Warped Rotors

Power stop very good for the price been happy on my truck that sees a good bit of trail and mud. Seem to hold up well.

 

WOW warped from one hard braking.

 

I am pretty sure this is what I used on my last brake job. Not sure. Going to try OEM this time and really concentrate on my driving habits.

 

Shit this is like impossible in NJ. Sounds like too much work to avoid

 

Seriously? You know me? WOW. I kind of baby all my cars. Even do the slow driving during the car car break in period. Maybe you should be open minded as to where people live that may affect break wear. I drive in a pretty congested area in NJ and also go to Manhattan frequently. Anyway for your own knowledge and maybe helping you sleep better, I have done my brakes on various cars and trucks. Never an issue. I have always used OEM maybe that was why?? Never thought it would make this much of a difference using non OEM but apparently with Tacoma's it does.

 

Do you live in a major city where that gap is filled immediately by lane changers? small town or country driving lends itself to being easy on your brakes. never had an issue with warped rotors until moving close to a city.

 

Lots of misinformation here.

Brake pulsations can be caused by a few different things..."warped" rotors are almost never a thing and are way down at the bottom of the list. Rotors very rarely, if ever, warp. Grey cast iron is a very stable material.

Let's define "Brake Pulsation"....we have the steering wheel twitch side to side under braking and we have the pedal pulsation...both symptoms of 2 different issues, or 2 different stages of a progressing issue.

First, how brake pads work: Brake friction material can be classified into 2 catagories...abrasive and adherent. Abrasive friction is typically used in Euro applications and a few domestic/asian applications that use european brake systems (Ford used a lot of Ate brake systems, Brembo is used across the board, etc..). Before the days of mobile car wash people and drive through car washes at gas stations...just about every Audi/Mercedes/BMW you saw on the road had black front wheels...these were abrasive systems that create lots of dust. Abrasive is just like it sounds...the pad material wears, and so does the rotor. It's not uncommon to see the rotors worn below the minimum thickness spec when the first set of pads are worn out. Abrasive friction works by breaking molecular bonds in both the friction material and the iron matrix in the rotor. When those bonds break, they create dust. The relatively excessive dust seen on these applications is a mix of rotor material and pad material.

Most of the asian and domestic vehicles use adherent friction. Adherent friction develops a "transfer layer"...a layer of pad material transferred to the surface of the rotor during break in. After having established a good transfer layer, as the pad is clamped against the layer of it's own material on the rotor surface, we have a constant breaking and recreation of crystaline bonds to create friction...effective molecular movement of material from the pad to the rotor and back and forth. In a perfect world, we'll see rotors actually a tad bit thicker than new and very little if any pad wear. One notable example of a near perfect adherent pad formulation for the application at hand is the 2000-2015ish GM trucks....it was not uncommon (in non-rust belt areas) for the factory brakes to go 200K miles. Akebono absolutely nailed it developing this formula. The only problem was that since the pads went through so many heat cycles during their extended life, the friction material would develop some cracks and cause noise.

This "transfer layer" is constantly breaking itself down and rebuilding itself...sort of like a snow ball that wears I guess. Under certain circumstances...extremely light braking while cold, extremely hard braking...usually outside of "normal", the pads may act somewhat abrasive and wear the transfer layer somewhat. Once the pads get within their "happy" temp range, they will begin to act adherent and maintain the transfer layer. THE LEVEL OF FRICTION CREATED IS DIRECTLY RELATED TO THE QUALITY AND INTEGRITY OF THE TRANSFER LAYER.

If we have a nice even consistant transfer layer, we will have smooth braking. If we have an inconsistent transfer layer, we will have inconsistent friction levels when the pads are clamped on different points on the rotor and we will have a pulsation. Typically this begins as an intermittent steering wheel vibration, that could progress into a light surge at low speed braking, and will later develop into a pedal pulsation.

What can cause an uneven transfer layer:

