New brake pads and rotors are hanging up.

[Rick Lee]

I put new pads and rotors on the wife's Mini last weekend. We drove to dinner tonight and I noticed the stench of burning brakes. Left rear wheel felt pretty hot. When I was installing everything, it went back together pretty tight. Mini rear calipers have to have the pistons rotated and compressed together. I thought I had the left rear one compressed all the way, but it was still a tight fit with the new pads to get it back on the rotor and all buttoned up. Wheel didn't spin freely with the wheel bolted back on, but I figured it'd loosen up once I bedded things in and wore the paint off the new rotors. Anyway, I'm a little concerned that my wife has about 50 miles on them and the left rear one still seems pretty tight. Is this normal and, if not, how to I fix it?

[rusnak]

Not sure about the Mini, but if only one side is hanging, it could be assembly error. If both, then wrong pads or rotors.

[slakjaw]

You have a bad caliper. Seized up.

[Rick Lee]

I can't see how it's seized if I was able to get it to retract just about all the way. And it seems to be stopping straight.

[slakjaw]

The are supposed to suck back in slighty when you take your foot off the brake. This is one of the functions of that rubber seal in the caliper. I suppose you could try pushing it back in more but IMO it's a seized up caliper.

[Rick Lee]

Tell me more about how that seal makes the caliper suck back. Because when I compressed the pistons, I had to use a tool I rented from AutoZone that simultaneously turned the piston clockwise. While doing this, the boot tended to twist with it and that made me nervous. But I was able to straighten the boot out by hand enough that it wouldn't get scratched or pinched when pushing the caliper back onto the pads and rotors.

[Jared at Pelican Parts]

Originally Posted by Rick Lee

Tell me more about how that seal makes the caliper suck back. Because when I compressed the pistons, I had to use a tool I rented from AutoZone that simultaneously turned the piston clockwise. While doing this, the boot tended to twist with it and that made me nervous. But I was able to straighten the boot out by hand enough that it wouldn't get scratched or pinched when pushing the caliper back onto the pads and rotors.

Rick,

try pulling the e-brake handle up and down a few times. See if this frees things up. I ran into something similar with our own project MINI. Did you remove the lower caliper frames when you changed the rotors or just slip them past? Also, check the routing of the e-brake cables. sometimes they can twist when you put the calipers back on.

send me an email tomorrow and I can send you some pictures of the whole assembly.

[Rick Lee]

I'm not sure what the lower caliper frames are. I removed those two 7mm allen bolts under the rubber caps and then had to remove those two 13mm bolts to get that bar thing off that holds the pads against the rotor. I use the handbrake when I park. Are you saying I should pull and release it a few times while driving or sitting at rest? Thanks.

[speeder]

I'm familiar with the set-up of those rear rotors, (twist/turn while compressing), but there is no way that it's alright for one of them to be that tight. I've seen some pretty gnarly damage from stuck brakes up to and including setting the car on fire. Get it sorted-out pronto.

[Rick Lee]

Damn. This is my wife's daily driver and she can't drive the 993. I'll see if I can round up a used caliper locally tomorrow. But I don't know how the e-brake cable connects to it. Really don't want to mess with this anymore, but I guess I need to tear into it again. I didn't have to push too hard to get the wheel to spin when it was off the ground. And the new rotors were painted.

[Jared at Pelican Parts]

Originally Posted by Rick Lee

I'm not sure what the lower caliper frames are. I removed those two 7mm allen bolts under the rubber caps and then had to remove those two 13mm bolts to get that bar thing off that holds the pads against the rotor. I use the handbrake when I park. Are you saying I should pull and release it a few times while driving or sitting at rest? Thanks.

Did you fit the new pads correctly? There is a spring clip that fits over the piston. Not sure what you mean by two 13mm bolts. There is the caliper that bolts (via the 7mm bolts) to the lower caliper frame.

Give me a ring tomorrow and I'll go over it with you.

Pull the e-brake handle while the car is at rest. This resets the venting clearance.

[Gretch]

Not painted on the braking surface, correct?

re the hand brake, that is the mechanism that sets caliper piston spin out, so the pad stays close to the rotor.

If a caliper piston is hanging, it will hold the pad very near, in contact with the rotor and yeah it will wear prematurely and get quite hot.

Jack the car up and see if that wheel is moving freely or if the pad is still hanging on the rotor. If hanging, you need a new, rebuilt caliper....

You could try a bunch of things, like bleeding and resetting, but each cycle takes time and is aggravating when it doesn't work.

Wifes ride = new calipers, in my book.

[RoninLB]

auto parts store may have a set of rebuilt calipers in stock or they can order them

if you are doing one, do both

[wdfifteen]

Originally Posted by Rick Lee

Tell me more about how that seal makes the caliper suck back.

Not sure if it is your problem, but:

The piston has to move out toward the rotor in order to deform the seal as in the right hand drawing. If it was so tight when you put it on that the piston is not moving when you apply the brakes, there is no deformation of the seal and no force to retract the piston.

[stomachmonkey]

My Starion had calipers like that, hated them.

If the face of the piston has notches the pad may have alignment nubs.

1st time you pump the brakes to set the pad the piston can turn a bit and the nubs end up contacting the piston face and not falling in the notches.

Happened to me once.

Can cause what you describe.

[Rick Lee]

Jared, the 13mm bolts are what hold that bracket onto the wheel hub. And the caliper bolts onto that bracket with the 7mm allen bolts.

[Tim Hancock]

Without ever having worked on a Mini, my guesses are that it "could" be corrosion induced sticky caliper piston, but it also could be caused by burrs on the new pad tangs where they slide or corrosion on the mating surfaces or sliding surfaces of the caliper assembly. If it were my car, I would take it back apart and examine the new pads to see if they move somewhat freely in their troughs and depending on the caliper style, check to be sure any sliding surfaces are work properly.

My SIL's car had what appeared to be a stuck caliper that was actually caused by a burr on the new pad along with corrosion on the mating surface of the caliper. A few swipes with a file on both parts and the problem was fixed.

[Rick Lee]

Ok, just jacked up each rear corner and spun the wheels. They both spin equally freely, but not totally freely. I used my foot to give each a slight spin and they spun. So I don't know that they're really hanging up. And there is a slight burr of old silver paint on the edge of the pads. That might be causing the friction and stench. My wife works 10 min. away, so I'll tell her to check them again when she gets to the office.

[Superman]

I'm with Tim. I've seen calipers whose pistons cannot be fully retracted, regardless of the amount of force used, due to corrosion inside the cylinder getting wedged between the piston and cylinder. And then there is the surface the pads slide against.

But it sounds like your problem might be going away. If you can spin the wheel fairly easily, then the friction problem is minimal and perhaps fixing itself.

[Rick Lee]

Man, I sure wish every car's brakes were as easy to work on as Porsche brakes. I swapped out my rear Big Red rotors a few mos. ago in 30 min. flat from the time I pulled the floor jack out of the garage until I was washing up for dinner.