Front brake problem- caliper hang up? Long story...

[ultrasonic]

There has been an issue with my driver side front brake since I bought this car (91 Sport Sedan). When braking to a stop, there was a creaking or scraping sound. It is associated with the wheel rotation speed, i.e. the sound slows and stops as the rate of speed decreases and stops. The sound only happened under braking.

Oddly enough, it went away. There were a few other problems with the car which I related to the fact that it had not been driven much in the two years before I bought it. So I thought that the issue was some deposit on the rotor that I finally wore through. But then, the sound returned. Eventually I noticed that during or after rain, the sound was present, but it would go away after some miles of dry weather driving. At least I thought so.

Finally, of course, the sound returned and didn't go away. Also I began to notice how much more brake dust collected on the passenger side front wheel compared to the driver side front wheel.

So tonight I took the wheel off for a closer look.

It seems that the caliper was not sliding smoothly, so I removed the lower bolt. It had quite a bit of rusty deposits on it. I wiped it off and cleaned it with brake cleaner spray. Even after cleaning off the loose crap, the surface of the bolt is still somewhat pitted and rough. With the lower bolt out, and the caliper pivoted up, the upper pin seemed to allow smooth action of the caliper, so I'm assuming that it is ok for the time being. I cleaned the lower bolt as well as I could and applied some high temp grease to the smooth portion above the threads, and replaced it.

On test drive, the noise is completely gone. Also, there may be a noticable increase in stopping power. Could be my imagination, though. The car stops pretty straight without pulling significantly to either side, but it was that way before, too.

I think that the caliper sliding motion was hung up in such a way that the inboard brake pad was contacting the rotor with more force than the outboard pad. That would explain the lack of brake dust on the wheel. Is this a plausible explanation? Any brake experts care to comment?

In any event, I have already begun collecting parts to do the WRX front upgrade.

[LaureltheQueen]

any kind of petroleum anywhere near your brakes is BAD news

[evolutionmovement]

Nah, a nice coat of oil on the rotors makes things a little more fun.

Steve

[vrg3]

Uh, you're supposed to lubricate the portion of the lock pin that goes under the boot, and high-temp grease sounds like about the right stuff.

If a caliper is unable to self-adjust, that's a very big deal. If yours was stuck in a position that kept the outboard pad away from the rotor even when braking, then it makes sense that you wouldn't see brake dust there, since the pad on the outboard side wouldn't actually have been braking.

But if the car stopped without pulling to either side even when that was happening, I don't know...

[NemesisEJ22t]

I should add to vrg3's statement about pulling to either side when stopping with calipers that have stuck sliders. My car didn't pull to one side at all when they were bad, the overall braking performance was just sub par. I would definately try to remove the pads to see whether or not your calipers are stuck.

[ultrasonic]

It finally dawned on me that the excessive brake dust on the passenger side front indicates that the pad is dragging.

So it took it apart last night.

On the pad there is supposed to be (in this order) the friction material, the backing plate, a black shim with slots in it, and finally a shiny chrome looking shim. My outboard pad had TWO of the black slotted shims and the inboard pad had no black slotted shim. That's not right.

I reassembled everything after putting the shims in the right place and cleaning and lubricating the guide pins.

The other problem is that, while the lower piston was able to be pushed back into the caliper, the upper piston may be frozen. I was able to push the lower one in with my hand, but even with a clamp I was only able to slightly move the upper one.

There are some torn rubber boots and plenty of rust. These brakes are going to be replaced in the next week.

Also, I put new set of Falken Ziex 512 in 205/50/16 on. Huge improvement!

[NemesisEJ22t]

You're probably going to notice a decent difference in braking performance from the new calipers, the ones i just put on made a huge difference due to the fact that only one piston on each side was really stopping my car. If your slider pins are in bad shape you should probably replace those as well. Replacments didn't come with the calipers i bought, and the parts store couldn't even order them so i ended up getting them from a Subaru dealer for about $14. Might as well replace everything dealing with the calipers so nothing causes problems later.

[ultrasonic]

You're probably going to notice a decent difference in braking performance from the new calipers, the ones i just put on made a huge difference due to the fact that only one piston on each side was really stopping my car. If your slider pins are in bad shape you should probably replace those as well. Replacments didn't come with the calipers i bought, and the parts store couldn't even order them so i ended up getting them from a Subaru dealer for about $14. Might as well replace everything dealing with the calipers so nothing causes problems later.

Yeah, it's somewhat of a moot point as I have WRX front calipers ready to go. Just waiting for a set of rotors and enough time to make the swap.

[ultrasonic]

WRX fronts installed.

Goes faster. Stops better. All is right with the world.

...well, all is right with my front brakes, anyway.

Next? Exhaust, intercooler, MBC, etc.