Shimmy mystery

[KennyRedline]

Hey guys, I joined this forum because I have no idea how to solve this problem. My g/f's 2003 4-Runner (V-6) has a vibration when braking. She has gone and had the brakes done 3 times now, the last time was new front calipers, rotors, pads, the works. The vehicle drives fine for about 10,000 mi, then the shimmy starts to come back. She has two sets of wheels, winter and summer, the shimmy is there with both sets, and it started on the summer set that she only bought last summer. She does mostly highway driving, there is no vibration when she is driving, only during braking, and like I said, everything has been replaced. The shimmy is speed-relative, it decreases as the speed does.
Any thoughts?
Thanks!

 

[drewm]

There's only a few things that could cause that.

First is the shop torquing the wheel lugs without using a torque wrench? Torquing the lugs unevenly can cause uneven rotor wear which causes rotor warpage.

Second, driving style can cause warped rotors. Is the driver riding the brakes, or using them significantly and then the vehicle goes through water? How long do the brake pads usually last? Calipers can warp if they are hot and then you get water on them which causes them to cool and shrink unevenly and warp.

I'm guessing it has to be one of those two things, there's not much else that could cause it.

 

[KennyRedline]

There's only a few things that could cause that.

First is the shop torquing the wheel lugs without using a torque wrench? Torquing the lugs unevenly can cause uneven rotor wear which causes rotor warpage.

Second, driving style can cause warped rotors. Is the driver riding the brakes, or using them significantly and then the vehicle goes through water? How long do the brake pads usually last? Calipers can warp if they are hot and then you get water on them which causes them to cool and shrink unevenly and warp.

I'm guessing it has to be one of those two things, there's not much else that could cause it.

No, the vehicle doesn't do any off-roading, just highway. We took it to the last place that put new front rotors, pads and calipers, all that was still under warranty. He suggested it might be the rear brakes not working properly, making the front brakes do that much more work, overheating and warping the rotors. He's going to check it next week.

 

[drewm]

No, the vehicle doesn't do any off-roading, just highway. We took it to the last place that put new front rotors, pads and calipers, all that was still under warranty. He suggested it might be the rear brakes not working properly, making the front brakes do that much more work, overheating and warping the rotors. He's going to check it next week.

Rear brakes do almost nothing, I'm pretty sure it's not that.

Honestly, it's REALLY hard to overheat and warp the 4runner brakes because they are 4 piston calipers with vaned rotors which are one of the best brake setups short of racing brakes.

Offroading will never warp rotors, you're going too slow for that to happen. How long are pads lasting? If the pads aren't lasting very long (under 30k miles), then the driver is overusing the brakes. Does the driver ride the brakes? Riding or overusing the brakes will cause rotors to overheat and warp. Make sure it's not the driver.