Disc Rotor runout question

Chuckman

Chuckman

Well-Known Member
Joined
Oct 9, 2005
Location
Huntersville
Working on my MinLaws Grand cherokee again. She is rough on the brakes. About every 3 months she brings it in with a crazy death wobble from front disc brake rotor warpage- only on deceleration and new rotors clears things right up. Last time she had cracked a front disc clean through and was still able to drive it. It was cracked from the hat radially through to the edge. So I am curious as to what is too much runout? I would like to see what is ok, vs what she keeps having. Its a '02 GC with the 360 I think and she lives in the mountains. I dont think shes a 2 foot driver, but this is crazy to need this much work. If I knew she would keep the truck, I would suggest vented or slotted rotors, but I doubt she will spend the $$. Its cheaper for her to return the lifetime warranty units at my trouble. The pads show no sign of wear. I am wondering if there is an issue in the prop valve, but really dont want to go messing with a stock truck. The dealership isnt doing anything to help remedy the problem - imagine that... But she keeps Newcastles at the house for me when we come up, so all's fair I guess!!:beer:
 
Follow her while she is driving, I'd bet she is riding the brakes.

either that or there is a caliper sticking

Rotors get hot and the pads wil burn in, especially after a hard stop and leaving the pedal down with out moving.

More than once I have pulled rotors to find a nice pad impression on the rotor. THis also causes the pads to leave deposits on the rotors.

That a rotor is actually cracking tells me they are getting WAY too hot.
 
you'll run into a ton of debate over brake lateral runout(and more recent this discussion about rotor wear http://nc4x4.com/forums/showthread.php?t=29721&highlight=warping ), some say .001" some say .010". I have found they pulse after about .001"

I have also found that late model cherokees go thru brakes like none else!

You should be able to tell from driving it if there are caliper or hydraulic problems.
 
3 months!
Wow!
And yeah obvious its getting waaaaay to hot.
Im x2 on either brake dragger or caliper....
 
sha_ba_do_bang said:
you'll run into a ton of debate over brake lateral runout(and more recent this discussion about rotor wear http://nc4x4.com/forums/showthread.php?t=29721&highlight=warping ), some say .001" some say .010". I have found they pulse after about .001"
I have also found that late model cherokees go thru brakes like none else!
You should be able to tell from driving it if there are caliper or hydraulic problems.
Click to expand...

.001 your lathe must be pretty true then, i assume you turn brake rotors, I do and i don't think my lathe is that true and i have never had a problem getting pulsations out with a standard turn. but maybe it is i have never checked it never saw the need, i'll check the next one. But i would think a new rotor would be out a .001 but again never checked.
 
IMHO its probably 80% driver / 20% crappy design/parts... My aunt would wear out pads every 10k and rotors every 2nd/3rd pad change.. She just drove like she was in a race, she didn't speed, just floored it, rode people ass and used the brakes hard, ALL the time...

What is her MPG ? might help determine a pattern or bad habit..
 
yager said:
IMHO its probably 80% driver / 20% crappy design/parts... My aunt would wear out pads every 10k and rotors every 2nd/3rd pad change.. She just drove like she was in a race, she didn't speed, just floored it, rode people ass and used the brakes hard, ALL the time
Click to expand...

Your aunt my arse... THAT'S MY WIFE!

She only has 3 driving states:
- Accelerating wildly
- Slamming on brakes
- Stopped (waiting to repeat the cycle! :shaking: )
 
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