Vibration when braking especially downhill.

4th gen 4Runner here, 240 k miles.
Had new front brake pads, rotors and calipers installed about a year ago. They also replaced the struts.
A few months ago I started getting some pulsation when breaking from speeds of around 40 mph and higher, so I brought it back to the shop and they replaced the pads and rotors and just charged me the difference in cost ($70) since they were putting “higher quality ones”. A few days later, I started noticing some pulsing again, though not quite as much as before. I brought it back to the shop. They wanted to replace the rear rotors and pads. Instead, the tire shop I went to the day before for some new tires insisted it was better to keep the original rear rotors and just turn them because one side pad was worn 40% more. So I had that done. I’m still feeling a slight vibration, and occasionally I feel the slower pulse indicative of a warped rotor. One time the other day while almost stopped, it was pulling to the left when braking. Yeah, I’m not on any crazy steep hills, and I downshift to help so I know it’s not from bad braking. I don’t know what to to do now. Any ideas of what should be inspected or tests done?

 

The unbalanced braking along with the 40% wear difference (which is a huge amount) points towards possible air entrainment in the line(s). How old is the brake fluid? Did the shop bled the lines when they changed out the brake components? Another possibility if it's not old fluid (moisture absorption), air entrainment or a leak somewhere is to check the anti-lock system (based upon you stating a 'pulsation'). A couple of starting points...

 

Warped rotors... That would be my first check if I felt what you're describing.

Unfortunately some rotors will warp pretty soon if they heat up too fast. I've had this happen on new rotors on a different vehicle. (Powerstop rotors on a sports car) They warped after a few months. Upgraded to DBA rotors afterward. Never warped a rotor again no matter how much I abused them.

If you have a dial gage its an easy thing to check for.



Vibrations can be caused by a ton of different things. But if you're only experiencing it under braking at high speeds and you feel pulsation I'd guess the rotors are warped.

 

thank you. Is it possible to check the rotors for warping with the dial gauge without removing the brakes?

 

Yes. Just have to remove the wheel.
https://www.brakebleeder.com/how-to-measure-rotor-runout/

 

There pins that allow the pads to move within the caliper. If these are warn out or corroded it can cause issues as well.
As someone else mentioned it might be worth bleeding your brakes as well to rule that out. It's an easy enough thing to do.

First ensure all the pads are in fact engaging against the rotor when you apply the brakes.
If they all contact and seem to function properly then check your rotors and be sure that's not the problem.

https://www.youtube.com/watch?v=bbueXKwugNs

 

After re reading your post it sounds like maybe one of your brake pads isn't engaging the against the rotor.

This is what I would do.
Jack up the car, pull the wheels off and have someone sit in the car. Walk around the vehicle and have them hit the brakes while you spin each rotor individually. This will allow you to see if the pads (both sides) are engaging against the rotor.

Bleed the brakes and do this test again.

If the pads (both sides) don't engage against the rotor pull the pins and clean them up with a wire wheel or sand paper. Now you can do the same test to see if the pads contact the rotor when you apply the brakes.