Warped Rotor debate

[Aaron]

My post in V8 Beast's thread sparked some opinions on this that differed from my own.

 

My statement: Warped rotors are caused by pad material being fused to the rotor causing an uneven rotor surface. This causes the pedal to pulsate. This is commonly referred to as a warped rotor.

 

Their statement: A warped rotor is the disk metal itself bending from excess heat.

 

My evidence: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

 

Discuss

[SinisterSS]

I'm going from the the 3 years of school I have, the Acura Tech Line people (who are engineers and designers) the 13 years of Acura school I have, 15 years of experience, ASE certified, oh and the fact I do brake work almost everyday, so I'll take all that over some stoptech site who probably only researches their product and nothing else, with that being said, go drive your car about 45mph with one foot on the brake creating excessive heat for 3-4miles then tell me your "pads" caused that and not the heat. all of us who are telling you are wrong are guys who have or still work in the field, I highly doubt you have any automotive technical repair skills, other than what some web site tells you

[Doug1647545489]

Interesting article.

[nurkvinny]

There really isn't any debate to be had. If you had said, "brake material can cause havoc on rotors", I would have agreed.

 

But, to say, "rotors don't bend from getting too hot" is 100% wrong.

 

Sorry.

 

EDIT: I guess I'll throw my sources out too... ASE books and working as a mechanic for 10 years at a family shop where my Dad performed 10,000's of break jobs and I performed 500+.

 

And after you have personally watched a couple hundred warped rotors spinning on a lathe, there is little doubt that the rotors themselves are warping.

[Aaron]

I'm going from the the 3 years of school I have, the Acura Tech Line people (who are engineers and designers) the 13 years of Acura school I have, 15 years of experience, ASE certified, oh and the fact I do brake work almost everyday, so I'll take all that over some stoptech site who probably only researches their product and nothing else, with that being said, go drive your car about 45mph with one foot on the brake creating excessive heat for 3-4miles then tell me your "pads" caused that and not the heat. all of us who are telling you are wrong are guys who have or still work in the field, I highly doubt you have any automotive technical repair skills, other than what some web site tells you

 

Heat causes the pad to essentially melt onto the rotor.

 

Decades of racing evidence>your exprerience

 

And no need to be a douche about it. Its a discussion.

[Aaron]

There really isn't any debate to be had. If you had said, "brake material can cause havoc on rotors", I would have agreed.

 

But, to say, "rotors don't bend from getting too hot" is 100% wrong.

 

Sorry.

 

EDIT: I guess I'll throw my sources out too... ASE books and working as a mechanic for 10 years at a family shop where my Dad performed 10,000's of break jobs and I performed 500+.

 

And after you have personally watched a couple hundred warped rotors spinning on a lathe, there is little doubt that the rotors themselves are warping.

 

So what is the explanation of the stoptech article then?

 

There are dozens of sites that support this, but stoptech is the most recognizable.

[Dave1647545494]

rotors warp for sure I've had them do it right out of the box

[Aaron]

pad material fused onto the rotor is indeed metal. It is just a different composition. It will still look warped, but be from the pad material, and not the actual rotor metal.

[Dave1647545494]

there is nothing wrong with the article pad material can unevenly deposit on a rotr and cause a vibration but other things like rapid cooling improper wheel torque and over heating can cause the metal to physically change

[Aaron]

I understand there are 2 sides to this.

 

Yes they warp.

 

No its the pads.

 

Saying that they warp, you have seen it, is not valid. Please explain with detail how you know the composition of the warped rotors high or low spots. The article does this with clarity. The posts that say, yes they warp, I have seen it, are bogus.

 

Again, this is a discussion. I am willing to be swayed with evidence. I have no stake in the outcome of this, so lets keep it civil.

[rl]

Slap a dial indicator on the endge of a warped rotor where the bad DOESNT contact, it will show runout. Metal warps from heat.

[Aaron]

Pulled from a forum from user curtis73:

 

Yes rotors warp, but they do not cause the pulsating brakes everyone complains about. That is from cementite inclusions in the cast iron.

 

http://www.stoptech.com/tech_info/w...brakedisk.shtml

 

I've personally confirmed their claims with a scanning electron microscope. Perks of being a BioChem major back in college.

 

If you think about it, calipers (floating and fixed) are designed to put equal pressure on both sides of the rotor. If the rotor is warped, either the caliper moves (floating caliper) or the caliper transfers fluid. Even if it didn't, when the warped part comes around, it would add friction to one side and remove it from the other, keeping mean friction similar throughout the rotation.

 

machining rotors removes cementite inclusions, but if you don't properly bed in new pads, you'll be back at square one in a week or less. Its happened to me many times with my track pads. within a week there was little or no runout, but the pulsing was unbearable. I've also had rotors with lots of runout and no pulsing at all.

 

I think I see a discrepancy that should be cleared up. Some of us are discussing the same argument but different sides of the coin.

 

Warped describes a disc with UNIFORM thickness, but with runout. Like a vinyl record that gets hot. A warped disc doesn't cause brake pulse because the calipers are designed to let the pads follow the surface.

