WARPED ROTORS

PEH, you are correct in some ways. My thinking is I like to do my own work, but my time is very limited. Any money I save by doing my own work more than make up for the cost of using parts that I have the best confidence in to avoid a redo in a few months. I would rather spend $50 on a new rotor that $6 on a turn job. If the rotor was over $100, I would definitely do as you suggest.

Recently I had a steering lock go bad on my car, around $60 dollars for the broken part. While in there, I put in a new elec switch, new vacuum switch (diesel cut off), and a new tumbler, all as preventive medicine. Total cost of extra parts? Around $135, peace of mind? Priceless! If a new part goes bad? I'll be kicking myself in the butt for removing a time tested part!!!! In my younger days, I never would have spent the extra bucks, since I had more time than money. Once the kids are out of the house, I will probably return to my more frugal ways! Isn't it funny how we change our approaches as we age?

Thanx for asking!

Had my brakes done last month. My mechanic replaced the front rotors and pads. He says as a heuristic, they are usually good for two turnings and then need to be replaced, depending on thickness.

--Craig

[jeffsr]

Well Andy, it is possible to have a defective rotor which can be an imperfect casting. Heat-cool cycles stress the built in metal distortion and continue to make it warp. One of those metallurgical mysteries. If you replace both and the calipers are applying balanced braking force, you should be OK.

[Arthur Dalton]

Originally posted by andy
I am going to purchase a new set of front rotors and brake pads. I will also torque the wheels myself with a torque wrench according to my owners manual. I appreciate all of the replies. The one thing I am curious about is why only the left rotor has warped and not the right? I'm just worried about going through the expense of new parts and possibly ruining them. Since owning my M.B. and with the help of this site and it's members, I'm am becoming familiar with the DOs and DONTs of M.B. car care. Thanks for you help. I would still like to know why only the left rotor has warped? andy

You may want to check for a sticking caliper,
restricted brake flex hose, and even a loose wheel bearing adjustment.

[P.E.Haiges]

Deezel,

I just got back from OH with another 300SD. That makes 3 now. It was a cheapie but has a good body. When my other 300SD rusts apart, all the good mechanical parts will go into the I got today. So you can see that I believe in used parts.

I guess I won't change. As a kid I used to take 2 or 3 bikes and make one good one from them.

My main philosophy still is if it ain't broke, don't fix it.

It works for me.

P E H

PEH,
Very nice! I wish I could have a place to store a parts car, or my "next" car. I already get ribbed about the five working vehicles I keep in my driveway for me and my wife! I too pieced to gether bikes as a kid and as an adult, I have even saved half worn brakes pads and stuck them in as opposed to buying a new set of pads. I would not recommend this practice though, it was for an old VW rabbit that I kept limping along and just couldn't kill. I would never put more than 1/2 tank of gas in it so when it died I would not be out too much money! It never did die and I sold it to a friend for $100, who sold it a year later to another chap, and so on! I've since lost rack of it, but I know in my heart it is still puffing along!

Keep up the good work!

[P.E.Haiges]

Deezel,

I always use used brake pads until they are worn out and I could never tell the difference in performance from new ones. I've had some that went from car to car. I can understand techs only replacing with new parts because they want to maintain their reputation, but when you do your own work you can use used parts and save a lot of money. If they wear out, I just replace them again. I just rebuilt the front calipers on my '79 300SD and I can understand why someone said to replace them instead of rebuilding them because of the extra labor time needed to rebuild instead of just R+R. But again, doing it myself there is no labor charge so I save money by rebuilding them myself.

I've been waiting to replace the front pads on my '80 300SD for 11 years (114,000+ miles because they were in the car when I got it) and they still are only about 1/2 worn out. They look like they will go another 100,000 miles. I suppose some would to say to replace them just because they have that many miles and are old, but I say: "If it ain't worn out don't replace it".

P E H

Regarding the sensitivity of one rotor to warping, it may relate to a difference between calipers, left side may be dragging more than the right side, or vice versa. Also, check wheel bearing play and ensure that you have perfectly clean mounting surface for rotor on hub. Check that caliper is mounted true, I have found that rust build-up can have a detrimental effect on the perfect alignment required by a precision Mercedes.
As for the longevity of your newly-true rotors, I have had superb results with a few tricks:
( my VW has 411,000 miles on the original rotors)
Any time you haul your Mercedes down from high speed, stop short of your intended point and allow the car to creep slowly.
This will prevent heat soak under the pads.
Do not clamp down hard on the brake pedal after a hot stop, ease it up to aforementioned creep-point, this will distribute
thermal stresses nicely. 1/2 a tire rotation at a one minute stop light is good. If you have to heat up your brakes a great deal like a six mile downhill to a quaint village with lots of cold puddles, do your best to avoid dousing your rotors they can warp due to splash shock, nothing you can feel at the time, but it will come up later. Do not let your car park with driving rain coming in through the wheel slots for days at a time. The rotors will surface-rust except at caliper. This does have an effect on rotor width, even after the pads have knocked off the rust.
(VW dealer ruined my old Passat's rotors after a three week wait
for parts, ouch! they paid for the new rotors. That pedal vibrated badly *after* the pads made the rotors shiny again)
Other than these tips, think " thermal stress" and how to *evenly* bake a pizza in a toaster and behave accordingly.
Colin : )

[Tom Hock]

Colin: I think your suggestions are excellent. I follow your braking tecnique also. My Pontiac has 210,000 miles on original rotors: my Merkur Scorpio has 164,000 miles on original rotors; and so far my ML-320 has 41,000 miles on rotors and pads and there is still over half the pad material remaining, and the braking is silent and smooth as silk.

[jsmith]

i once read a really long treatise on why rotors warp. the bottom line is because they are probably defective. i think it has to do with uneven tempering of the metal. that is why turning a warped rotor is only temporary, it will eventually come back. i've heard many stories that tend to give this credence. if a rotor is warped, best bet is to replace it with a brand new one.

[Mike Richards]

I'm amazed at all of the posts I see here stating that it's just as cheap to buy new rotors as it is to have the existing ones turned? Huh?

Labor rates do vary across the country, but I find it hard to believe they vary enough to matter. I recently had front rotors on an Asian SUV turned for $10 a rotor.

No way I can buy new rotors for this or any other car for $10.

[jsmith]

about turning rotors - yes, it is cheaper and may last quite a bit, depending on your driving / braking habits. it can last up to 25k miles, which is my experience with the family van. it started pulsing again on a recent trip through the mountains of Vermont. actually, the van was shaking quite violently on a long downhill stretch. i finally shifted to 2nd which provided just enough engine braking. i am about to replace the rotors as they are now too thin to turn again...

[turnne1]

I have heard from 3 different dealers that I have used over the years that MB rotors are not designed to be turned......I have pretty much always followed that rule.....but I have gotten two sets of pads from the same rotors before I had to change them which for me is about 75-80K(at about 35-40K per pad set)


Warren
1992 300SD
Columbus Ohio

[pjtib]

I once replaced front rotors to eliminate the pulsating of a warped rotor. Within a month or so, the problem developed again. Upon removing the "new" rotors, I noted a blueish discoloration that indicated to me that they were overheating. I then removed the rear wheels only to find that the rear brakes had seized. All of the braking power was being performed by the front brakes only, and they couldn't handle the heat. As they say, "hind sight is 20/20"... I should have been tipped off to this problem by the nose dive every time I hit the brakes hard.

Paul

[whunter]

This is a subtle reminder to check front AND REAR BRAKES.

edit: a related thread
On repacking bearings...
http://www.peachparts.com/shopforum/showthread.php?t=146112


Have a great day.