Why do my Saab's brakes hate me? (C900 content)

I've had this car for several years now, and the brakes have never been 100% right. Part of that was due to the cheap pads I threw in it at the beginning, and having solved (fingers crossed) the remaining problem at the back (bad caliper), I decided to put new Pagid pads in the front to match what I installed in the rear. There had been no existing issue with the front brakes, and the old pads showed even and equal wear. I pulled the calipers, cleaned everything up (rotors are really clean, pistons retracted smoothly and without effort), made sure the new pads fit properly and moved freely (this required a bit of dressing the edges of the pad backing plates), lubricated the sliding pins, and started installing the new pads. Left side was fine. Right side required a lot of persuasion to get the caliper over the pads and in place, as if the pads were a tiny bit too thick. With the upper bolt in place, I had to use a pry bar to coax the caliper over the head of the lower pin (the bolts screw into the sliding pins).

Unsurprisingly, all this produced some drag. The car rolls fine, but a test drive revealed a fair bit of heat being built up on the right front - not smoking, but hot enough that I wouldn't want to leave my hand on the wheel for any length of time, and that's after ~10 miles at ~45mph. Brakes are otherwise better than they've ever been in my ownership. Do I just keep driving it and let the pads wear down a little, or...?

That right front caliper may be bad, and wouldnt completely compress, and is now stuck.

I promise you it was fully compressed and is functional. I felt it bottom in the caliper when I pushed it back in. No pull when braking at all.

Did you push the piston back in and twist the seal? Some of those oddball cars have a flat face to the piston seal and ive seen them twist in the bore causing the piston itself to drag just slightly.

I don't think it twisted. I compressed it with a big pair of water pump pliers and watched it the whole way along. It's a pretty standard-looking Girling caliper, so I don't think there's anything too odd about the seal arrangement, at least not that I noticed.

02Pilot said:

I promise you it was fully compressed and is functional. I felt it bottom in the caliper when I pushed it back in. No pull when braking at all.

I have run into this, where there was enough muck in the bore that the piston bottomed out on the muck, not the caliper.

I got an additional 2mm of caliper retraction after removing the piston and cleaning the caliper out.

Pete. (l33t FS) said:

02Pilot said:

I promise you it was fully compressed and is functional. I felt it bottom in the caliper when I pushed it back in. No pull when braking at all.

I have run into this, where there was enough muck in the bore that the piston bottomed out on the muck, not the caliper.

I got an additional 2mm of caliper retraction after removing the piston and cleaning the caliper out.

Not saying that's not possible, but the feeling when it bottomed was very much metal-on-metal, not the sort of mushiness of hitting built-up crud. And visually at least, it was flush with the caliper body once compressed.

I have seen quite a few pads that were a few thousandths too thick due primarily to the paint on the backing plates. Note that the build tolerances are poor, proven by the fact that you had to clearance the edges to make them fit. Not a Saab specific issue at all.

In reply to TurnerX19 :

I have seen similar things but normally not on a good brand like pagid

If you want to know if its a caliper problem, take just your right caliper off and try to mount it upside down on the drivers side. If it slides right on its not the caliper. If it doesnt go on the left side components either, you definitely have a caliper problem.

The paint on the backing plates did cause some interference at the sliding contact points, in spite of the calipers being totally clean. I ground the paint down in those spots so the pads would move freely. I didn't consider that it might be contributing to the other fitment issue, but it's certainly possible.

Success! I pulled it apart again, compressed the piston, and carefully inspected where things were coming together. The problem turned out to be the outer pad dragging; there was plenty of clearance between the piston and the inner pad. I dressed the back of the out pad where the ears of the caliper contact it, refitted, dressed it some more, and finally got to a point where it didn't seem to be causing fitment problems or dragging. Another test drive resulted in nice and cool wheels all around, so I'm declaring victory. I assume something much worse will fail soon.