warped rotors - why?
 

I went through 150k on original rotors and 90k on pads with NO issues after purchasing this car under warranty at 61k. I bought Mercedes parts-counter rotors and Pagid pads from Phil's store. They are warped with 5k on them.

WTF?

That is an excellent question. Excessive heat is the Most common answer.

I have never had warpage problems on any of MY cars OR trucks except my Toyota truck & they installed modified rotors, pads & calipers on it & they still warped!

So, heat? Nothing has changed that would cause heat buildup. The car sits on AMG 2002-2004 style split-spoke wheels, which get PLENTY of air. There is no obstruction in either brake vent at the front of the wheel wells.

What can be done? I'm tempted to call the parts counter and find out if they're selling knock-offs.

?????????

It's not so much heat as it is rapid and marked change in temperature. Ever hear an ice cube crack when you put it in a glass of water? That's because the instantaneous temperature differential causes the ice to warp and crack.

Imagine slamming really hard on the brakes, or using them on the highway slowing down from 70mph to 30mph (exit ramp), and then running through a puddle of cool water. The result is going to be warpage. There are a hundred normal everyday-type driving scenarios under which the same result can occur. Which is why I go with the cheapest rotors I can find.

One time, of accidentially riding your brakes down a hill, or getting them wet while they're hot, is all it takes to warp them. ( I.E. Car wash, after some driving, puddle, etc.)

Are you a two footed driver..?

General rule of thumb though, is to cut them once before installing them. I've seen plenty of brand new ones come right out of the box warped, simply from the heat created while machining them at the factory.

well, that's fine, but I bought these because I was told they were the BEST rotors, and as I'd seen 150k on the last set of OEM rotors, which FYI were the ONLY set of rotors on ANY car I'd ever owned that DID NOT warp or require turning, I figured they were the way to go.

My driving style has not changed in the past 5k, and I"ve put 95k on this car. 90k no problem, the next 5k, problems.

No valid explanation yet,.

Like said before, it is just a random occurrence and probably has nothing to do with your driving style. It just happens. The price and build quality of the rotors doesn't have as much to do with warping as we would like to think. Heat up a nice high-performance cross-drilled rotor, run it through a puddle, and it's going to warp just as easily as the $30 KIA rotor.

:(

Well, fact be told, that no matter who's name is on the box, all rotors, and things like that are made in China these days, by the lowest bidder. They start out as a huge chunk of the cheapest steel they can buy, or get away with, and it's inserted into a an even bigger machine, which over a course of the next few hours, spits out rotors one after the other. All they do next, is swap out the tooling, and make them for the next, Year, Make, and Model scheduled for the day's production...

I've visited, and toured many companies of which do this, in many parts of the world, and seen it in person..

It does not matter who's label is on the box, Just like electronic items, like car stereos, and T.V.'s etc.

Did you know that there are only TWO companies in the world producing televisions..? Yet, How many name brands are on the market..? Same thing, just different products.

Do the MB rotors warp if torqued too tight or wrong sequence? I have heard of it happening on other makes/models before. I have never used an impact wrench on lugnuts just for that reason.

As a rule of thumb, any mechanical part which has a specified torque measurement and pattern can warp if these are not observed. I would think it more likely that the wheel would warp rather than the rotor, though I suppose it is possible.

No, You'd have a better shot at snapping a lug, stripping out the nut, bending or cracking the rim, before that ever happened.

Don't forget, that rotor, when installed on the car, is backed by the hub also, which is tempered, very durable steel, and a flat surface to boot. That particular area, of both rotor, and hub, are extremely durable, and it would take quite a few thousand pounds of pressure to do anything short scarring them. Most, if not all times, they don't even bend when the car is crushed in the crusher, and often times ar the only survivors of it. Outside of that area, where the pads, make contact, is extremely vulnerable though. This, is the area that warps, or bends, or even breaks off in chunks, very easily.

if I remember correctly, the only thing holding the rotors on is a hex screw of some kind. Maybe 2. Really no way to overtighten that, and it's really small anyway. Lugnut torque would be the culprit, but as always, I hand-tightened them.

ok, anyway......I know they're not supposed to be turned, but in a case like this, what are my options?

