Rear Brake Rotor feels warped sometimes?

[Dagwood]

Ok ...this one has me baffled. The vehicle is a 2003 Toyota 4runner. Disk brakes on all wheels. I replaced the rear rotors and pads because I perceived a throbbing in the Pedal and it sure felt like a rear brake rotor was warped. Now, with new rotors and pads I have noticed that when I stop hard...it is very smooth. I stop gradually it is also very smooth...but if I stop with medium brake peddle pressure there is a throbbing in the peddle. It feels like a warped rotor...but I am not convinced. Any suggestions?

 

[Dagwood]

Ooops...this is the wrong place for this topic. Sorry...I reposted under Mechanical/Maintenance Problems tips and tricks

 

[Big Jim]

I would not have seen your post there.

You may have a sticky caliper. Most likely the caliper slide pins. Did you remove the slide pins and check them for wear and properly lube them when you did the brake work? Less likely but possible is a stuck caliper piston.

You may also have improperly torqued lug nuts.

 

[labman]

Big Jim has an extremely good point about the hardware. The caliper must slide back and forth freely for disk brakes to work the way they should. Good point on torquing the lug nuts too.

Three years is a little too soon for a stuck piston even in the salty North unless you have a damaged boot.

I mistook tire problems on my Cavalier for warped rotors. Once I dumped the OEM Goodyears, my problems went away. Rotate the tires and see if the problem moves to the front.

 

[unDummy]

When stepping on the pedal, you can NOT feel which rotor is bad. You'll need to measure them all for thickness and runout.

If it isn't the tires, don't be surprised that it could be your front rotors.

There isn't much work done by the rear brakes of most vehicles. But, all it takes is someone to forget to release the parking brake .... and 'toast'!
I also had one issue with air in front calipers causing more rear bias.
A defective master could also be an issue.

Some vehicles are also sensitive to wheel lug nut torque causing gradual rotor/hub/rim issues.

I'm also assuming that the rear brake work was 'competent' using quality parts. Cheap parts(and some OEMs) can lead quickly to future problems. Competent means that everything was bled, lubed, inspected, checked, replaced, adjusted, cleaned, torqued......

I would consider turning/cutting/machining all four rotors, reusing all brake components(hit the pads with some sandpaper), perform a good 4 wheel bleed, and see if problem immediately goes away.

 

[Dagwood]

Thanks for the advice. I have not changed the brake fluid and I still have the OEM rotors. I should have them turned and see it that helps.