Rumble on moderate braking

As title states, I am experiencing a rumble (think going over rumble strips on the highway) when braking at moderate to hard braking. I think its the pads and took a look at them. They are pitted in the middle but nothing crazy, no metal on metal I can tell. The Rotors do have about 2-3mm of a lip on the outer edge at the most.

Turning the rotors led to a scraping sound that went away after removing pads. This seems a bit of an extreme vibration to be just some pitted pads. I will have to check again but there was no play in the hub as far as I could tell earlier, will check again with wheels mounted for better leverage. The truck drives smooth at above 10 mph and no unusual vibrations or noises on the highway.

Any troubleshooting ideas are welcome. I will update after putting new pads in.

 

Does your steering wheel shake when you hit the brakes?

 

Not that I can tell

 

That tells me is not the rotor.
Might be your wheel bearing.

 

Bad ABS sensor?

 

Do a wheel bearing test. Does your rear view mirror show any vibrations when cruising at freeway speed?

Get the front wheels of the ground and rotate them by hand. Any unusual noise, friction, grinding, etc?

 

So inspecting the driver side there is very little material on the inner side of that rotor. Probably the issue right now. Going to swap rotors, pads and rebuild the calipers. I checked the passenger side where I initially thought the issue was and there was no unusual play and no grinding after removing the pads.

 

Check to make sure your brake caliper pistons are not sticking.

Ah I missed that you are going to rebuild the calipers as well. It's a fun job

 

Planning to, theory right now is that the inner pistons on the driver side or just one piston is sticking. Wore out that pad in a heartbeat (previous owners probably used some cheap pads as well) and ground down the rotor. The headscratcher is there wasn't any abnormal brake noise under any level of braking until 2 days ago. I would expect a pad grinding off almost 3/8 in of rotor would make some noise.

 

Well, the issue was the inner side of the driver's side caliper. Both piston boots on the inner side had lost their clips and were at the tips of the pistons. This left a huge gap letting anything into the calipers. So it basically ground away my pad there to just the backing plate which ground down the rotor to the vanes. I will post pics later of the rotor. The grinding and rumbling was the pad rubbing the vanes. I didn't notice anything until about 4 or 5 days ago. Swapped out the pads, rotors and calipers and it is riding like a dream. Ended up having to bend new hard brake lines that run from the calipers to the soft tubing.