ORB

I have been experience some violent vibration when braking at speeds around 40-50 mph. After some searching, It seemed like it would be the rotors had warped, but today I removed my wheel and checked out the rotor very closely. It looked fine and perfectly flat. The brake pads also seem to have a lot left. Now I have no clue as to what could be causing the vibration during braking. Could the rotors be warped and I just don't see it? Any other ideas?

jimbo74

you probably cannot see if the rotor is warped unless it is really bad... the level your eye corrects to focus can easily hide the out of true

ORB

The vibration was pretty violent (the whole truck was shaking). If it was warped so little would it still feel so bad. Basically I'm wondering if I should "bet" on the rotors being warped and risk $140...

jimbo74

waht rotors are you buying?! a lot of things can cuase vibration, i would do mroe searching first, rotate the tires see if the vibration improves.... does it only vibrate when braking at speed? or all the time? other times more violent then others?

fadetoblack72

Also try slowly applying pressure to the e brake to see if it might be the back brakes.

DMG

There is no way to see if a rotor is warped visually. Some develop thick spots from heat, some warp when very hot and aren't too bad cold. If you have a dial indicator you can check runout. Anything over .004 you will probably feel because toy calipers don't flex much.

My99

It's your rotors. As the guy above said, you won't be able to see it visually. You can go have them turned and see if they can take care of it. If not, new rotors.

MTL_4runner

There is no way to see warping visually on a rotor unless you spin it as a decent speed on the truck (very dangerous, don't try it!). Take it in and have it turned or better yet, if they are warped, get new ones.

firemedic

It's your rotors, you can't see it visually. You will be much happier with new rotors!

Bennito

You won't be able to see if your rotor is warped. However, if you do some googling on warped rotors, you'll find a strong contingent of people saying that rotors never warp. THey say the uneven braking is due to deposits on the rotor (I don't remember that may influence uneven rotor wear).

I'd suggest first adjusting the rear brakes then going through a bed-in procedure (allegedly the hard braking and high heat can get rid of deposits). Then wait for the brakes to cool and see if your problem is solved (may be and no tools were used). If you've still got brake shudder/judder/whatever I'd then pull the wheels and visually check for deposits on the rotor. If you can, remove these yourself (I've used brake cleaner, green pads and really fine sandpaper - i"d google for more info on this. Of course getting your rotors turned will remove the outer metal on the rotor guarenteeing a nice clean braking surface). Now that both sides of both rotors are clean and shiny, I'd go through a bed-in procedure. If you still have brake shudder then worry about buying new parts or paying to have your rotors turned.

Obviously this advice is worth what you paid for it. The upside is that the first two steps are nearly free and may solve your problem.

And yes, I'm notoriously cheap.

Ironmike4x4

Usually you cannot see a warped rotor, we use a dial indicator for it. Does the steering wheel shake when you apply the brakes? Do you apply the brakes firmly and slowly or just slam them on at the last minute? Maybe like someone said to rotate tires and see if that helps. To see if the rear drums are maybe not right, you can drive a ways and apply the e-brakes (not on some hwy at 60mph!) and see if the shaking only occurs then, if it does then it's the rears.

PirateFins

Poor mans dial indicator.
Take a nail, touch it just barely to the rotor surface in a spot where you can tape it in place (like on the caliper). Rotate the rotor 360* and watch what the nail does. If it touches just barely all the way around you are fine. If it digs in at certain places or the rotor surface moves away leaving a gap it is warped. Depending on the amount of space or diging in that is created, is the level of flatness. (Note: They will not be truly flat to begin with, but you will be able to see just how non-flat they are). Do this to the inside and out side of each rotor.

Have you checked to see if there is any play in your wheel bearings? This can also exhibit signs of warped rotors if they are not tight to spec.

ORB

Thanks for all the replies!!

Sounds like a overwhelming yes on the rotors being warped (or having deposits). Just as a real quick check of the rear brakes, so would I drive at speeds 25-50 or so and use the e-brake to stop? Looking at the rotors, would deposits look like little blemishes in the polish of the rotor?

Thanks again guys

Bennito

A/S/L?



Errrr, I mean what year is your vehicle and is it a truck or 4runner?

ORB

1999 4Runner Limited

Bennito

I have no idea how to test your rear drums for being out of round or whatever else may be wrong.

Blemishes i've seen have been obvious. dark spots on a polished rotor.



For adjustment:

Either search for brake adjustment (long thread started by bama chem, i believe) or take the below with a grain of salt (again there's a lot of info in that thread - the below worked for me but its only one person's experience).

Find a barren road with a slight incline. Drive up to the top and put the car in neutral. Let off the brake. Every ten feet stop via the emergency brake. You're looking for the handle to only come up about 6-8 clicks. If you haven't done this before you may want to be careful the first few times as your handle might reach end of range and not be engaged enough to stop your truck. Repeat until you're stopping with the prescribed 6-8 clicks. This may require 50-100 stops (so don't get discouraged after 5 or 10).

ORB

Yeah I've read that thread.