 

A rotor with bulges or depositions that change its THICKNESS will cause brake pulse, but that is not caused by heat, dragging brakes, or water puddles. That is caused from deposition of material.

 

I just wanted to maybe get us on the same page. A WARPED rotor doesn't change thickness, it only alters from flat. Its no longer a flat surface. A distorted rotor or one with depositions/inclusions on it has different THICKNESSES and will cause brake pulse. The spinning rotor is trying to squeeze thicker parts through the pads that you are applying pressure to. If its warped, the pads just alter their position to follow the rotor, but it doesn't necessarily alter the friction being applied to the rotor.

 

I think that's the difference. Die-hard techs call any rotor that needs to be turned a "warped" disc. Nothing has changed, its just a greater understanding which has caused us to apply a more accurate terminology.

[SinisterSS]

I understand there are 2 sides to this.

 

Yes they warp.

 

No its the pads.

 

Saying that they warp, you have seen it, is not valid. Please explain with detail how you know the composition of the warped rotors high or low spots. The article does this with clarity. The posts that say, yes they warp, I have seen it, are bogus.

 

Again, this is a discussion. I am willing to be swayed with evidence. I have no stake in the outcome of this, so lets keep it civil.

 

there is a honda/acura service bulletin out for brake pulsation, the bulletin tells us to cut the rotors and test drive the car if the vibration is gone (99.9% of the time the vibration is gone)then the car is good, if not then replace the pads with a rotor resurface.

[Aaron]

there is a honda/acura service bulletin out for brake pulsation, the bulletin tells us to cut the rotors and test drive the car if the vibration is gone (99.9% of the time the vibration is gone)then the car is good, if not then replace the pads with a rotor resurface.

 

which is cheaper for Honda? Turn the rotors? or replace the pads?

 

Money could be the reasoning behind their bulletin.

[Cordell]

I beleive in my experience that brakes develop a pulsation based on a non-flat braking surface, I call it warped you can call it whatever you like. This is caused by a few different things, heat, mis-torqued lug nuts, and junk chinese rotors that can't take the abuse of normal braking. It is also my experiance that replacing rotors and pads to fix a severe pulsation is the best because severe pulsations normaly return to a turned rotor. Lesser pulsations can be fixed by turning the rotor and scuffing or replacing the pads. Regardless the cause I don't see how the fix would be any different. This is the way I do brakes and along with making sure the hub is cleaned and things work the way they should, my customers are happy.

[Guest Whine]

i cant believe this is being discussed. the only way to prove is with a run out gauge or a brake lathe. if pad material is on the rotor as you say then the thickness would grow right?

ive never seen a rotor measure thicker then nominal thickness. its always less because rotors wear right along with the pads. come on man, think about what your saying.

[Aaron]

i cant believe this is being discussed. the only way to prove is with a run out gauge or a brake lathe. if pad material is on the rotor as you say then the thickness would grow right?

ive never seen a rotor measure thicker then nominal thickness. its always less because rotors wear right along with the pads. come on man, think about what your saying.

 

So you are saying that one of the largest brake manufacturers, and race suppliers overlooked your simplistic argument? Think about what YOU are saying.

 

Of course the rotor gets thinner with wear. That is obvious. What I am saying is that the metal itself isn't bending, pad material is on the rotor. So if the rotor is now at 75% thickness after 50k miles, if it was "warped" lets say it is now 75% thickness on most of the rotor, and 76% thickness at one spot on the rotor where pad material was on the rotor. This would cause a pulsating pedal.

 

I will trust stoptech before "I SEEN IT."

[V8 Beast]

Kilkare warps rotors.

[Farkas]

This seems like common sense to me.. Heat is obviously going to cause warpage of metals. I also believe what Aaron might be saying is true, but in special, less common instances.

[Mr. Jones]

Kilkare warps my crappy rotors.

 

[V8 Beast]

 

Not mine, but I've seen it done.

[Mr. Jones]

Not mine, but I've seen it done.

 

:gtfo:

[V8 Beast]

:gtfo:

 

http://www.autopartsmanufacturing.com/productsimages/bicyclebrake_72354.jpg

[Mr. Jones]

http://www.rutlandcycling.com/ProductImages/thumbs/giant_mph_3_164mm_rotor.jpg

[SinisterSS]

So you are saying that one of the largest brake manufacturers, and race suppliers overlooked your simplistic argument? Think about what YOU are saying.

 

Of course the rotor gets thinner with wear. That is obvious. What I am saying is that the metal itself isn't bending, pad material is on the rotor. So if the rotor is now at 75% thickness after 50k miles, if it was "warped" lets say it is now 75% thickness on most of the rotor, and 76% thickness at one spot on the rotor where pad material was on the rotor. This would cause a pulsating pedal.

 

I will trust stoptech before "I SEEN IT."

 

again with stoptech, what do they research their own product? they work in the racing field only I assume and not standard everyday daily driving vehicles that see a lot of stop and go traffic