Came across this article while looking up some info on warped rotors.

There's no such thing as 'warped' brake rotors - Orlando Autos | Examiner.com

Which lead me to this.

-Warped- Brake Disc and Other Myths

I was wondering what everybody's though's are on this. I was starting to get some steering wheel vibration while braking around 40-45mph and only around that speed and its intermittient usually only when its warm/hot out. My initial thought was "crap my rotors are warped" but now reading this article i'm wondering if its something else.

I have a 6mt with almost 50k miles and have usually followed the "tip" stated by the first article of staying off the brakes after the car has come to a complete stop when do heavy braking (freeway exiting mainly). Still on the original squeaky in reverse OEM pads (replacing soon with stoptechs or hawks) and OEM rotors (considering replacing with some slotted if it is time). I went to big o tires over the weekend to have them check my run-out and they said it was within spec. And that my rotors and pads still had some life in them. Considering going to another mechanic to have them look at the run-out also as a second opinion.

 

This is more or less how I feel about it. I think 99% of brake shimmying is either caused by a damaged suspension component, or as you said, uneven transfer of brake pad material. However, I think that resurfacing a rotor DOES help in that it completely grinds off the surface of transferred pad material. They're literally machining off the surface of a rotor, the same way that sharpening a knife removes the top layers of metal. Unless the brake pad material is chemically altering the metal of the rotors, machining SHOULD get rid of the surface inconsistencies.

 

The articles you linked are correct, brake rotors do not typically warp. The pulsation under braking is form pad deposits that are left unevenly on the rotor surface.

Pro Tip: please spell "brakes" correctly form here on out when you are describing the part of your car used to stop (not "breaks") or you may cause a number of our members' heads to explode when reading your posts or cause people who can give you helpful information to completely ignore your posts because it's so maddening to some people.

 

haha wow... shows how much i spell check -_-... fixed...

Thanks Black Betty and GoFightNguyen... I can always expect to see you on any post as some of the first responders.

 

There are 2 things that may cause brake vibrations:
1. Runout - Measures how much the rotor's braking surfaces move laterally as the rotor spins. Measured with a dial gauge.
2. Thickness variation - The variation in thickness of the rotor at 8 or more points on the rotor. Equally space the 8 points and measure the thickness with calipers, then compute the difference between the min and max.

Did the shop check for thickness variation?

 

Rotors do indeed warp, and also accumulate pad material. I agree that not leaving your foot on the brakes after hard stops helps prevent the pad material accumulation but on good rotors it should be able to be burned off with a series of hard braking without full stops. Resurfacing just removes precious metal making it more difficult for the rotors to absorb and shed heat. Which is why brake vibration usually occurs even quicker after resurfacing. Like all metals there is good and bad stock rotors are made of. My theory is that cheap rotors are made from cheap, less refined metals making them more prone to uneven expansion when heated and lower overall tolerance to heat and heat cycling. I just bought my fourth set of frozen rotors, the first for my 2012 g37 whose stock front rotors are trashed at 22K. I have had three sets of frozen rotors (and Hawk pads) on my Dodge Dakota and they have all lasted over 65k miles with no vibration ever. Those miles included a lot of towing also. They are cryogenically frozen to realign the molecular structure in the metal. It makes them much more heat tolerant and even in their expansion when heated. They are pricey but what you pay for up front more than pays you back in the long run. I bought the slotted rotors for my g, I've had incredible results with them on my truck, particularly when stopping the truck and boat trailer.

 

Yes it takes off precious metals but if you properly bed your brakes you wont have this issue with new nor turned rotors.


To all: Please research properly bedding brakes.

 

He did measure the thickness but only from the "top" side of the rotor did not go around it... nor did he give me the numbers... just said they were still ok and I was in a rush to leave so i just took it for what it is... I'll go back and ask them do run-out and the correct thickness variation testing.

for those reading this and don't know what Tazicon is talking about here is a link to a brake bedding procedure:

https://www.myg37.com/forums/brakes-...and-video.html

 

Rotors DO warp.

I have had hundreds, if not thousands of rotors on a lathe, and measured the runout, its proof!!!

Not to take away from deposits also causing brake pulsations.

 

Lol. Right after the "spell correctly" too.

Sorry, had to BB.