In just the last week or two I have noticed that under hard braking a rough, grinding noise occurs, (similar to the sound of the ABS kicking in), but only on the drivers side (no vibration in the pedel too)

I installed 199mm Tundra calipers along with new pads and rotors less then 5k miles ago so I know it's not the pads.

The problems seems to stem more from the sudden shift of weigh towards the front of the car, caused by the harder braking, than from the braking itself.

Any ideas?

Check the caliper mounting bolts. If they backed out at all they'll cause problems.

I had a sort of grinding noise going on and I swapped out the cheap-o duralast semi-metallic pads I had to ceramics and the problem was gone... I also re-lubed the caliper slides in the process.

Maybe your tire is rubbing on something when the front suspension squats down under braking. Possibly a part of the fender liner that got bent toward the tire or something?

My first thought was the wear indicators on the pads, but you say they are new pads/rotors, so

Well I'm back from diagnosis with an answer and a picture


Short Story: Inside of the wheel was grinding on the caliper, or rather, the caliper was grinding down the surface of the wheel.



Long Story: Turns out the casting of one of my wheels is different than than the casting of the other three. Three wheels have an area already ground out from the factory where the caliper was hitting the inside of the wheel. When I installed the Tundra brake Mod a few months back the current front wheels had the clearance not to rub the caliper. I just had my wheels rotated last week and that is when the problem arose. So the wheel that didn't have enough clearance must have been just rubbing the whole time lightly, and more so under hard braking. Most of the necessary grind of the wheel is done now...so I guess I'll just have to take off another millimeter with a grinding wheel later on. For now I just rotated the rear and front tire on the drivers side to fix the problem.

D'OH! Can't believe I didn't think of that.

That doesn't seem like something that would change w/braking pressure though. Which begs the question: which component in the equation is moving? The caliper, or your hub/wheel mounting surface?

Yeah that is causing me to wonder what might be moving too...

Normal play in the wheel bearing would be enough.

That's what I was thinking too, mainly because @ 250K miles (assuming they are original) they probably have a bit more than "normal" play in them.

I think they are probably original. Good points fellas. Thanks for the input.

thermal dynamics too... when under breaking the caliper would be heating up, possibly enough to cause it to come in greater contact with the wheel...? just a thought, i know its kinda hard to think there would be that much expansion but who knows...