What caused warped rotors?
 

Hello,

I have a 560SL that has warped rotors. Bought the car a year ago (about 5k miles) so I don't know the history of the brakes on the car.

The rotors were perfectly fine for almost a year then started warping. It seems to have happened over a week or two. I have always torqued the wheels properly when swapping winter/summer tires, etc.

What would have caused this to happen?? There is about 75% pad left and the rotors are half way between "new" and "replace" specifications according to MB.

On one hand, I'd like to put a new set of rotors on. However, it is starting to seem that new rotors/pads/brake hoses/sensors might be a better idea, since the calipers on the front of this car are $350 and I don't want an old hose to cause one to stick!

Neal

Heat is the reason that most brake discs warp!
Driving style can be the reason for excessive heat build-up.

ALSO "cheap aftermarket" discs can warp very quickly!

I do not endorse this 100% but it is interesting reading

http://www.performanceoiltechnology.com/brakingsystems.htm

Rebuilding your calipers is much cheaper than buying new ones. The caliper repair kit is not expensive at all...maybe $25. What brand rotors and pads do you have right now? Are your pads wearing evenly?

Pads are wearing perfectly even. Not sure what brand of rotors & pads are on the car (I didn't install them).

I'm thinking of skipping the pads since there is so much life left. Am I going to cause any problems by just installing new rotors (and hoses while I'm in there!) Not sure I want to buy pads & sensors when the existing ones are perfectly fine for many more miles.

Any thoughts on doing rotors only?

Thanks!
Neal

Check the rears, too!

Make SURE they are warped before replacing, as bad rear rotors are both more likely and will cause the exact same "warped rotor" feel.

I'd not bother to keep the old pads, as they could very well be the cause, although driving style may have more to do with it. You can re-use the sensors if the wires will coil back up.

In the future, avoid near panic stops from high speed coming to a complete stop and standing there with the brakes applied -- the heat will not dissipate from the area under the pads, and pad material will then stick to the rotor, causing it to wear less than were there is no pad material.

Leaving them too thin will make this much worse, that's why I suggest looking at the rear brakes -- they get neglected much more than the fronts.

American manufacturers tended to use enormous rotors in the early days, assuming that they would last the life of the car. Monsters, most of them, with cast hub (not separable like the Benz or BMW/Volvo, etc). Very thick, so there was lots of metal to turn them flat again, and the pads used at the time didn't wear them like the semimetallics Benz uses do.

Much heavier and much more expensive -- I've seen them cost upwards of $100 and that was twenty years ago.....

European makes always used "disposable" rotors to keep the unsprung weight down, something of very little concern to Detroit in the 60's and 70's when American iron still handled like a wounded whale.

That changed, and they are all simlar today.

Peter

I think the number one cause is the insulating property of the pad against the rotor when stopped with hot rotors. Everything that is not under the pads is going to cool off quicker. If you are really anal about it, you could always leave a little room to roll forward a bit after hard braking.

low mileage for an 87. was it in storage for some years before you bought it?

i ask this because benz had a real problem with rotor warping when they switched over to asbestos-free pads. if my recollection serves me well, this problem occurred in the mid-90's.

i know that my 1986 560sel warped 2 sets of rotors in months. now, i am a fast driver and hard braker, but i had never warped a rotor before. when i warped the 3rd set and took it back to the dealer, the service mgr told me that the problem was with the asbestos-free brake pads...that benz was suddenly seeing a deluge of warped rotors.

all i know is that all the expenses of my rotor replacements were refunded, new rotors were installed gratis, and asbestos-bearing pads were installed.

never had another warped rotor.

if i remember correctly, benz even devised a special device for asbestos-bearing pad replacement so that any asbestos was confined and collected, not exposing the mechanic.

on the other hand, all of this might have been a deceptive explanation. benz might just have been supplied a lot of defective rotors.

others out there might know that story better than i do.

all i know is this, i acquired a 1987 560sec from a widow in 2000. with all of its service records. it only had 42,000 miles. everything about it was as if it had just been delivered by manhattan benz. original battery. original brake pads. original rotors. it was a time warp car. the only thing unoriginal about it was the first vintage cell phone that had been installed in the center console and the antenna that was fitted to the right rear[imagine, the cutting of a hole was countenanced].

i mention this because if you acquired your car where problemmatic pads were installed, and then the car wasn't used very often afterwards, you might have acquired a problem that was solved years ago.

just a thought.

Did anyone read the link in post #3? That is pretty interesting. He claims there is no such thing as a warped rotor. He does seem to be pushing a particular brand of rotor machine at the end so I'm not sure if there is any truth to what he says. Comments anyone?

Mike

Oh, rotors warp, alright. Definitely. Anyone who says otherwise can have a look at the set I took off my 202 a couple of months ago. They were out almost 1.5mm. Horrendous. The new set (MB parts, including pads) I put on warped too, within 3 weeks of putting them on, although the performance is not annoying enough to replace them again yet. They were put on properly, wheels always torqued properly, bedded in properly, calipers checked and bled, etc., etc. They warp. The originals never did. They just wore out. I wonder if MB has gotten a bad bunch from a cheaper supplier to use as replcement parts in the last while.

Thickness variation and runout (warp) will be almost the same on the car as far as vibration and pedal pulsation goes. However, if you measure the runout on BOTH sides and its the same but opposite, you have a thickness variation problem.

Some rotor makers seem to leave the material very susecptible to carbon impregnation, allowing them to form hard spots that the wear much more slowly that un-impregnated spots (the gist of all the metalurgy in the article). This was quite common on GM products in the 80's and 90's -- replacement rotors would "warp" almost instantly. Removing a couple thousandths of material from both sides would usually cure them permanently by removing the hard spots.

This is worth a try, although you must make the machinist understand that you only want the very surface removed, not a complete "turning" job, else they will be too thin when you get done.

I've been told to always rough up the rotors with sandpaper when installing new ones to eliminate the machining marks -- the rotors I've gotten for the fronts on the W124s have tool grooves in them (machined instead of ground to size), and if you don't rough them up with coarse sandpaper, the pads will groan forever. Should have done this on the 280 as well, same problem. Proably a result of the pads following the spiral marks, and they never seem to go away completely.

Try a different brand of rotors next time. Good luck, as the 202/210 cars seem to have terrible problems with rear brakes -- most common problem is squealing brakes that even new calipers won't fix, and I seem to remember that "warped" rotors are a complaint, too.

Peter

I had the same experience recently - they warped within a matter of weeks for no apparent reason. I tried to find out what brand they were and there was no writing on them whatsoever - which according to my parts guy was probably an indication that they were made in China. I replaced them with Balo rotors which have been great. I stuck with the old pads, more or less out of necessity in the circumstance, and contrary to conventional wisdom they have worked out fine.

Don't forget improper tightening of lug nuts-

A quick way to warp your rotors is to over tighten or unevenly tighten the lug nuts. The wheels are a lightweight material that absorbs and then dissipates heat. They are bolted to a hard and dense steel hub that conducts heat.

Not evenly torque to the lug nuts causes the rotors to twist and wave when cooling after heating from braking.

Haasman

Non-stress relieved cast iron will warp the first time it gets hot. Cheapo rotors will certainly not be properly made (as is the case with nearly everything from China -- can't wait till GM goes bust from defective engines!!!)

Replace with OEM rotors.

Used pads are OK, I suppose, particularly if they dont' have much milage on them, so long as the face is still flat. If ripply, or groaning or squealing, I'd replace them as well. If they show significant wear, get new ones, they aren't that expensive.

Peter