Brake vibration, not rotors.

what about the front brakes?

 

Replace the front rotors or have them machined on an on car lathe.

Under light braking the rear brakes are activated first. This is why you only observe the vibration under heavy braking.

 

Geesh, I was gearing up, then you let the wind out of my sails with that last sentence.

All I can think, is to verify that the piston orientation "stuck", ie: that it was well-seated in the X orientation. The simplest way would be to raise the rear of the car and give the wheels a good push. They should turn a couple of revolutions no problem.

I think what can happen: even if you've got the piston oriented correctly, as soon as you apply parking brake, if rear pad is not solidly seated, the backing plate not locked in, the piston can still manage to rotate, ride up on the pin, and then you'll get drag, and that bevelled pad wear (which you mention).

You really want to hold off applying the parking brake, till after seating the brakes. Pump the brake multiple times before even reconnecting the 12 volt, then maybe a short test drive, then apply/release the parking brake a few times, then the spin the wheel test as a final check.

 

If you have a run out gauge/micrometer you can check the run-out on the discs, start there. I bought a new Durango a few years ago and I had bad braking vibrations in the front wheels. I had it in the shop five times and replaced the disk and hub on the vehicle to no satisfaction and I finally called to ask for a lemon return and they sent an adjuster out and all he did was measure the run out on the brake disk and it was quickly resolved that the spindle was out of spec, not a little but by a lot. Why the dealer could not do that was beyond me. But it may not be your case. YMMV.

 

Depending on the suspension design of the car, it is very possible to feel vibrations but not thru the steering wheel. I just finished a brake job on an Accord yesterday where you can feel the vibration from the front seat but the steering wheel did not shake at all.

Excessive lateral runout will eventually cause disc thickness variation (dtv). DTV is what causes the pulsation, not the runout. DTV can also be caused by pad deposits. For the average person, it is very difficult to accurately measure DTV using over the counter tools.

On a floating caliper setup, you can have a significant amount of runout with zero DTV (then again, it won’t remain that way for long) and the brakes can feel smooth.

 

Rotor runout and thickness spec's, plus the procedure, in the attachment. They mention to mark the rotor and a stud if you remove it, and to reinstall in the same orientation. I probably have screwed that up, didn't do the marking when I removed the rear rotors.

 

o/p says 'not rotors'

 

Maybe wrong though?

 

seems to know his stuff?

 

True. I'm just thinking, if there's a vibration, and the one thing spinning is the rotor, it's the smoking gun?

 

that's where i would start, but i have no idea what i'm doing

 

Did you put in new brake pads also when rotors were replaced?

 

Jack one of the front wheels up so it doesn’t touch the ground, grab the tire at 9 and 3 o clock with palms on treads. Try to tilt then entire wheel back and forth, do this also at 12 & 6 o clock mark. Checking for “play” I think is the word. Then do this for the other front tire

 

Just checking, didn’t see “replaced pads” on original post.

 

Yeah spec (per attachement above) is 0.00197" max (0.05 mm). You can also try taking off the rotor, reinstalling rotated to alternate stud openings.

I'm pretty sure I did that inadvertently on the backs one time, since I had them off and payed no attention to how they were. It was ok.

The shock tower or whatever you call it, directly above, works fine for the magnetic base.