As I understand it, MB designed rotors to wear with pads so that it's a good idea to replace both at the same time....which is what I've done. Is that what everyone around here does? Has anyone had success just replacing the pads and then replacing rotors every other time?

I'm glad to save money where I can....but I hate brake annoyances even more.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I only replace the rotors when they get down to or below spec thickness, which is printed on the edge of the rotor. I bought a digital calipers so I can measure them. The other indication I use to change the rotors is if they get warped at all. You can tell this by the pulsating of the brake petal.

I think the responses you get to this question will vary, but there is a definite bias on this forum toward frugality so I would venture to say that a majority of the members do not change them with each change of the pads.

When I did replace my rotors, I purchased a good quality brand. I stay away from cheap metal that will likely warp sooner. They will be a few dollars more but of way better quality.

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85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

^ Agreed.

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83 SD

84 CD

Ditto!

Although, I will advise anyone with the 123 series to get a micrometer, as the outer edge makes it difficult to measure the caliper thickness when there is a lip, and the non vented rotors are more likely to warp from heat than the SD 126 rotors are...

I agree with the above. But, when I have needed them I have always bought new rotors for all of my Cars and never had any issues with them.
Also, I did not have to buy Rotors for my Mercedes as I found 2 new ones in the trunk after buying the Car.

If you reuse the Rotors and do not have them machined you pads will not last as long and the can be noisy.

I agree with the better quaility Rotors to the extent that if you buy high quality Brake Pads you should have High Quality Rotors.

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84 300D, 82 Volvo 244Gl Diesel

Why do I have the impression that MB rotors shouldn't be machined? Somewhere along the way I've heard reuse or replace, but don't machine.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Because you listen to rumors and old wives tales. Ask one of the rumor mongers to show you in writing where MB prohibits the machining of rotors.

My understanding is that they are made of a softer metal and therefore more effective at stopping. But this makes them last not as long.

I took mine to two different shops to see if they would machine them for me when I had a slight warp. The one guy where I take my cars for inspection told me that he cannot get a good smooth cut on them because the metal is too soft. I went to another guy I know who did some body work for me. He said something about how his machine could not hold them and keep them from chattering, I think he said. So after those two negative opinions, I decided to just get new ones. In reality, they are not all that expensive and probably close to what it would cost to have a set machined.

If I had the equipment to machine them, I would give it a try, but I do not. I would be curious to hear if anyone has had their rotors successfully machined. Certainly they were machined in the manufacturing process.

__________________
85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

I machined the original rotors on my '82 300D twice. When I replaced them after 150k miles, they were still slightly above minimum thickness.

No....various indie mechanics over the years I think.

But anyway....I checked the FSM and wasn't able to find ANYTHING about machining brake discs (replacing and cleaning, but no turning/machining). It seems that the burden of proof should be assumed by those who think it's a good idea. In other words, what we should look for is not a prohibition, but a positive endorsement of the practice by MB.

Maybe it's there and I missed it. Anyone know where MB recommends machining rotors?

http://www.w124performance.com/service/Index/Groups/42BrakeSystem.htm

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

If you follow MB's recommendations to the letter, you wouldn't be asking the question to begin with. You would take your car to a MB dealer and say "Fix it."

MB's recommendations have their bottom line in mind. Not yours.

Do you ever drive with your windows down? Is that a practice positively endorsed by MB?

No doubt the profit margin on new rotors is a lot higher than with machined rotors.

I am OK with your Choice.

I was just saying what I do in General.
As an example if it is going to cost $10 to get a Rotor turned and new ones are $13-$15 I might opt for the new ones.

Another issue not mentioned is that when you Measure the Thickness of the Rotors you are measureing the high spots not the bottom of the Groves.

And, if you add a little bit of posible warpage that would have to be removed; your measuremt ends up being mostly and Educated Guess concerning if haveing the Roto turned will work or not.

Another issue is that Guy that turns the Rotor does not want to do it twice. He is going to make as deep a cut as he feels will get the job done at one time.

So I am thinking of all of the above stuff when I am deciding if I am going to have th Rotors Turned or not.

No recommendation here but just a story.
When I took the Brake and Suspension class in Trade School it was taught by an Instructor who owned his own Brake Shop.
He said that in his shop he would reused Rotors that after they were Turned were slightly below the minimun allowed thickness.
He said he felt that it was still safe because the minimum thickness on the Rotors had some several thousands of safety margin to them.

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84 300D, 82 Volvo 244Gl Diesel

This is not a comment on Brakes but just a comment in general. There is a lot of times I have read on the forum there ar things you should not do on Mercedes.

Because to Me a Mercedes is in fact just another Car/machine to me.

So when someone tells me something cannot be done I compare it to what is being done with other Cars or vehicles and try to look for a reason why it should not be done on Mercedes.

If I cannot find a reason why something I want to do on my Mercedes should not be done I use my best judgment and decide what to do.

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84 300D, 82 Volvo 244Gl Diesel

I continue to enjoy the discussion. For myself, it seems that the slightly increased price to replace rather than machine is worth it. I can pick up a pair of Balos or Brembos for $110. What would I get charged to get two rotors properly machined? Whatever the resultant price difference is doesn't seem worth it. But to each his own....

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Don't forget to include the cost of new caliper and rotor bolts, where applicable. Speaking of positive endorsements, MB positively does not endorse the reuse of those bolts.