Brake Rotors
 

I recently purchased an 02 E320 with 35K miles. Without purchasing a shop manual, it is difficult to get information on some scheduled repairs. I have looked over the owners manual but it is silent on the issue. When are brake rotors scheduled for replacement? I know the rotors on some cars (especially newer cars) are only made to last a limited number of miles (not thick enough to be turned). When it is time, I will replace them myself. My goal is to order all the parts I will need at one time.

Thanks,

Pull the wheel and look on the circumference of the rotor. Min thickness in mm should be stamped on the rotor.

Correct.
Most people around here are averaging 2 sets of pads per 1 set of rotors. ;)

I have found 2 sets of pads per rotor to be a pretty consistent rule of thumb as long as you do not turn them.

Off the top of my head, I think the rotors are 28mm new and somewhere around 25mm minimum thickness.

.... and what happens when they are below minimum thickness? my ;89 300e now has about 225k km and original rotors .... can't complain about anything except that they are a 'bit' glazed

cheers

If the rotors are too thin, your maximum braking capacity is diminished. The act of braking turns motion energy (of the vehicle) into heat energy (in the brake pads and rotors). As the rotors heat up, their ability to absorb more heat is less. A thicker rotor can absorb more heat than a thin rotor. Under normal circumstances, this heat is transfered to the air well before the maximum level is reached, but in extremes, this heat level can be reached, and will result in brake fade. The rotor minimum thickness is set by the manufacturer to assure adequate braking capacity. If you're not turning laps at the local speedway or continually driving up and down mountain roads you will likely never have a problem with undersized rotors.

Another issue to consider (mostly with Ate calipers) is that the piston in the calipers only has a certain amount of length to it, that is eventually it will come out. I have never tried it, but I have heard that if the pads are substantially below min thickess and the pads are worn to min thickess or below, the piston may overextend out of its bore.

Other than that, the main issue is the heat capacity of the rotors.

I'll go along with MONEY PIT's level headed answer. The mfg has to cover his butt in case a car owner spends time driving through 10,000 ft mountain passes and such. For the average driver rotors that have reached minimum limit are not a risk in my opinion. Also in my 30 years as an MB mechanic, I've never seen a piston pop out of a caliper when pads and rotor have reached minimum thickness. Maybe they should, because that would pucker the butts of people who buy new CDs and neglect their brakes:D

I have gotten three or more sets of pads on one set of rotors. I change pads when the pads are equal the backing. In other words I change at about one third of the pad left. Obviously the width is important as well.
I was curious if any one knows how to extract the front rotors frome a 93 124? I have every thing off but the rotor is froze to the hub. I tried hammering and penetrating oil with no luck. Is there a specific technique to
realese stuck rotors? Do you hemmer from the back only? Any guidence would help a lot.

Chris

I have found that on most of my cars about 80k is all you can get from rotors...I admit I have pushed it...not even realizing there was a problem until they warped...

i have to agree...two pad changes which should be about 60k is more realistic.

if you do a lot of city driving or mountain driving, I guess you would adjust accordingly.

Chris, use a piece of 2" x 4" wood as a softener and hit the rotors from behind with a small sledge hammer. Of course, you already removed the set screw. It's a good idea to have an old towel or something to catch the rotor when it lets loose.