Excessive Runout: We can take a perfectly good and dead straight rotor out of the box and install it on a hub we might end up with an assembly that is way out of spec. Without looking up the max runout spec on the Tacoma, I'm going to guess Toyota calls out no more than 0.002" measured using a dial indicator about 1/4" away from the OD of the brake rotor. In order to hit this spec, that hub has to be spotless clean...no rust, dust, scale, dirt, etc. It is necessary to properly clean the hub face before installing new rotors. I use a wire cup brush on a die grinder, but there are other methods that work just fine. I stop cleaning when I can see the original tool marks from machining the hub at the factory on the entire hub face. When the rotor is installed on the hub, snug it up with a few lug nuts and measure runout...ideally we want zero. I've never had an issue keeping it under .0015". Keep in mind, we have manufacturing tolerances in every single part on every single car. The rotor will have some allowance, and so will the hubs. If we notice anything over about 0.0015", pull the rotor back off and install it a different position on the hub (I usually rotate 180° with an even number of lugs) and measure again. If it changes, then we know the hub has a bit of runout. If we can "phase match" the hub and the rotor to end up at zero, that would be ideal. A way to determine the source of the runout is to mark your zero and high spot on the rotor face with a sharpie during the first position runout measurement...then after repositioning the rotor on the hub, see where your marks are in relation to your new measured values....if your zero and high spot are in the same place, all measured runout exists in the rotor itself. If the zero and high spots move or the amount of runout changes, then the hub (or debris between the hub and rotor) is playing a roll. If you can't get below 0.002", need to figure out why and fix it or the brake job won't last long.

Runout by itself won't provide any symptoms right out of the gate. As the rotor wobbles back and forth with the pads applied, the caliper with just float back and forth (in the case of a floating caliper) or the inner pistons and outer pistons will move in and out of the caliper to follow the rotor and the small amount of fluid movement will take place in the transfer circuit of the caliper. Fixed calipers (like we have on the 6 lug tacoma) are less forgiving than floating calipers, but we can still install a rotor with 3 to 5 times the allowable runout and very likely feel absolutly smooth braking with no signs of an issue while driving the vehicle. This is about the point people think they've performed a successful brake job, even though they've failed miserably.

Every time a new or machined rotor is installed on a hub, the dial indicator needs to come out and runout needs to be measured. Its right there in the OEM service manual. How else would you know whether the installed rotor is within specification or not? Certainly not on the test drive, because unless we have a crazy excessive amount of runout, all will be good on the test drive.

If we have excessive runout, there will obviously be a relative high spot on each side of the rotor 180° out from each other. Over time, and depending on the friction transfer characteristics of the pads being used, this high spot will develop a different level of transfer layer than the rest of the rotor. In the beginning, this will present as simply a minor torque variation...light surge or steering wheel twitch felt under light high speed braking, and as time goes on will develop into a pedal pulsation as those high spots pick up more and more friction material from the pads. This is NOT a warped rotor, but a function of the the uneven transfer layer that has developed on the rotor surface.

Rust: The rotor surface needs to be kept clean, which can be a good trick in the rust belt. This is where abrasive systems show an advantage. The transfer layer acts to a minor extent as a rust preventative coating...and any minor surface rust will usually be cleaned off the pads in the first few stops if the vehicle is driven daily. More severe rust that results from caustic road de-icing chemicals (mag chloride brine, etc..) will be too much for the adherent (non-abrasive) pads to clean. Vehicles that sit for extended periods, even in non-corrosive climates, will develop rust on the rotors, but to a greater extent on the exposed part of the rotor than on the part of the rotor hiding behind the pads. This leaves us with a good transfer layer where the pads were shielding the rotor, but with a degraded transfer layer on the exposed portion of the rotor. Now we have a "sticky" spot which will result in a torque variation. There are a few pictures of rust damage in this bulletin I wrote at some point during my 18 years at Centric Parts: https://www.centricparts.com/media/technical_bulletins_docs/Common_Causes_of_Brake_Judder.pdf

Rust damage will be visible.

Now, we can do the most perfect brake job in the world with zero runout....but since our rotors don't use small screws to secure them to the hub, they tend to get knocked around a bit during tire rotations and servicing...About as guaranteed as concrete is to crack, hub faces will develop some rust, since they are bare steel. When the rotor is knocked loose, rust/dust may move around between the mating surfaces and when the wheel is torqued (hopefully) back on clamping the rotor to the hub, we might have induced a bit of excessive runout...of course nobody knows because nobody is going to measure runout after a tire rotation....because it's about impossible. This is one of the scenarios where shit just happens and nobody can really do anything about it.

Uncontrollable friction transfer from coming to a complete stop at high temps
Yes, this is a thing. Will we see it on the street?...very likely not. When we approach track temperatures....which are considerably higher than any sane person will experience on the street, then we risk "spotting" the rotors. Unless the pads are hot enough to where you are seeing smoke or smelling the brakes, then this very likely won't be an issue. Although, I have experience some cheap ceramic pads that would smear themselves all over the rotor and cause a vibration due to uneven friction transfer at normal temps...which is why I don't recommend saving money on pads. There are no standard for brake pads, or any replacement brake parts. The only standards that exist are performance standards that the brake system as a whole must meet on new cars....we can assume the OEM replacement parts will be of the same quality and perform like the original parts, but they are not required to. With brake pads, you get what you pay for. Higher cost pads will have undergone more development, more refinement, and will use higher grade materials and better production processes. Lower grade pads typically suck on many different levels and will typically cost more in the long run.


