Random vibrating brake on 2WD GMC Sierra

2003 GMC sierra 2WD with 155K miles. I get a random issue with brakes. Happens somewhat regular but at unknown times. When I go to brake, pedal vibrates a little and doesn’t feel like it’s going stop the truck. I have checked all 4 brakes and they have over 75% pad left and they are wearing evenly. Plenty of brake fluid in resoiver. I don’t hear any noises when braking. Issue happens daily but not every time. Does not matter if I’m pressing brake pedal easy or braking hard. Any suggestions appreciated.

Did you check the brake rotors for excessive run-out? ( warpage)


Visual inspection of rotors looked good. No groves and no obvious warpage. Other than visual inspection how do you check for warpage?

With a dial indicator.


Are you sure the ABS isn’t kicking in? Mistakenly, that is…

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It could be rust buildup. Does it go away after a while? More noticibale after sitting a few days or a rain event?

Minimal if any rust on brakes, rotors, etc. I’m in the south so rust is minimal. I’ve never noticed it doing it twice in a row or more consecutive. It does it once and won’t do it for a while. Weather does not seem to effect it. Don’t notice it being worse when it rains…and it’s rained a lot here in NC this year.

There may be a way to tell. Sometimes there are small hints. Check the thickness of the pads. If one is thinner than on the other rotor it may be a hint. If one rotor has more rust on the rim, same thing. The best way is to remove the pads and look for a wave. The front ones on my truck looked the worst at first but it was the right rear that was the problem. Upon close inspection, the right rear looked significantly worse for wear and ratty looking surface. They all needed replacement and resurfacing but the right rear was doing the shaking.