Are brake rotors as much a wear item as pads? - PeachParts Mercedes-Benz Forum

JHZR2 · #1 07-13-2004, 12:20 PM

Hi,

I replaced my pads and rotors all around at about 190K. Now I have almost 228K miles.
I had my car in the shop yesterday for a tire rotation. While it was up and the wheels were off, I checked the front rotors. To my great suprise, they have already developed quite a lip on the very outer edge, where the pad doesnt actually rub, and on the inner edge, inside of where the pad rubs.
The pads had almost as much meat on them as when I put them on.

All installed items were form mercedesshop.com - ATE rotors and OE pads. The car stops great, no squeal, minimal dust, but I dont like that lip. It almost seems that it is necessary to replace the rotors when I do the pads (I didnt measure the rotors, but the lip is probably 1/2 mm).

The vented rotors on my truck dont have any lip on them at all after 43K of use!

Is this just an artifact of solid rotor use, or is there something I ought to be concerned about? I'm sure Ill get 60K out of these pads at the bare minimum, but it kind of sucks that the rotors already have that lip. And Id hate to resurface solid rotors; it seems like there is so little meat to begin with on them.

So, do I have anything to be worried about? Does this always happen on these cars?

Thanks,

JMH

P.S. Too bad ATE doesnt make a powerslot solid rotor for these cars. The atom-shaped slots are cut to the minimum rotor thickness, so when they are almost gone, you knwo the rotors are due for replacement.

Rick Miley · #2 07-13-2004, 01:27 PM

The standard Mercedes routine is to replace rotors with every second set of pads. Don't machine the rotors - you're correct in saying there isn't enough material to do that. Rotors are cheap, so I don't mind replacing them. But kind of a PITA with a W123 because you have to mess with the bearings.

rickg · #3 07-13-2004, 02:11 PM

I've noticed the same thing on my SD. Replaced rotors and pads all around some 20k miles ago, and rotors are already getting a lip. But on my rears I found my calipers aren't releasing all the way, hence a far greater lip then the fronts. (rear calipers are next) So you may want to check that too.

#4 07-13-2004, 02:25 PM

I would not replace rotors with every other set of pads unless they are worn beyond spec. It will depend on use and driving style.

It is very simple to measure them with a 0-1" micrometer. Compare the measurement to specs. Replace if they are worn too much. Very simple.

Good luck,

JHZR2 · #5 07-13-2004, 02:30 PM

Yeah, I guess a purchase of a micrometer would be in order (its a great tool to have that I don't own yet. This way I can measure them.

But its good to know that it does occur even on the vented rotors of the SD. How would I know if I had an unreleasing caliper? I had a caliper that wouldnt slide on the pins on my truck that would cause intermittent squeaking and a burning smell from the pads heating up. I havent noticed such things at all on this car, and also, I get 30 MPG typically, so I kind of doubt that theyre dragging. But how would you test or know? Rotor coloration?

I definitely hate messing with the bearings during disc replacement; I never understood how to set them, thus my hesitance. That is why I am kind of upset to see the lip. And I can definitely see why the rule would typically be rotors every other set of pads. I try to minimize my braking, and drive as gently as possible (thus why I can get 30 MPG and my MB pads are like new at nearly 30k), and so Id highly doubt the rotosrs would have that much usable life after two sets of pads with that kind of wear rates on them.

Thanks,

JMH

WannaWagon · #6 07-13-2004, 05:37 PM

It's a simple procedure to remove and grease the calipers to ensure they don't stick. Might as well just make it a regular maintenance item, and in the process you'll find out if any are sticking. Be sure and use high-temp brake caliper grease only.

dc88168 · #7 07-13-2004, 07:25 PM

You should have the Minimum Thickness number stamped on the rotor.
In my case, the front rotors minimum thickness is: 10.5 MM ; and the rear rotors minimum thickness is: 8.3 MM.
I would not change the rotors because of lips as long as the remaining thickness is within the specs.

David

_______________
1985 300D Turbo

franklyspeaking · #8 07-14-2004, 04:17 PM

I don't think most Mercedes brakes depend upon sliding callipers. They have two pistons, one on either side, that make the Detroit sliding calliper kind of ancient and crude technology. At least that's the way my 240D is built.

rhodes2010 · #9 04-23-2006, 01:37 AM

Shop manual says to replace the one-time-use bolts that hold rotor
to hub.

Bolts are a dealer item ?

Do you all replace the bearings at the same time ?

t walgamuth · #10 04-23-2006, 04:45 AM

the bolts should be availabe the same place you get the rotors. the fixed calipers were used mostly on up to 123 and 126 cars i think, after that the floating caliper was introduced.

bearings if kept adjusted and packed from time to time will last a very long time, perhaps the life of the car. after 80 or 100k though they will wear enough to need tightening.

and the lip on the edge is normal. i would think no lip is less normal.

tom w

Brian Carlton · #11 04-23-2006, 07:09 AM

Quote:

Originally Posted by rhodes2010

Shop manual says to replace the one-time-use bolts that hold rotor
to hub.

Bolts are a dealer item ?

Do you all replace the bearings at the same time ?

If you tighten he existing cap screws to spec and use a bit of Loctite, I don't see any reason to purchase new cap screws when you change the rotors. They surely can be had from places other than the dealer, but, not typically in quantities of 12. But, you might get lucky at a well stocked hardware store.

10mm seems to ring a bell........but........it's been awhile.

RUN-EM · #12 04-23-2006, 07:35 AM

If you will take the NEW rotors and have them cryogenically treated....that is where they freeze them to a couple of hundered degrees below zero, slowly let them warm up and perhaps repeat the procedure one more time.. they will last and last. They also will not make half of the brake dust that occurs on our wheels. This procedure changes the molecular structure of the disc and does not allow the disc to "crack" during wearing or makes the disc super hard and impervious to wear. NASCAR does this procedure on brakes because of the increase in dependability....a thing that can't hurt us

. But as I said, the no dust issue and extended disc life is why I do it. I couple the frozen rotors with the porterfield street pads and only have to clean wheels about once a year....and then it is just a soap and water cleaning...very easy. You can look into cryogenics at F O R M Y M E R C E D E S . C O M (remove the spaces) ......Jerry Jones offers this service at a justifiable price.

Regards

Run-em
16983 300SD - aka - SPARKY THE DIESEL

blueranger · #13 04-23-2006, 08:49 AM

where do you get them frozen..

or how do you freeze them.

vstech · #14 04-24-2006, 08:51 AM

when did they go to vented rotors?

t walgamuth · #15 04-24-2006, 09:07 AM

i would have thought the s class had them in 82. but it was sometime around then.

tom w