brake question

[Hocky]

1994 C180 Euro 194,000kms. A couple of months ago I had the car serviced and the brakes looked at. Was told by the indie that the pads will go a few more months and the rotors still ok, though very thin. I reckon the rotors are really too thin compared with other makes. Are they thin when new or do they wear thin very quickly? Saw a few W202s having the rotors grounded down, mine wasn't as they appeared too thin for this. What is the minimum thickness before renewal? The indie put in 4 new sets of brake wear indicator things when they took the tyres off. Will these work correctly if the pads and rotors are actually almost worn down? How expensive to replace OEM rotors, each corner, plus whatever else is required? On dry roads, the brakes are really good, but yesterday in the wet, they didn't feel very good in stopping the car. Why didn't they put in ventilated rotors which look so thick and safe? Maybe its only 1799cc and doesn't need that kind of stopping power.

[dmorrison]

Rotors do wear down. Usually at about 90,000 you think about a new set of rotors with your 3rd brake job. Pads shoudl last about 30,000 miles, you'll have to convert to Kilometers. That is what we find here in the US.
There is a minimum for rotor thick ness and a minimum for pad wear. The reason for this is that the caliper can only push the pads out so far before the caliper assembly would come apart, leaking fluid and not working any more. that is why the minimum pad and rotor thickness exists. Your dealer should be able to tell you what the minmum for the rotors are. Pads should always be replaced when wear indicator starts to light.
To explain minimums.
The distance between the two sides of the caliper is fixed. The rotor wears slowly, so do the pads. As the rotors and pads wear the caliper must push its piston, that actuates the pad out of the caliper cylinder further and further. At a certian point the piston in the caliper is so far out that the fluid behind the piston can start to seal out and leak. This is bad, No fluid, no brakes. So the engineers set limits for the entire assembly. Don't push thses limits.
We find in the US that it is not worth turning the rotors. They are cheap and its easier to replace them. Once you add the labor to remove, turn and replace the rotor. Your better off putting on new rotors. Anytime you R+R you rotors, put on new pads and sensors. You do not hav to replace the sensors IF they had not turned on. Its a plastic covered wire that the rotor wears down the plastic and turns on the wear light. If the plastic has not been dammaged why replace the unit with a new one. Even though they are only $2.00 each.
Why did they not put on a different brake set up. Tthey designed the brake system for the expected use of the car. If you are pushing the car more or havre modified the performance of the vehicle, Consider a better brake system. If your a normal driver, why waste your money.
Do you want larger and cross drilled rotors, with larger calipers that will stop the vehicle much better, You can have it. The after market industry will sell them to you. But why spend $2000 for a brake system you don't need!!!!!
Ventalated rotors, The ventelated rotors are designed to dissapate heat. You're really braking hard and using the car in a high performance mode to need ventalated rotors.
Understand you entire wheel assembly is the braking capability of your car. The amount of surface the pad and the rotor. The design and wear of your tire tread. The surface of the road. The wet dry condition of the road, and again tread design. How much contaminants are on the road, oil, debris, etc.

Dave

[Hocky]

Thanks Dave for your assistance. I will see my indie soon with the car and have it jacked up to reinspect the 4 brake rotors, pads and all other parts. I reckon that if the rotors were at least 1cm thick, it would certainly last longer and allow more grinding down to occur and normal wear and tear. Mine look like they are about half of that and looks pretty thin. I changed to 94 regular unleaded and it seems to be running better than the 98 premium. Maye the PO has taken off the resistor under the washer tank???

[RKreutzer]

Hi Hocky,

on my 87 W126 the front rotors are ventilated and 28 mm thick at the beginning of their life. MB says limit at maintenance is 26 mm, wear limit is 25.4. Thus you have only about 1.3 mm wear on each side on a 28 mm disc. The rear disc is not ventilated and only 10 mm at the beginning, limit at maintenance is 8.6 mm, wear limit is 8.3 mm. I don't know your model, but this should give you an idea. Your indie should be able to give you the exact numbers for your car.

As for the running with 94 vs 98, you are right, the PO might have had the timing adjusted for running with lower octane fuel with a corresponding drop in power. But running higher octane shouldn't result in poorer running, just the same.
Regards

Reinhard Kreutzer

[Hocky]

Thanks Rheinhart. My indie has given me a cost of about A$515 to replace the front rotors and pads with labour and taxes all in. The backs will be about A$400. What do you think? This will be subject to inspection with me around to confirm the thickness. Thinking of doing the fronts first only due to lack of cash. Think the fronts will definitely be the ones to go off first. What do you all think? Pity I can't do it myself and am not really confident to try it. Labour is A$120 for each end. Tax is 10%.

[yal]

At those prices I would do it myself

Not sure how similar your system is to my 1996 C220 (W202 I think), but I paid less than $300 for full semi-metallic pads, rotors, wear sensors, and lubrication grease for all 4 brakes to DIY.
Granted, it helps, is essential, to have all the proper tools to do your own brake job.
If you are mechanically adept, I would suggest you give it a try. Not having a repair manual for my car I was very nervous about doing the brakes, but using my pat experience on my other (American) cars, I pressed on. Wouldn't you know the Mercedes brakes were MUCH easier to change out.
Even if you don't have the necessary tools, you could spend around $100 for them. This still brings you to a total cost of around $400. An afternoon of car repair is all you should need.

[Kestas]

Confidence comes with experience. We're here to help you with anything you're uncomfortable with. Think about it - you can save probably over $500 doing it yourself. Have you done any wrenching on cars?

All thing being equal, do the fronts first.

[RKreutzer]

Hi Hocky,

On the top of this page there is a D.I.Y block that includes a brake job and there are other members who have web sites with pictures of these jobs (Thomaspin comes to mind). However, the brakes are the most important things on the car and if you are not good at wrenching or don't have a set of required tools, you should have it done by a good mechanic you can trust and who works on MB's regularly. Lets not forget we are talking 500 Aussie Dollars or about US 320. I probably have to pay that in the US too, if I have it done here.

As Kestas said, do the front first if you cannot afford both but get used to the fact that older cars are more expensive to maintain, unless you know the previous owner has already replaced all these "wear out" parts. If you don't do the work yourself, you will have to pay somebody to replace these 200,000 km old parts with new one's, which will then again last 200,000 km.

Good luck

Reinhard Kreutzer