"Warped rotors" - Let's have a discussion

[dross99_si]

Now first I just want to say that this thread is meant to be a friendly discussion.
I understand that everyone has their routines and habits when it comes to servicing their brakes and people should do what makes them comfortable and spend their money how they wish.
I also understand that Tahoes/Yukons aren't race cars here, but being a part of the EVO community has opened my eyes to the notion of warped rotors. I've read countless discussions between many members of the community that routinely participate in competitive HPDE and time attack events. The general consensus among these guys is that uneven pad material transfer on a rotor is what causes the rotor to seem warped (aka runout) and rather than having their rotors turned/cut, they remedy this by going through the proper procedure of either rebedding their current brake pads or bed-in a new set of pads. Some even lightly sand the surface of the rotor first to remove the old layer of pad material to make the bedding process quicker/easier. We are talking 30 minute sessions of repeated high speed and heavy duty braking on a racetrack conditions here. Conditions our trucks will never see.
The majority of these track junkies swear that there is no need to ever have rotors cut.
I found this whole subject very interesting and figured I'd share this info and have a discussion about it, as I see so many posts on this forum about people replacing rotors or having their rotors turned just because they are changing pads or believe the rotors may be "warped".
Now if your rotors have deep grooves, lips, cracks or otherwise obviously severely damaged then replacing may be your only option. Having them turned just because you are changing pads or feel a shudder, shimmy or vibration just MAY be unnecessary...
Many of you guys may be well aware of all this stuff. Some may not be.
All I'm **** here is sharing some information.

Here are a few articles that are very interesting:

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

http://www.brakeandfrontend.com/warped-rotors-myth/

http://www.mossmotors.com/SiteGraphics/Pages/brake_discs.html

Basic bedding procedure:

http://brakeperformance.com/bedding-in-rotors.php

http://www.stoptech.com/technical-s...ions-and-procedures/stock-brake-system-bed-in

http://www.wilwood.com/TechTip/TechPadBedTip.aspx

 

[drakon543]

Ill read through your links sometime later but i do have some thoughts if everyone can keep this thread peaceful. If a warped rotor is generally just caused by pad material that has transfered onto a rotor shouldn't just cutting off the high spot be quicker and easier. Im convinced places that cut rotors intentionally take off too much anyway just to try and make sure you will be back. Instead of just cutting the whole rotor they should just be looking for a high spot and cutting it off. I haven't tried cutting a rotor at work yet but ive cut a few other things on our lathe in a similar fashion. Anyway i just don't have warped rotor issues anymore haven't had that problem in at min 5 years. Not since i finally got my wife to ditch this pos 98 ****** wagon she had.

 

[dross99_si]

I personally haven't had rotor isues on any of the vehicles I've ever owned either.
Don't see why the thread wouldn't stay peaceful. Just friendly discussion.

 

[08HoeCD]

Glad to see this thread and the content provided thus far.

I'm experiencing significant shudder/vibration during about 40% of my braking, typically when braking from higher speeds. What's interesting in my case is that I had front brake work done less than 60 days ago, and I really do not have occasions to brake heavily, or not enough to cause what I would believe to be a warped rotor scenario.

Long story short, I decided with the shop to have them resurface both front rotors and install new pads, and the new pads are moderate quality at best. I know: not the best scenario. Braking seemed fine for a few days after, but the shuddering returned within a few weeks.

I have not officially bedded-in the brakes and feel that I have little to lose to try the procedure and gauge results.

 

[mizzouguy]

I used to work at an O'Reillys, and turning brake rotors was one of my duties. One interesting thing to note was how much warp was actually in most of the rotors that I turned. Now I cant speak for the service history of said rotors, but I know that when i put them on the lathe, first by cleaning the mating surfaces and seating them properly to the aligning cups, once you turn on the machine and it starts to spin you can see a measurable amount of unevenness. Sometimes the inside edge of the rotor would be thinner, sometimes the outside edge would be thinner, sometimes you would start to cut and the blade would miss half the rotor as it turned. I think a lot of this depends on correct caliper operation and brake pad type, but still. We had a spec book produced by Wagner that listed a runnout limit for every application and if it was below this "safe" limit, we would not turn them and suggested replacement. Maybe a sales, gimmick, but seemed like good info. Our goal was a smooth, even surface across the entire contact surface of the rotor while taking the minimum amount of metal off to make that happen.

 

[Kpwweb]

Seems like a good amount of rotor warpage is caused by not properly tightening lug nuts. I have seen too many "mechanics" go around in a circle with an impact and call it good. Some use sticks, others don't. Put a few thermal cycles on it and brake stresses and you get warpage.

This always seemed reasonable as I always use a torque wrench criss-cross and never (knock on wood) had problems with warpage. With many different cars (and driving styles!) and brakes.

I also thought this was why high-performance brakes had different hats--aka two-piece rotors.

 

[Erik G]

first - every pad manufacturer has their own bed in procedure. Read it and do it. Some do not want a hard bed in, and some do

I've seen rotors with bad runout right out of the box. Don't buy cheap parts

If your rotors are warped, you will feel it and should hear it at low speeds even without breaking. It will feel like a bad balance

 

[Gurrzt]

A lot of the time "warped rotors" are caused by incorrect wheel torque technics, that is not torqueing down the lugs in the proper pattern, or over torqueing the lug nuts on the initial installation of the wheel.

 

[Ex Euro Driver]

Any type of uneven rotor surface (warping or pad material transfer) can be exacerbated by worn front end parts as well. As these heavy trucks age, the feel of pulsing in the steering wheel gets worse and worse. I've got some pulsing in the front end mainly at high speed braking. It's not all the time but imagine it's made worse by loosening parts with 56,000 miles on them.

 

[dross99_si]

All great input so far. Thanks for contributing guys!