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..