I hate brakes....

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If it is pads leaving deposits, does this mean, the pads are cheap, or I should have bed them differently? On my previous set I would brake hard, but keep rolling to let the brakes cool off. On the new set I tried going easy for over the first 500 miles. Both sets have a pulsation.

If it is pad deposits is it likely trying the hard braking may fix the issue?

Thanks!
 
Originally Posted By: Ken2
Has anyone actually measured the warpage of rotors? I didn't think so. The cast iron of the brake rotors does not warp easily. If there is any actual warping, it is most likely to be in a conical shape, not axial run out. Even a new rotor will have some axial run out depending on how true the surface is on the hub where the rotor sits. 0.007" used to be the max standard. Some cars now limit it to 0.003" (three thousandths). I've measured new rotors once when installing them. New SP Performance rotors measured 0.003" runout measured with a dial indicator.

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

"Ceramic" on brake pads means little. There are different amounts of ceramic material in the pads of different makers and different quality lines, and many other materials. What is likely is that the pads that cause the judder are not adequate for the usage of that driver. They may be smooth, clean, problem free for my mother-in-law, and judder like mad for a driver like me.


I agree with this as a experienced tech, and will add a couple of things.. Cleanliness at hub fitment is indeed important - no rust, flatness,etc. - and even tightening ( star pattern ) of the wheel on your new brake job... this can KILL any kinds of rotor/pad combos right from the get-go or after a rotation or whenever a wheel is off !!
Other than those things it's usually a result of rough use/panic stops or undersized brakes being used to the limit.
 
Last edited:
Originally Posted By: actionstan
If it is pads leaving deposits, does this mean, the pads are cheap, or I should have bed them differently? On my previous set I would brake hard, but keep rolling to let the brakes cool off. On the new set I tried going easy for over the first 500 miles. Both sets have a pulsation.

If it is pad deposits is it likely trying the hard braking may fix the issue?

Thanks!


If its deposits, one brand of pad or another might be worse or better. But all pads have friction material held together by binder material in one form or another- its usually the binder material that outgasses. In short, ALL pads will do it to one degree or another.

That said, I'm in no way saying that it CANNOT be runout. Just that very often its not. Runout issues are more common on cars where the rotor is a "hat" that fits over the hub and is retained by the lug nuts... IOW most modern cars. I've never had runout issues in older cars where the rotor is integral with the hub and the inner wheel bearing races are pressed into the center of the rotor. Again, not that its impossible, but with that design another potential source of runout (the hub/rotor interface) is eliminated.
 
Oreilys cheap rotors have a 2 yr warranty I went that route.All the cheap rotors are made in china a couple hard stops or to hit a puddle while hot they are warped.
 
Originally Posted By: cknight49090
Oreilys cheap rotors have a 2 yr warranty I went that route.All the cheap rotors are made in china a couple hard stops or to hit a puddle while hot they are warped.



Please do some research. We all drive in the rain. I have even been to track events in the rain.

Most cars have never had anything 'warped'. Take a good look at a ventilated disc rotor. They simply cannot warp.

Most folks either have runout or pad deposits...
 
Many brake problems can be attributed to installer error.
I advise anyone doing their own brake work to invest in a dial indicator, this is the most important tool for a brake job. Not a power bleeder, piston tool, etc. while all beneficial are not a necessity.

This one is fine for the DIY and will pay dividends many times over.

http://www.tooltopia.com/fowler-72-520-4...id=scsho6812369

A 0-1" micrometer is a good tool have for checking rotor thickness again a cheaper one will work fine. This one is okay.

http://www.amazon.com/Fowler-52-224-001-...+micrometer+0-1

Start by cleaning the hub and back of the rotor where it mates to the hub with a disc, wirewheel, etc.
Use all the lug nuts to secure the rotor using conical washers, tighten them them to spec. Mount the dial indicator.
Check the runout if its more than 0.002" remove the rotor and reposition it and measure again.
Washers..

http://www.brandsport.com/grla-79916.html

If repositioning doesn't correct the runout you need a shim. You can buy them from Napa or RockAuto and other places. Use a full tapered shim not just shim stock in one place.
Using the dial indicator find the high spot and low spot and subtract, this is the shim thickness you need.
Mark the low spot as well as the stud closest to it, remove the rotor and put the shim with its mark pointing to the marked stud.
Put the rotor back, secure it and retest.

Shims

Next check the caliper alignment. This is rare but with reman calipers and reground brackets it happens.
Pump the brakes to close the pads on the rotor.
Using an 0.002" feeler gauge check between the pad face and rotor at the top and bottom of the pad.
If the bottom of the outside pad and the top of the inside pad is more than 0.002" e.g 0.005"
you need to add a shim washer to the bottom caliper bracket between the bracket and knuckle.
Vice versa if it goes the other way using a shim on the top bolt.
You can use shim stock for this job.

If only one pad is out then wither the piston face is off or some rust is preventing proper seating of the pads.
You can usually correct this condition by cleaning or dressing with a file. If its way off and its all clean you probably have a distorted pad backing plate.
 
