Warped rotors again

I not afraid to spend the money and buy OEM parts for my cars. I do notice though that even when buying OEM rotors and pads I have a problem with the rotors warping after a few months. This has happened on most of my recent cars regardless of make and model.
I'm looking for a way to remedy this.
Do I stop buying the stock pads and get aftermarket pads that are softer-which ones?
Is there a better aftermarket Rotor company? I did buy Brembo rotors that were cross drilled a few years ago and they lasted a long time.
Is there something else to look for?
I'm not driving like an idiot, just commuting and doing what I think is fairly normal driving.
Thanks in advance, Eric S

Welcome to AF, posting the year and make would help here as many brake system designs lend themselves to this issue. Improper wheel torque procedure, over size tires and wheels, driving habits, failure to clean the mounting surfaces, worn hardware, loose wheel hubs and/or bearings, improperly adjusted or poor rear brake performance, to name a few generic issues.

if you have warped rotors consistantly on multiple cars, assuming there's not a caliper issue with all of the cars in question, which seems unlikely, that only leaves the driving style

If you are a two-footer (one foot on the gas and one foot on the brake at all times), I wouldn't be surprised at all personally

Another issue could be the fact that the rear brakes are not doing their job and putting more load on the front brakes and creating heat to warp the rotors. Make sure the rear brakes are functioning, the cylinders are moving and not stuck and the adjusters are working, and are adjusted up.

Some cars rear brakes are adjusted when the car is backed up and the brakes are applied. I believe that other vehicals rely on the parking brake being applied to adjust the rear shoes up.

Regards

Dan

Rotors don't warp unless you have uneven torque distribution on the hub. If you can rule that out then you have a buildup of pad material usually caused by improper break-in. You can usually have them turned.

If you want good OEM replacement then try Raybestos. They aren't expensive and they do a great job. Get the Quiet Stops for pads and PG Plus for rotors.

Big old myth.

Warped rotors don't cause brake pulsation. They can't because of the design of the brakes. The floating calipers will put even pressure on the rotor, and float along with the warp. Fixed calipers will transfer fluid to the other side if the rotor is warped, but either way, you are still applying the same pressure to the pads, the pads are providing the same pressure to the rotors, so the problem HAS to be an uneven coefficient of friction over the surface of the rotor.

What causes brake pulsation is deposits on the rotor. You probably can't even see them, but the extreme heat burns pad material into the cast iron rotor. It has a vastly different coefficient of friction and therefore causes brake pulsation. In extreme cases, the deposition can be great enough that it alters the thickness of the rotor. In those situtaions, you typically feel it kicking back through the pedal in addition to pulsating brake torque.

The single most important factor in not getting brake pulsation is to properly bed in your pads when they're new. Not doing this step will almost always eventually lead to trouble.

Do a search for "warped rotor myth" and you'll turn up tons of tech on it.

Big old myth.

Warped rotors don't cause brake pulsation. They can't because of the design of the brakes. The floating calipers will put even pressure on the rotor, and float along with the warp.

curtis, you usually give great advice, but this is so wrong I'm speachless.

Just because a caliper is floating doesn't mean it can compensate for warped rotors.

Simple experiment, purposely chuck a rotor in a lathe and cut a .010" runout into the rotor then go drive it. You'll be quite surprised, I assume, to find it will pulsate like crazy with *any* caliper setup

Using "warped" in a sense that the rotor is of uniform thickness and merely bent may slightly cause a pulsing feel.

If the rotor is "warped" in the sense of varying thickness as it goes around has no choice but to cause a bad pulsing.

The floating caliper may follow a bent rotor ok , but still isn't good. A caliper that runs on a rotor with much variance of thickness must push and pull fluid.

curtis, you usually give great advice, but this is so wrong I'm speachless.

Just because a caliper is floating doesn't mean it can compensate for warped rotors.

Simple experiment, purposely chuck a rotor in a lathe and cut a .010" runout into the rotor then go drive it. You'll be quite surprised, I assume, to find it will pulsate like crazy with *any* caliper setup

Flawed experiment... by cutting a .010" runout, you aren't adding .010" to the other side, therefore you are artificially creating inconsistent thickness. That WILL cause pulsation, but I've measured as much as .025" runout with no pulsation, provided its consistent thickness.

If you have a pulsating rotor that measures no runout, send it to me. I'll put it under the scanning electron microscope here at the college and send you photos. You can't normally see inclusions, but they're there. My research has shown me that a "warped" rotor with consistent thickness almost never causes pulsating brakes. If it does its at very low braking efforts where the brake torque being applied is only a small percentage of the pressure required to overcome the movement of the floating caliper, but if you consider the huge brake torque compared to the resistance to caliper movement, its no contest.

