Imbalance issue

[mikeb21]

1999 GT daily driver over 220k miles and have changed the calipers etc many times over the years due to PBR calipers sricking but never had the issue I face.

Hadn't used car for a while due to holidays etc and drove ~100 mile drive for work and was violently pulling to left when braking. Assumed sticking caliper so that night stripped and found pads on left almost non existent whereas right still had meat on them. Testing it seemed the right caliper wasn't moving efficiently leaving left to do all the work.

Had a full set of calipers pads and rotors stored ready to fit so fitted them and bled system. Initial testing seemed OK.

This last week have covered over 400 miles for work and its still pulling to left with hard braking. It seems a little inconsistent as don't notice every time I brake hard but its there.

Tried bleeding again but still same. Tested with hard braking on deserted road and could feel it catch on left pull then right would catch and things are straight.

Things to note....car is drifting to left a little so alignment does need looking at. There is some slight vibration through steering wheel at times.

Concerned there is something causing an imbalance that makes left caliper lock first and it was doing this for a while that perhaps i had not noticed hence original left pads were so heavily used?

Any ideas or suggestions?

 

[Mustang5L5]

Two things would come to mind here. Either the pistons are in fact sticking again, or the caliper slide pins themselves are seized in the bracket. The latter usually causes uneven pad wear as well.

PBR's are very prone to sticking with the car sits for a long period of time, especially with old brake fluid. I've even seen remans stick right out of the box.

My own car sat for a year and both front calipers were stuck. I just went to cobra brakes. $50ish for the rotors each, and a set of cobra calipers and pads. Reused the original brake lines because they were the same on 99-04 cars. Just needed a banjo bolt. No more worrying about sticking calipers and car looks better and stops better.

 

[ttocs]

Years ago I had a ranger that developed a vibration when I was on the brakes. It started very slowly and eventually got bad enough that it would pull the wheel to one side. When we took it in they found that the wheel on that side had developed a bubble in it where the steel belts separated and under normal driving it wasn't bad enough to notice but when the front end had weight on it then you could easily feel it.

 

[mikeb21]

Two things would come to mind here. Either the pistons are in fact sticking again, or the caliper slide pins themselves are seized in the bracket. The latter usually causes uneven pad wear as well.

PBR's are very prone to sticking with the car sits for a long period of time, especially with old brake fluid. I've even seen remans stick right out of the box.

I know the situation with PBRs well, having owned the car for nearly 20 years and covered over 160k miles I've had many instances of sticky/seized PBR Calipers or Caliper Pins.

That was my suspicion when the car was violently pulling to the left *every* time I braked. I stripped the car and could see from testing the left caliper was working efficiently both pistons moving freely, whereas the right had a "sluggish" piston (e.g. only one was moving properly).

Hence I completely replaced the calipers, rotors and pads with new ones (reconditioned) that had been sat on my shelves for a couple of years.

The left pull is no longer violent and consistent every time I brake, but still there under heavy braking despite replacing calipers, rotors and pads.

Its possible that one of the new calipers is also sticking "right out of the box" but a strange co-incidence its the same side!

 

[Mustang5L5]

I know it's a coincidence, but give the horrible rep of these calipers i wouldn't rule it out.

The other thing to look at is the control arms. How are the bushings? If they are failing and moving, it could account for some of the drifting you are seeing. How are the tie rod ends? Loose suspension components can also manifest into steering wheel vibrations as well. I had a car with a bad bushing in the control arm, and it would violently shake the steering wheel under moderate to hard braking.