Might have a stuck brake caliper

[FiveOJester]

I just finished installing new pads and rotors on my '95 530i. Brembo stock replacement rotors along with Hawk HPS pads. I broke in the pads per Hawks procedure (6-10 35 mph stops, 2 45 mph stops, let it sit for 15 min) and then took it out on a test drive. At higher speeds (50+) I notice a slight pull to the left. Wondered if it might be a caliper hanging up on one side so I did the "smell test". Stuck my nose next to each wheel after the drive. All wheels gave no smell except for the front left, which had a slight burnt odor. This leads me to believe that the front left might be hanging up. Any idea on how I might get it unstuck besides replacing it?

The old rotors were pretty worn and had ridges along the rim. On most of the corners the caliper slid right off, however on the front left I had to really work the caliper to get it off. Found out afterwards it would have probably been smart to open the bleeder screw to allow the caliper to move and let the old pad past the ridge on the rotor. This caliper did compress back in just as easily as the others using channel lock pliers, which is a little strange. I'd expect more resistance if it was binding up.

Thanks for any help.
-Dave

Edit: I also rotated the tires when I did the brakes. Swapped sides, not front/back. I noticed the right front tire had slightly uneven wear on the inside, which might account for this pulling to the left, however the car tracked straight before this. Haven't had the alignment checked since I bought the car about 4 months ago.

[Kalevera]

Dave, bleed the brakes and get rid of the HPS pads. They're shitty, dusty and have a short wear life. Hawk makes much better stuff. My vote is for the Raybestos QS ceramics. Everybody has their own favorites, though.

A hanging caliper will generate a lot of heat. Highly noticeable, especially after driving at high speeds. Most recently, one of my buddies had the DS front caliper hang on his '97 toyota camrything after it sat for 8 months. It got so hot that it melted the plastic hubcap.

Tire rotation could explain it, especially if the tires haven't been consistently switched. Alignment could also be slightly off, explaining the above....You won't know until you dig into it...

best, whit

[FiveOJester]

I've heard good things about these pads from friends so I thought I'd give them a try. I agree they aren't too great. Made the pedal harder and I lost some of the feel from the Jurid pads that were on there, however stopping power once warmed up is definitely improved. I like to save money where I can so I'll live with them until their life is up. We'll see how long they last.

I don't think that a caliper is dragging after all. While on the freeway the car wasn't really pulling in either direction and then started drifting slightly to the right so I think it's probably the tires and/or steering alignment.

While out on another test drive tonight I really layed into the brakes and actually got some odd noise from the front that I didn't get yesterday when I really got onto the brakes while breaking in the pads. It almost sounds like something mechanically clunking on the driver-side wheel. This was at low speed (about 15-20mph, and yes both thrust arm bushings were replaced 20k miles ago). I pulled off the wheel to check everything and all the caliper and carrier bolts are still torqued to Bentley spec. Everything else looks OK, no sign of excessive heat anywhere, again leading me away from a stuck caliper. The rotors & pads still look brand new. I'll try throwing some more brake caliper lube on the back of the pads and see what that does to eliminate the "shudder".

Also is Bentley correct in specifying no lubricant on the caliper slide bolts? This seems a bit odd as the calipers actually slide on them. My Mustang had a somewhat similar brake setup and it required caliper grease on the caliper bolts.

Maybe the brake pads just need more time to break in and I'm being way too anal retentive. :D

[Kalevera]

My experience with Hawk stuff comes from this board, installing them on various cars, and customer impressions, one of whom is a hobbyist/race car driver and jobber. He condemns the HPS but likes their other pads. I've installed and then removed (in favor of Akebono ProACT -- stocked by worldpac and therefore by most any parts source in the US) the hawk pads from a number of UUC Big Brake cars. The dust is horrendous. I'm sure they also eat rotors, as I've had to do a few of those, as well. I like saving money, too, but the most efficient way to accomplish that goal is to get the best information ("perfect" information, as we call it in economics) and act from that. Anything less is more expensive in the long term. 'Nuff said on that.

A brake pressure applied, low speed slopping "clunk" can come from two sources beyond the typical stuff. Bad anti-squeal gunk can do it (pad rattling around). I've also found the noise to be caused by loose upper strut nuts (NOT the collar nut, although the collar nut can certainly do it, as well). This can be a hard one to diagnose: the weight of the car has to be on the spring (so the car has to be on the ground) to work around the spring preload. Grab and shake the tire in and out. Like I said, it's practically impossible to replicate with the front end in the air.

We use a product called Plastilube on the pins. My understanding is that it is a BMW part, but I could be incorrect.

best, whit

[EURODENT]

I also did the same swap about 40 days ago and was having the same problem. My mechanic said that it could be the boot causing it to hang up due to age and wear.