The thing is, you measure runout, hear "brake pulsation" and then you machine the rotors to find that the pulsation has disappeared. The logical conclusion is that the warping caused the problem. The actuality is that the runout accounts for little or none of the problem. The inclusions from the pads alter the friction on the surface of the rotor. Machining removes those inclusions and the friction returns to a consistent coefficient.

I did lots of research on this, including looking at about 45 rotors under a scanning electron microscope. Feel free to disagree all you want, but you won't change my mind :) You can put a pretty severely warped rotor on and as long as its a consistent thickness and friction surface, I have not noticed any pulsation, even on fixed, 6-piston calipers on a race car.

. Everytime I have run into this in the field, I have checked the runout or variation with a dial indicator,( I know this is total runout including the hub/bearing and machined mating surfaces) the runout was .005 minimum and spinning the rotor by hand you feel the variation in contact pressure. Many n/c manufacturers now require on car resurfacing to qualify for warranty claim payment., What is the long term prognosis to correct this condition, both GM and Toyota serious issues with this on the Tundra and GM with the Malibu, both redesigned the rotors as a resolution. Are you saying the rotors are not the problem but the end result of uneven friction material deposits?

Flawed experiment... by cutting a .010" runout, you aren't adding .010" to the other side, therefore you are artificially creating inconsistent thickness. That WILL cause pulsation, but I've measured as much as .025" runout with no pulsation, provided its consistent thickness.

you would of course cut both sides. I didn't think that needed saying


If you have a pulsating rotor that measures no runout, send it to me. I'll put it under the scanning electron microscope here at the college and send you photos.


can't say I've ever seen a pulsating brake issue that didn't have rotors with runout


You can put a pretty severely warped rotor on and as long as its a consistent thickness and friction surface, I have not noticed any pulsation, even on fixed, 6-piston calipers on a race car.

not sure what the 6-piston fact changes....have 12 pistons on the front brakes of my bike, and they are well known for rolling dust seals, causing the pistons not to retract properly, and not too surprisingly, cause pulsation

Most pulsations are do to something similar in my experience. Sticking sliders, sticking pistons, bad master cylinders. Whether you cut the rotor, replace the rotor, doesn't do you much good. the problem will be back until you address the root of the problem

Thats why this conversation is fairly moot. Whatever physical property of the rotor and pad that cause the pulsation, doesn't really matter. Its preventing it from happening again that is the real issue IMO. I assume you would agree, for example, if you have a sticking slider, it should be fixed, or issues will come back

The rotors warping (from my research) does not cause the pulsation. Uneven friction surfaces OR inconsitent thicknesses cause pulsation. Pad deposition is usually the cause of both.

The proper solution is to properly bed in new pads. I agree, bob, that fixing the problem is the way to go.

The disagreement with this myth is still solved by the same procedure basically... cutting rotors (while not the best solution in all cases) will fix the issue... its just that I don't believe that a rotor with runout will necessarily cause pulsation. Its possible that every pulsing rotor you've measured has had runout, but that doesn't prove that the runout is the cause of the problem. Just my opinion.

i agree breaking in the pads is the best thing, also i always have see different methods of final preperation don to the rotor, like me I prefer to go with a non directional swirl, some other techs prefer to do no swirl and use this rotor anti squek stuff that you spray onto the rotor, others just turn them and leave the smooth and put them on, what are your opinions on what the best finish should be.

Always non directional to avoid pad walk issues when the rotors look like a phonograph record.The finish should be very smooth to allow faster pad bedding as the raised machinging marks left on a poorly finished rotor severely diminsh pad to rotor contact till the pad and rotor seat, which could take a while in the most severe case.

OEM rotors should last a real long time. Some cars are notorious for being tough on front brakes. I had a 4-wheel disc Buick that ATE front pads. I wound up going with regular auto parts store replacement rotors and using the best Bendix pads that I could get. As for my spin on cutting rotors, I don't go for a mirror finish on them. On the Ammco lathes I would cut them on 4 while most everyone else cut them on 2, which is a slower feed.

Bob

The proper solution is to properly bed in new pads.

If this was the case, then you would see new cars and bikes with pulsating brakes with under 5000 miles. I've never seen one

Can't speak for cars, but I know for a fact that bikes do not have the pads heat cycled or anything else when they come out of the crate

Not bedding in pads doesn't mean they WILL pulsate. Correlation does not prove causation. I'm not saying that all new car will have pulsating brakes, I'm saying that bedding in pads prevents it.