Take them back off, and go have them Turned Down/Cut, 'til the warp is gone. This is generally what better mechanics usually do, right out of the box, before they ever even get to the car the first time. Even brand new, out of the box, there is always something warped about them..

I believe if you don't tighten the lug nuts properly,,, i.e. every other one, the rotor can warp, or if the lugs are over tightened,,, Of course a bad rotor from the git-go is self-explanatory,,,

Couldn't hurt. Cheaper than new ones.

What is the evidence that they are warped? There's a lot of things that can feel like warped rotors.

Sometimes in the summer we wash our cars in the drive-through carwash after alot of braking in which your rotors are exceptionally hot, then immediately the car wash (or hose at home) sprays cold water on them and causes warping. Just a thought. I know it happens, but I don't know the frequency.

The correct way to determine warpage would be to measure runout. It can be done easily while still mounted on the car.

Pulsing brake pedal when slowing to a stop is usually a good clue.

At highway speeds, the warpage manifests itself into a nasty lateral front-end vibration...at least for my car...

...I had a set of front rotors warp within one year for some reason.

They warp because you use them. Sometimes it happens. Sorry. Your best bet is just to go buy a couple of new ones and put them on. Others have made good points about puddles, heat, and sometimes just being crappy out of the box, but fact is, they're warped now. Replace them. The chances of getting them turned, and having them be worthwhile are slim. They are a much softer metal than say, a Chevy truck, so they don't turn well. Plus, it's getting harder and harder to find a skilled machinist. Most shops will have the minimum wage kid who's just learning turn a couple of carry in rotors with minimal supervision at best. Besides, if they were't able to handle the heat at full thickness, what makes you think they'll do it once they're thinner?

MV

That screw holds the disc in place to stop it falling on your foot when you remove the wheel :) It is the wheel bolts that hold the disc to the hub.


OP: are you certain they're warped? It seems more likely that a buildup of pad material has occured.

I know my car well enough to know when a rotor is warped. 95k in 3 years on this one, abuot 400k in other cars of various makes and models.

When I begin to slow down, anything under 25mph or so, I get the usual uneven-feel stop, and then as it comes to a stop it will grab and just - well, stop. You know what I'm talking about, and you also know it IS a warped rotor (or 2)

"you drive you get warped rotors" is not a valid answer BMW. Out of about a dozen cars I have owned, this is the ONLY car that has never warped rotors (until this set), in 90k of driving. I've put more miles on this car than any before it, and ALL of them warped their rotors at regular intervals. I believe what I've heard when MBDOC says MB rotors are superior - so, either my MB shop went to cheap replacements, or I have bad luck.

No sense in any more replies. I'm just going to pay to have them turned. makes sense to me.

I would think you would not have problems with MB rotors and Pagid pads. Heat is generally the big enemy. Those Pagids should be pretty dusty. Do you by chance use dust shields on your wheels to keep them clean?

I have experienced overheating brakes when using dust shields in the past so I have sworn off them. Just a thought...

I have also had an MB dealer years ago to pass non-MB parts off to me as being genuine. I doubt this has happened in your case, but who knows...

I'm sure you can identify a pulsating brake pedal but the point is that no one can diagnose a warped rotor simply on the basis of a pulsating brake pedal - there are other possible causes, e.g.:

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

Did you have someone rotate your wheels in the last 5k miles? An impact gun on those alloy wheels will warp those rotors.

Sometimes it happens, they are cheap replace them.

If this is a 1997 C230 it will not have the 5 allen screws holding the rotor, but the rotor is retained by the wheel/lug bolts. The one small allen screw between the lug bolts simply keeps the rotor in place when the wheel is removed.

Additional things to check are to remove the rotors again and clean under them with a wire brush. Dirt and grit trapped under the rotor can keep it from seating properly. Can you get a runout gauge on the rotors?