MACHINING ROTORS: Machining new rotors to "true them up" before installation is stupid, and is doing more damage than good in most cases. Let's concentrate on bench type brake lathes here...NOT On-Car type brake lathes. I can almost guarantee you that I can confirm a new rotor to have less than .001" of lateral runout measured on a test fixture, and walk into 10 random shops and have them fixture that rotor on their brake lathe and measure more than .005" of runout while the rotor is mounted on the lathe arbor. Here's why: Most automotive technicians are not trained machinists! Lathe adapters are not treated like the precision tooling fixtures they are. They should be inspected regularly, wiped down with a light oil after each use and kept in a felt lined drawer so as not to get damaged. Instead they are thrown in a pile on a work bench or slid onto a peg board rod on the back of the lathe bench. They have rotors slammed against them all day and most have been used at least a few times as an adapter of sort on the hydraulic press. Most are not in good enough shape to result in machining that rotor actually making that rotor better than it was...and this is where the "most rotors are warped out of the box and need to be trued up" myth comes from. Take any perfect rotor out of a box (most are for all practical purposes, zero runout out of the box) and fixture it on a lathe with beat up adapters and whatever else ails it, and we'll see that rotor wobble around...it'll take at least a couple passes to get a clean cut on the rotor. Sure looks like it was warped...right?

I had a municipality call us to the table claiming our premium line rotors were all warped. This was a cop car shop that would, per policy, machine the rotors and replace the brake pads every time a patrol car was involved in any sort of high speed pursuit. They claimed that while machining these rotors with maybe 5-10K miles on them, so many passes had to be taken to true them up that they were now below mininum thickness and needed to be replaced. They had started checking new ones as well and saw the same issue, so were threatening to stop using us as their brake supplier citing quality issues. I grabbed my dial indicator rig and traveled to the shop. They had a rotor on the lathe that they'd machined true, but it was now below minimum thickness. They also had a rotor on one side of the car that they hadn't yet removed. I put the indicator on both...the one on the car (used) measured about .001"...barely detectable...good enough. The one that had just been machined and was still fixtured on the lathe also measured up with undetectable runout...while fixtured on the lathe. We took that rotor off the lathe and put it back on the hub, where I then measure 0.014" of runout. We took the other used rotor off the car, which we'd all witnessed had no measurable runout, and installed it on the lathe only to measure 0.013" of runout while on the lathe arbor. Basically, they were taking perfectly good rotors, and "truing them up" by destroying them. The solution here was to add some index marks to each lathe adapter and to the arbor, then assembling each adapter in the inboard position on the lathe arbor with the index marks lined up and using the outboard cutter to face off the adapter surface, thus truing it up. Once this was done, any time a clean (need to clean the rust off the hub mating surface) rotor was installed on the lathe using an adapter that was indexed to the arbor and trued to in that position, we'd have a fixture that held a rotor dead straight. We took that used rotor off the other side of the car, set our depth of cut to 0.002", and cut the whole rotor surface in one pass, making the rotor 0.004" (0.1mm) thinner. Everyone in the shop had a "lightbulb" moment when they realized what they'd been doing on that lathe for the last 10 years. Its not their fault...none of this is part of any training available to technicians, unless I'm the trainer. Bench brakes lathes are great if their accuracy is verified...if it's not, assume they will destroy whatever you machine on one.

On-car lathes are great tools, and if used properly, will result in a rotor/hub assembly with ZERO runout. I was a tech at a Toyota back in the late 90s/early 2000s when Toyota required us to start using an on-car lathe. Pro-Cut was the approved machine and the rep came with the new machine and trained us all on how to use it. One thing that was repeatedly highlighted is that on the 4x4s (this was back when the 4 runners and 4x4 pickups and Land Cruisers all used behind-the-hub mount rotors, like most of the pre-2005 5 lug tacomas and earlier trucks) we could still flag our 4 or 4.8 hours for a brake job, but wouldn't have to disassemble the 4WD hub and wheel bearings and make a mess and repack everything. It was "sold" to us technicians as a time saver, the word "runout" was never mentioned. Problem was, as I later realized...it wasn't a time saver at all, and it didn't do anything more accurately if it was used as a time saver. Wheel bearings all had a little slop in them when vehicles came into the shop for brakes...if this wasn't addressed before machining the rotors using an on-car lathe, we'd end up with a rotor with more problems than they started off with. If we're pulling the rotor/hub off the truck to clean and repack the bearings, we might as well just throw that rotor/hub assembly on the bench lathe because using the bearing races as our datum, a bench lathe will machine a perfect assembly on the splindle axis. Also on floating rotor applications like the 3rd gen 4 runner or 6 lug tacomas or FWD cars, we didn't bother pulling the rotor off the hub to clean all the rust on the mating surfaces.