But... you also bring up a good point. Bikes have thin, lightweight, non-vented rotors. Ever test runout on a hot one? They are out by a good bit since they don't have the heft and mass to hold heat like a big cast iron car rotor. Every time you hit the brakes on a bike, they heat up and get way out of round, but they don't pulsate because of it.

Not bedding in pads doesn't mean they WILL pulsate. Correlation does not prove causation. I'm not saying that all new car will have pulsating brakes, I'm saying that bedding in pads prevents it.


quite the contrary, using your model for brake pulsation cause, it would be just as likely on a brand new car as a car with miles. assuming that in all situations being investigated, there is no caliper or rotor issues in addition to the pad bedding issue. How could it be otherwise in your model?

Bikes may have thin rotors, but they have far less kenetic energy and have massive brakes for what they are. They don't even get luke warm until you use them in an extreme manner.

Not sure about all bikes, but after a casual ride to work, raindrops on my rotors sizzle with a passion.

I've known some factory cars with brake pulsation after very short mileage. Mine went back three times under warranty. The other thing not being addressed in this part of the discussion is brake pad material. Factories use less expensive usually organic brake pad material which has less likelyhood of causing inclusions, but its rare that owners use organic pads when they change brakes. Either they pony up the extra $3 for ceramic or metallic pads, or the shop doing the work upsells the "better" pads with a longer warranty.

Not sure about all bikes, but after a casual ride to work, raindrops on my rotors sizzle with a passion.

I've known some factory cars with brake pulsation after very short mileage. Mine went back three times under warranty. The other thing not being addressed in this part of the discussion is brake pad material. Factories use less expensive usually organic brake pad material which has less likelyhood of causing inclusions, but its rare that owners use organic pads when they change brakes. Either they pony up the extra $3 for ceramic or metallic pads, or the shop doing the work upsells the "better" pads with a longer warranty.

My problem is, you're basing all of this off of one central assumption, and everything you have theorized has no evidence outside of that

You found a physical condition that causes brake pulsation, and from there you lept to the assumption that its due to poor break in. I've yet to see any evidence that justifies that assumption, and it definitely doesn't jive with what I have seen during my years as a mechanic.

I have had many pulsation issues that came back repeatedly, even with different pad compounds, even with rotor replacement, rotor machining, and personally breaking in the pads before giving the vehicle back to the customer.....and then we would do nothing but replace a single component, such as the calipers, or the master cylinder, and suddenly the problem doesn't come back

Your explanation makes no sense in these examples, and I have dozens of them.

I think you assume too much from my singular example. I've had brakes that were fine for thousands of miles (nearly to the end of the pads) that started exhibiting pulsation; often times from visible inclusions with no runout. My stating that proper break in PREVENTS pulsation does not mean that its a cure-all and that not doing it is always the cause.

I'm merely stating that from my research, runout may not cause it, and improper bedding can lead to pulsation from inclusions.

I think you assume too much from my singular example. I've had brakes that were fine for thousands of miles (nearly to the end of the pads) that started exhibiting pulsation; often times from visible inclusions with no runout. My stating that proper break in PREVENTS pulsation does not mean that its a cure-all and that not doing it is always the cause.

I'm merely stating that from my research, runout may not cause it, and improper bedding can lead to pulsation from inclusions.

at what point the pulsation happens in the pads life, still seems like a leap to me on the cause. The cases I'm referring to, often were late in the life of the brake pads.

Again, you are making assumptions that do not necessarily corrilate with your findings. Inclusions being present does not automatically mean improper break-in. How can you verify this?

Inclusions being present does not automatically mean improper break-in. How can you verify this?

That's not what I'm saying. I'm not being argumentative, but I gotta say this again: proper bed in PREVENTS inclusions, not eliminates them. I never said that improper bedding will always cause it, nor did i say that proper bedding won't allow it to happen.

Inclusions can happen for one of many reasons; grease or other foreign material on the rotor, an abnormally hot rotor that is stopped with pad pressure applied, improper rotor finish, many things which could happen later in pad life. I'm simply saying that I believe rotor inclusions are more to blame than warping.

proper bed in PREVENTS inclusions
based.....on......what?

Thats all I want. Is it a leap, or do you have some evidence other than the existence of inclusions?

Like I said before...
I did lots of research on this, including looking at about 45 rotors under a scanning electron microscope

I had tons of rotors from the shop, documented symptoms, driver reports, and runout. Then each of them I fractured into four pieces and used a scanning electron microscope to analyze surface composition on the molecular level at four positions around the rotor. In almost all of the cases, rotors that exhibited runout without significant inclusion variation demonstrated no brake pulsation. Those that exhibited no runout but had significant inclusion variation were the ones that DID have brake pulsation.