These China rotors warp like crazy I would feel pulsation after 2 3 oil changes.They are no where as good as OEM unless you pay for high dollar rotors you don't have much choice.I make them honor the warranty I paid 17.00 for 2 year warranty rotors.Even the NAPA select or whatever they are called didn't fair much better.
 
I wonder if I should have been more clear.. I don't think this issue could be run out.. I guess its not impossible, and maybe I mis-understand how runout would cause this. To me.. if a rotor or hub or anything had excessive run out, or was un-aligned it would cause this issue from day 1 of installation.

When.. actually from day one.. the new rotor/brake combo was perfectly smooth.. now after a few 1000 miles.. the pulsation has infested itself.. and is slowly getting worse.. can this still be run out? I don't see how it could be.. to me it would either be a warped rotor or pad deposits..
 
Originally Posted By: Trav
Rotor runout can cause a progressively worsening condition. The high spot will be hotter causing more distortion (most likely solid rotors) and/or increased pad material to be deposited.

Interesting article.

http://www.powerbrake.co.za/tech_info/tech_01_judder.htm


Thanks, I will take a look, is it usually cheaper part store rotors that will have run-out and thickness variation?
 
Originally Posted By: actionstan
I wonder if I should have been more clear.. I don't think this issue could be run out.. I guess its not impossible, and maybe I mis-understand how runout would cause this. To me.. if a rotor or hub or anything had excessive run out, or was un-aligned it would cause this issue from day 1 of installation.

When.. actually from day one.. the new rotor/brake combo was perfectly smooth.. now after a few 1000 miles.. the pulsation has infested itself.. and is slowly getting worse.. can this still be run out? I don't see how it could be.. to me it would either be a warped rotor or pad deposits..


If the runout was ridiculously bad, then you could expect it from day one. But that's not really what happens.

The runout causes the rotor to wear unevenly over time. That leads to thickness variation in the rotor. Then when you brake, the pedal pulsating is caused by the thickness variation in the rotor.

From the Raybestos link I posted before:
Quote:
With excessive run-out, the rotor wobbles as it turns
(Fig.1). Uneven rotor wear occurs when the brake pad
contacts the high side of the rotor causing rotor thickness
variation.Thickness variation causes:
Brake pedal pulsation


Here's an old training video that I found when googling this issue. At 1:10 there's animation that shows you how it causes wear over time, which is why the problem develops over time.
 
Yes thats why i mentioned the micrometer. To check the thickness at different spots around the rotor.
Irregular pad depositing or rotor distortion also happens on some solid rotors that are not very thick to begin with.
The more aggressive the pad the more likely the rotor will be damaged sooner.
 
I remember many years ago, I had to replace rear pads and rotors on a Crown Vic. I was given one premium rotor, and one rotor that had the most pathetic casting marks I had ever seen on a rotor. 1 week later the car cam back with pedal pulsation, so I machined both rotors. I hardly did anything with the premium rotor, but the cheap one was definitely in need of machining, and required multiple passes on the brake rotor lathe.

Don't be so quick to blame China for bad rotors. I often have to replace MOPAR rotors that were made in Canada. On my mom's car, pedal pulsation was terrible, and when I replaced the rear pads and rotors due to wear using Raybestos premium, then the problem wasn't nearly as bad. I have reason to believe the front rotors are also a problem.
 
Never trust the backyard style 'pad slap' special.


Most times if the rotors are within spec, I'll hit them up with the drill and FlexHone brake rotor bit which cleans up the rotor surface nicely. Some new (cheaper) rotors require this out of the box.
While I'm at it, I'll also lube the caliper pins and bleed the brake system for good measure.
 
Originally Posted By: actionstan
Originally Posted By: Trav
Rotor runout can cause a progressively worsening condition. The high spot will be hotter causing more distortion (most likely solid rotors) and/or increased pad material to be deposited.

Interesting article.

http://www.powerbrake.co.za/tech_info/tech_01_judder.htm


Thanks, I will take a look, is it usually cheaper part store rotors that will have run-out and thickness variation?


It can happen to any rotor from the factory, if the rotor is not perfectly flat when ground or turned or will have problems. Machine operator error or machining debris is the usual cause.

Its not just better materials but also better QC that makes the difference. The only way to know for sure if its true on the car is if you use a dial indicator on it.
 
Don't hate brakes because in turn they will hate you back. Simply apply logic to solve your problems instead of throwing new parts at them.

If initially the brakes were nice and smooth, chances are the run out is not a problem, but instead uneven pad deposits are the most likely culprit. There are multiple methods to deal with that and they don’t require new parts most of the time.

If the brakes are pulsating right away or very shortly after the job, I would check out the run out, or see if the pads are properly seated.
There are no guaranteed solutions to these problems, it's all platform specific and, as stated already, more expensive parts may not automatically cure the problems.
 
As-far-as rotors not warping, I have had the best success with BREMBO and Raybestos Pro-Grade rotors.

AAP/WearEver and Wagner Rotors(similar/same rotors) seem to warp soon in all of my vehicles...no exceptions!

JMHO!

CB
 
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