I've been through a lot of OEM service information, and one that stands out is Nissan on the 350 or 370Z. Nissan's instructions for installing a new rotor (taking into consideration that they are discussing known high quality OEM parts here, not aftermarket) to install the new rotor on the hub and measure runout, marking the rotor as I mentioned earlier if runout was above the limit, then re-indexing the rotor on the hub to see if runout could be brought into spec by phase matching the rotor to the hub, and if not, to pick the best position, secure the rotor to the hub and machine the new rotor on the hub using an on-car lathe to achieve zero runout in the assembly. THIS is how an on-car lathe should be used.

Rotor Quality: At this point in the game, most aftermarket rotors are pretty good. They are all made in China (or at least 99% of them) but the factories have been at it long enough to do a decent job. Back in the late 90s/early 2000s we had some real garbage coming out of china as economy priced rotors....looked like they were cast in gravel rather than fine sand, lots of core shift, pretty lousy. If you compare the casting quality of OEM rotors to aftermarket rotors today, you'll see that they are very close. You basically pick your color, as the "coated" rotor seems to the be new thing as of the last 5 years or so.

There are a few rotors out there selling so cheap that I'm not quite sure how they do it...maybe they found one of those factories in the middle east like we see on youtube casting rotors in a dirt lot. I dunno.

I hope a few people read all this....took me 3 cups of coffee to type it all out. lol

 

It can happen. It did on my 2001 tundra when towing a lightweight trailer under 1k lbs. when a car pulled into my lane just before a stoplight. I slammed on the brakes hard to stop from squashing him like a bug. I guess those rotors of mine were smoking mad as I had a lot of brake pedal pulsing after that.

 

Sorry you're so sensitive. I asked relevant questions and suggested some things that might matter to your situation. If it doesn't fit, then someone else may have better advice. Good luck... I hope you figure it out.

 

Literally, never

 

It's OK you live in Utah so...

 

Indeed. To be fair, when it happened to me, I was on a downhill and its possible the brakes were already somewhat hot when I had to do my emergency brake maneuver lol

 

The stock solid rotors would eventually warp on my early gen1 tundra even without any load in the truck. Toyota used basically gen1 tacoma calipers, and pads when they build that truck which were not big enough for the tundra. I solved my problem well enough by installing EBC drilled, and slotted rotors. I never had another warped rotor.

 

If your rotors are warping and you have been through all of the correct brake pds and rotors for the truck I would look into your rear brakes stopping adequately. If your front braking is taking up more than its fair then they will overheat and cause warpage.

 

Yes. However, in this specific case, it was more so the highway comming to a sudden halt on a very long down hill descent with turns causing everyone to slam on their brakes. Luckily I had kept a good distance but the brakes barely stopped the truck at that point. This happened to me when the truck was new to me and I was messing around with the radar cruise control. Had no idea the truck was cooking the brakes since there was no light on the dash letting me know the truck was applying the brakes. Then when the highway came to a stop, I realized I had almost no brakes since the radar cruise control had apparently been cooking them all the way down on the descent. It was a scary situation but I'm glad I kept a good distance as I believe that's what helped me avoid an accident.

 

This didn't do squat on my tundra. I was constantly checking, or adjusting my rear brake shoes while trying to get a new set of rotors to stop warping. I even changed the drums, and star adjusters hoping that would help. Their solid rotors in that truck just didn't cut it. They allowed too much heat buildup, and not enough heat dissipation. The real cure from Toyota was to replace those entire front brakes with the land cruiser components which was over $2k. The 2nd best was the EBC slotted, and drilled rotors for around $400 if choosing their brake pads. I found the stock Toyota ceramic pads fine.

 

This..the cheap comes out expensive. I'm on 30K on my current ones and getting the pulse/shudder, though they're 4 years old and the truck doesn't get the use it once did. That and it was at Toyota for 3 months so IDK if maybe they were rough putting it all back together.

Off my head I think it was about 140 for the aftermarket pads/rotors and I did do the bed in. Next go round I'll probably just get OEM. My initial set went about 60K total, the next set went 40K and was working fine but noticed at yearly inspection they were on the way out so did it sooner than I really had to per se.

 

FYI - NAPA rotors of any type are junk