Check the wheel bearings too. If they are loose, vibration can occur during braking.

As a rule, heat is the first thing to warp rotors.
You might want to make sure that you do not have a caliber sticking.
Secondly, ALWAYS have the rims torqued whenever they are removed. Having the wrong torque or torqued wrong can warp rotors.
The last thing that I can think of is break in. Rotors need to be broken in correctly to help prevent warping.

Ok.........breaking them in and also having a possible stuck caliper - these are plausible ideas.

How the heck do you break rotors in? I definitely didn't do anything specia.....

Stuck caliper could surely build up the heat! But the only braking performance irregularity seems to be a lack of braking power (a separate issue, doesnt stop as "grabby" as it did when I bought it with new pads at 61k, was thinking master cyl maybe be leaking but again, another story)

hmm......AMG splitspoke 17s, wide-open spokes, no wheels shields. If anything, I've got the coolest brakes of any w202 (barring a stuck caliper)

Will...You didn't do anything WRONG! Look back at what I first posted.

Those rotors were just poor castings. I owned over 20 MB's & never had a warped rotor! EVEN on my racecar! Even in the rain at 140mph!

But that darn Toyota tow truck warpes them all of the time.

You can have then turned (trued) & hopefully the problem won't come back.

I don't care what anybody says, if you don't use a torque wrench on them and set the proper torque, they will warp eventually.

Rubbish. I have never used a torque driver on any wheels on any car I've owned, and only on this MB have I ever had problems with discs. Thats Vauxhalls, Audis, Volvos, and a TVR.

I had a pulsating pedal problem and was convinced it was a warped rotor. I checked with a dial indicator/fixture and there was no appreciable run-out, or what there was was well within spec. I removed the 2 relays from the ABS master 'box' to disable the system and the problem disappeared.

From a mechanics perspective
 

I am ASE certified and for many years worked as a Front End, Brake & Power Steering Specialist. Brake rotor warpage is a problem that has been ongoing since eliminating asbestos in 1990. That's not to say it didn't exist proir to 1990 but it was usually caused by abusive driving, mechanics with uncontrolled air guns, cheap pads etc. One of the problems after 1990 was that the pad material would actually weld itself to the rotors causing pulsations.

Additionally, in the past few years many smaller producers of quality automotive parts have been bought up by conglomerates and as a result quality has suffered. Many of the old trustworthy aftermarket brands have sunk to a new low in quality or just dissappeared. Most all of those left now import from China or Mexico which tend to be inferior. Raybestos still has American or Canadian made rotors as of the last time I bought them. These are still good quality. However many parts houses sell "White Box" Raybestos rotors which are from China or Mexico. Avoid them like the plague. If you follow these rules you will minimise the possibility of pulsation problems.

1. Buy strictly OEM or known quality aftermarket rotors

2. If possible OEM or "Ceramic" replacement pads.

3. Rotors should never be machined below tolerance specs.

4. Wheels should be tightened in a star pattern with an appropiate "Torque Stick" if using an air gun, or torque wrench if by hand

5. Break-in of new pads should be "Gentle" for the first 200 miles. Avoid panic stops. Several slow stops from 45 to 0 with cool down time in between helps the process of eliminating high and low spots in the pads so that the full surface of the pads contact the rotors and help dispense the heat.

It is still possible to have pulsation failures when you follow these but at least you've done all you coould do to prevent it from happening. HTH.

Mbdoc
 

I wasn't countering your post; I was countering someone else's

I'm with you on this. The MB is the only car that had NEVER warped a set of rotors until now. I'm thinking I probably did get defects.

Will have them turned at my 160k service.

I wonder if,,, when a rotor is replaced, if there is a small chunk of rust or other debris inbetween the rotor and the hub could cause warpage. Sounds plausible to me.

Try a Honda.
You will change the rotors more frequently than the pads. ;)

I've had 2 Hondas and they warped them every 5k