As I said before, there is a ton of evidence that says warped rotors cause pulsation, but its all superficial. A driver takes a car to the shop and complains of brake pulsation. The shop takes the rotor off, measures runout and machines the rotor. Bingo, problem solved. The problem is, almost all used rotors will show some runout. It is therefore assumed that runout is the cause. The further assumption is that by machining the rotors true, the lack of runout is what cured the problem. What I believe firmly based on my research is that the convenient side-effect of machining rotors removes the inclusions, and THAT is what cures the pulsation, not the lack of runout.

All I can say is that of the 45 or so rotors I tested, it played out like this. Forgive me for not having my numbers handy... this was in 1993.

-On rotors that had significant runout AND significant inclusion variation, they came from cars where the driver ALWAYS complained of pulsation.
-On rotors that had insignificant runout AND had significant inclusion variation, they came from cars where nearly all the drivers complained of pulsation.
-On rotors that had significant runout BUT showed even inclusion over the rotor's surface, they came from cars where almost no drivers complained of pulsation.

What I'm saying is this... for decades, shops have been taking on brake jobs for pulsating brakes. They measure significant runout and machine the rotors to fix the problem. By default, it is assumed that runout is the cause. It has become so accepted that shops don't even typically measure runout anymore, they just go straight to the lathe. However, since most shops that I know of don't have scanning electron microscopes, they can't see inclusions in the rotor surface. I have seen them and documented it.

Now... to further emphasize another point that has been misinterpreted: Bedding in pads PREVENTS uneven inclusions on the rotor's surface. It does not mean that bedding pads will forever make it perfect, nor does it mean that if you DON'T bed pads your rotors are doomed. Its a break-in procedure just like piston rings in a new engine. Proper break-in gives you the best chance at optimum ring seal and long life, but doesn't guarantee it. Inversely, not properly breaking in a new engine does not mean its doomed to die quickly.

So, I guess what I'm saying is; I want to see your proof that runout CAUSES pulsation and inclusion variation doesn't. You can cite how a rotor with runout had pulsation, but that doesn't prove it was the CAUSE of it. I've done the research, I'm just wondering if you're basing your argument on decades of how shops have assumed it was, or actual first-hand research on the molecular level.

I also have to add that I fully respect your knowledge and experience on this matter and I enjoy the debate. I don't want you to think I'm being disrespectful or argumentative. I'm enjoying the discussing greatly :)

Another view on the initiation of inclusions indicates they can be caused by simply stopping when your rotors are still hot. The lack of airflow can lead to the rotors cooking brake material from the pads.
Even without the brakes being applied there is still enough pad/rotor contact for this to happen.

Interestingly enough a car of mine has begun to suffer pulsation only 10,000km from a new set of rotors (same pads).
I have been aware of the inclusion argument for a while and IMO the way this car is driven shouldn't cause such things to happen. In fact the brakes are used sparingly and much of it is open road with plenty of opportunity for cooling both during and after the occasional hard use (it crosses a 1000m mountain pass regularly).

Bedding in pads PREVENTS uneven inclusions on the rotor's surface.

BASED.....ON....WHAT?!

If you have no basis for the assumption, then just say so.

As for rotor runnout can cause pulsation: simple. While mounting a tire on my bike, I accidently slightly bent one of the rotors. It had no pulsation before the tire install, it pulsated after.

Take a hammer to your bike rotor, let me know what conclusions you draw from it.

BASED.....ON....WHAT?!

If you have no basis for the assumption, then just say so.

As for rotor runnout can cause pulsation: simple. While mounting a tire on my bike, I accidently slightly bent one of the rotors. It had no pulsation before the tire install, it pulsated after.

Take a hammer to your bike rotor, let me know what conclusions you draw from it.

I don't think there's any argument that severe runout causes pulsation, there's only a certain speed that fluid can transfer from one side to the other without being felt. Sliding calipers probably have a higher tolerance.

BASED.....ON....WHAT?!

If you have no basis for the assumption, then just say so.

.

Based on the fact that bedding in pads prevents pulsation. Pads that have been properly bedded exhibit more even deposition on the rotors. That is based partly on customer reports during that test, but also from the fact that 6 of the rotors in my tests were mine, so I know their histories.

I also recall saying this:
My research has shown me that a "warped" rotor with consistent thickness almost never causes pulsating brakes. If it does its at very low braking efforts where the brake torque being applied is only a small percentage of the pressure required to overcome the movement of the floating caliper, but if you consider the huge brake torque compared to the resistance to caliper movement, its no contest.


I think you may have taken my arguments too literally.