad, try yanking the pads and running a small wire brush, like a soldering brush, through the calipers where the pads contact the caliper.

I'll give it a try. I was thinking along the lines of a sticky caliper but wondered why it wasn't sticking while rolling backwards.

[AntonLargiader]

Are they stock pads? They could be hanging up on the guide pins, especially if they are aftermarket pads without the anti-rattle springs.

[BobZ]

Probably BMW pads as they were installed 14k miles ago during a dealer service by previous owner.

I have since changed the fluid.

[dbrick]

Curiously, when rolling backward brakes release immediately.

The pads aren't retracting because a) the bores are less than mirror-smooth, and b) the piston seals are hanging up on the bore as they move in the bores.

The pads move laterally within the bores a tiny bit. When you move forward, the pads are pulled forward (laterally) in their bores as they follow the disks; when you move back, the pads move the other direction. The reason they don't hang up when you move backward is the "rear" portion of the bores is smoother.

If you go in there to smooth the bores, change the piston seals, too.

[BobZ]

David,

That makes sense. Sounds like a little caliper rebuild is in order.

Thanks.

[dbrick]

Let us know.

Another reason for non-retraction is hardening of the seals, so they don't stretch as the pads reach for the disk and retract by hysteresis when the hydraulic pressure is eased. It's another reason for renewing the seals.