Brakes 20m miles, car shudders/pulses when braking

Djmech26 · July 20, 2024

2019 sierra SLT. Just looking for a little advice before I drop money into a diagnostic check. Front brakes have 20k miles on them, rear about 25k. I just recently noticed the car shuddering/pulsing when braking, and a small squeal at very low speeds when I’m about to come to a stop and applying the brakes (such as driving though a parking lot slow speed and braking). Dealership thought it could be a sticking caliper, but they said pads are wearing good and would need a few hours to look further into it. Does this sound like a caliper issue, or does it seem like more of a rotor warping issue?

garagerog · July 20, 2024

Could be either. What's the history on the rotors? Did you replace with new rotors with the pads when the brake job was done or just have the original rotors turned? And brand on the new rotors if replaced as well as the pads. OEM, quality aftermarket or cheapos?

Djmech26 · July 20, 2024

Both rotors and pads replaced, done by a GM dealership.

garagerog · July 20, 2024

5 minutes ago, Djmech26 said:

Both rotors and pads replaced, done by a GM dealership.

Back in the 1990's I had a Cadillac dealer do a brake job on the wife's Sedan deVille. While looking over the bill I noticed that they had charged me for turning brand new rotors. When I questioned this I was told that it was less expensive to the customer for them to use the less expensive aftermarket rotors available and turn them to make sure they were true than to use the OEM Cadillac rotors. I was kinda shocked by this on two fronts, that the dealer didn't ask me which way I wanted to proceed and secondly that GM allowed the dealer to use aftermarket parts when factory were available. I'm guessing that GM has cracked down on this and you won't see this practice any more. In any case, the brakes were fine after the brake job.

Djmech26 · July 20, 2024

Would there be any issues with replacing pads and rotors first, and then if issue remains doing the calipers?

Gangly · July 25, 2024

This is simply a warped rotor, possibly from excessive breaking, hard braking or driving with 2 feet, or defective rotor. When a caliper sticks, 99% of the time one pad will be severely worn while the opposite pad is not. You have even wear so its not a caliper issue and no need to replace them. Buy new rotors, or get your existing rotors "turned", and be done. Warped rotors do not cause pads to go bad, so no need to replace the pads unless they are below the wear indicators.

Edited July 25, 2024 by Gangly

Djmech26 · July 25, 2024

I appreciate the info, so this accounts for all symptoms (shuddering/pulsing, slow speed squeal)?

Is there any benefit to getting drilled and/or slotted rotors to minimize heat? There are aftermarket as well as ACdelco gold line that offer these options. I guess I may brake a little hard but never had a warped rotor in any vehicle I’ve owned.

Gangly · July 25, 2024

A warped rotor is the direct cause for shuddering/pulsing when you apply the brakes. When you apply the brakes while having warped rotors, the warped (wavy) surface results in the brake pad application rapidly transitioning between normal, then hard, then normal, then hard, then normal, then hard, (repeat) at a very high frequency, regardless of your foot application, and gives a pulsing and shuddering feel. Imagine being on a boat in big waves vs a smooth water surface. Braking and accelerating across a smooth surface is very linear, but if you try to do the same thing across rough water, you will constantly be slowed every time you ran into a wave, or tried cresting a wave. Its the same with the brake pads sliding across the brake rotors. With a warped (wavy) rotor, the pad is effectively reacting like a boat going across a rough surface, constantly being slowed down every time it hits a wave, which in turn creates a pulsating feel because of the non-linear rate braking.

I have 130k miles on the original pads, rotors, calipers, etc. and I have zero issues. I believe the factory brakes to be more than adequate for my needs, but then again I don't tow heavy loads with this truck often so I cant speak about that. 90% of my miles are highway miles, and the brakes have been excellent.

Djmech26 · July 25, 2024

That all makes sense, and I guess could contribute to the squealing as well. What I’m curious about now is if the dealer who replaced these would replace these under a warranty. They only have 20k miles and it’s only been a year. The kicker is I purchased this truck off my friend, so I’m not the owner at the time they were replaced. I’d think parts should follow the car not the owner…..

Gangly · July 26, 2024

17 hours ago, Djmech26 said:

That all makes sense, and I guess could contribute to the squealing as well. What I’m curious about now is if the dealer who replaced these would replace these under a warranty. They only have 20k miles and it’s only been a year. The kicker is I purchased this truck off my friend, so I’m not the owner at the time they were replaced. I’d think parts should follow the car not the owner…..

I would think it should, but I really don't know, and I never put my faith in a dealerships hands when it comes to them taking an "out of pocket" hit. Good luck to you, I hope it ends well.