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  #16  
Old 09-29-2010, 11:38 AM
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Quote:
Originally Posted by shertex View Post
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.
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?

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Originally Posted by shertex View Post
No....various indie mechanics over the years I think.
No doubt the profit margin on new rotors is a lot higher than with machined rotors.

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  #17  
Old 09-29-2010, 12:26 PM
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Originally Posted by nhdoc View Post
I am as big a cheapskate as the next guy but I don't cut corners when it comes to brakes.
So you get all of your brake work done at the dealer?
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  #18  
Old 09-29-2010, 01:25 PM
Craig
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In practice, I replace the W123 rotors with every second pair of brake pads (both front and rear). The W123 rotors are just too inexpensive to bother machining, and my experience indicates that a new set will outlast two sets of pads without any performance issues. In this case, I believe the OE recommendation is excessive.
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  #19  
Old 09-29-2010, 02:00 PM
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Originally Posted by Craig View Post
The W123 rotors are just too inexpensive to bother machining...
That is a totally subjective evaluation and says nothing about the technical feasibility of the practice. Clearly, anyone who finds the practice a "bother" is free to avoid it.

From a technical standpoint, it is entirely possible that a rotor machined on the hub (in the case of front brakes) might have less runout than a new one just installed.
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  #20  
Old 09-29-2010, 02:01 PM
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Originally Posted by tangofox007 View Post
That is a totally subjective evaluation and says nothing about the technical feasibility of the practice. Clearly, anyone who finds the practice a "bother" is welcome to avoid it.

From a technical standpoint, it is entirely possible that a rotor machined on the hub (in the case of front brakes) might have less runout than a new one just installed.
I agree, it can be done. For me, it would be more trouble than it's worth. The new ones are very cheap and work well for me; but it's not the only way.
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  #21  
Old 09-29-2010, 02:03 PM
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I typically change the rears every other time.

I can only remember changing fronts once... they are much thicker than the rears
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  #22  
Old 09-29-2010, 02:23 PM
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Originally Posted by shertex View Post
Why do I have the impression that MB rotors shouldn't be machined? Somewhere along the way I've reuse or replace, but don't machine.
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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  #23  
Old 09-29-2010, 02:30 PM
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Quote:
Originally Posted by tangofox007 View Post
That is a totally subjective evaluation and says nothing about the technical feasibility of the practice. Clearly, anyone who finds the practice a "bother" is free to avoid it.

From a technical standpoint, it is entirely possible that a rotor machined on the hub (in the case of front brakes) might have less runout than a new one just installed.
I know at least 2 people who have said they would never again have their Rotors turned while they were still on the car because they had problems with them later.
I suspect the reason is may Cars have a lot of Wheel Blearing end play/clearance. If you do not remove the end play/clearance before you turn the Rotor I do not see how the turning job can be accurate.
I also do not see how they can line up the Machine accurately either.
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  #24  
Old 09-29-2010, 02:39 PM
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Originally Posted by Diesel911 View Post
I know at least 2 people who have said they would never again have their Rotors turned while they were still on the car because they had problems with them later.
"On the hub" is not the same concept as "on the car."
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  #25  
Old 09-29-2010, 02:48 PM
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Originally Posted by shertex View Post
Why do I have the impression that MB rotors shouldn't be machined? Somewhere along the way I've reuse or replace, but don't machine.
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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  #26  
Old 09-29-2010, 03:31 PM
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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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  #27  
Old 09-29-2010, 03:40 PM
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Machining a rotor should cost about $15.
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  #28  
Old 09-29-2010, 03:45 PM
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Originally Posted by shertex View Post
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....
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.
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  #29  
Old 09-29-2010, 04:56 PM
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Answer

Quote:
Originally Posted by shertex View Post
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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  #30  
Old 09-29-2010, 09:54 PM
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What a timely thread. I have started to feel the pulsing from the brake pedal that would be caused by a warped rotor. If my memory serves me the issue of not turning the rotors was the same on my 89 range Rover (I bought it with 58,000 miles on it) I never saw it writing however everyone I spoke with on that forum said to change them not machine them. So I did. I may go ahead and turn these ( I have access to a quality brake lathe) and report back. The only issue I can see is that I need to tun them and wait while that process is going on. If I buy a new set the whole thing goes smoother and faster. Of course they is only because mine are warped without a doubt. If they were not and were found to be within spec I would just resurface/dress them and save the money.

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