My experience in almost 400,000 miles in 2 HHR LTs has been it's not the rotors.

It has been: bad lower control arm bushings, bad struts, bad shocks and poorly adjusted rear drum brakes.

As I understand, and could be wrong, the rear disc brakes are adjusted by routinely using the ebrake.

 

Lca bushings look good and are intact.How could I test the struts? I use the ebrake everytime the car is parked and I have adjusted it manually. Rear disc.

 

I forgot to add hubs to the list.

If the struts have over about 70,000 miles on them probably worn out. Leaks, bottoming out, odd cupping wear on tires. Same as shocks.

And semi metallic pads eat rotors up.

 

As Donbrew said, I would look at the hubs. If they're not running true, you will destroy a set of rotors with-in 3,000-5,000 miles.

The following articles may be some good tech info for your situation:


Pro-Cut OEM History | Pro-Cut On Car Brake Lathes

Pro Cut Lathe - EBC Brakes

Brake Pulsation Questions, Rotors, DTV

Stop Brake Pulsation Before It Starts, Correct Runout

How To Solve Brake Vibration Permanently - EBC Brakes


By the way, this isn't a commercial for EBC, but all of these links were suggested/referenced by an EBC engineer I was working with.


Thanks,
Ken

 

like donbrew said it may be the LCA, but the rear bushing that i believe is somewhat hidden from view is the culprit. I recently changed my pads and front rotors and it did NOTHING to the brake judder i have. it is all in the LCA's as mine goes. i recently put on a TTR motor mount and to be honest it has helped with the judder too.

 

The only reason I was thinking it's truly brake related is because he said it goes away when he installs pads and rotors (then comes back a few K miles later).

If it weren't brake related, changing the pads and rotors shouldn't fix anything, correct?

 

Each of the things I listed solved my judder for a while.

More questions to pose: Is the PEDAL actually moving? Or the brakes shaking the car? Or the ABS activating?
Many times people say "pedal pulsation" when they really mean "brake pulsation". It is hard for us to tell which over the interwebs.

 

Brake pedal pulsation.From high speed it will shake the car, over 55mph

 

Struts not leaking. no runout on hub bearings.

 

2 different things! Does the pedal physically move? If you checked the runout on the hubs did you check the runout on the rotors?

There are a few long discussions about rotor warp and the "bedding" of pads. Way too many for me to list here. Give the SEARCH a shot, try different search phrases.