How do I diagnose which set of rotors is warped, front vs rear?
Drive at freeway speed and apply the brakes
Brake pedal kicking = front rotors warped
Whole car shaking = rear rotors warped
Someone here mentioned a while ago – it seems like a good idea but I’ve never tried it – if you think it might be the rear rotors that are warped, do an experiment where you slow or stop the car using only the emergency brake. The emergency brake only works on the rear brakes, so if you get some wobbling or shaking then, it’s a good chance the rear discs are warped.
@GeorgeSanJose
That is a good idea . . . IF the parking brake applies the rear brake pads
If the parking brake applies brake shoes inside the rotor hat, it won’t tell you much
If the vehicle has rear drums, you’ll get your answer
But I believe OP’s car has rear rotors . . .
Yes, rotors on both front and back. I tried the emergency brake trick before posting, but wasn’t sure exactly what to look for. I’ll try again and see if I can tell. Any other tips would be great. Thanks.
If you posted the year/make/model the experts here could tell you whether your car uses the pads-on-disc for the rear emergency brake, or the shoe/rotor-hat technique.
You put a dial indicator on each rotor and then spin the rotor by hand to determine which rotor has excessive run-out.
Tester
This is also the method I use for determining which rotor is warped
However . . . I doubt that OP has a dial indicator
The method I described isn’t rocket science and won’t tell you exactly which rotor is warped (left front versus right front), at least it’ll give you an idea if the problems in the front or the back.
@Randhhand do you happen to have a dial indicator and know how to set it up and use it?
2004 Jeep Grand Cherokee. I do not have a dial indicator, but would. It be opposed to purchasing one and learning how to use it properly.
@Ranchhand
Now that we know what car you have . . .
Your parking brake is a set of brake shoes inside the rear rotor hat
So activating the parking brake won’t answer your question
Use the method I told you about in my first response
Don’t fry the parking brake. There is one more thing to check if the brake pedal isn’t doing anything spectacular. Look at the rotors and pads. If one of them looks really bad compared to the others, that one is probably the worst of the four.
If the rotor is really rough looking and the pads are almost worn out, you found a most likely cause. Fix that one first and see what you have. Hey; if it needs changing anyway…
It is common to find the front rotors warped due to overheating, not very often do I find the rear rotors warped. The city I live in is surronded by mountains and some of my customers warp thier rotors every time they go out of town, I see alot of warped rotors.
In 2006 a class action lawsuit was filed agains Chrysler for WJ (1999-2004 Grand Cherokee) owners for faulty/warped front brake rotors. Chrysler agreed to replace the brake rotors for a one year time period, not a recall.
If the vehicle was parked in my driveway I would purchase front brake rotors before I bothered to take the front wheels off.
@Nevada545 I’ve worked on MANY vehicles with warped rear brakes (drums AND rotors)
It’s possible the vehicles I work on see severe service, since I am a fleet mechanic
I’ve worked on MANY vehicles with warped rear brakes
So have I, what is your point? Don’t you believe the front rotors are 20 times more likely to be warped than the rear? I’ve never seen warped rear rotors on a WJ but I have on alot of Toyota SUVs and the front rotors are always warped as well.
@Nevada545
My point is that warped rear rotors are not nearly as uncommon as some people might believe
I do believe front rotors are more likely to be warped than the rear
I don’t believe they’re 20 times more likely to be warped
That is my opinion, and I believe I’m entitled to it
As I said, perhaps you and I aren’t really working on the same kinds of vehicles
Your customers apparently/possibly drive in the mountains
Mine don’t
I’m not sure what vehicles you work on
I work on all sorts of vehicles, ranging from a Focus all the way up to a Class 8 truck
And, as I said before, perhaps the vehicles I work on see severe service
I’m NOT itching for a fight
I’ve stated what I’ve personally experienced
I’ve stated what I work on
I’ve stated my personal opinions