Brake rotors - life expectancy

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As a general rule of thumb, rotors will last through two sets of pads. Your mileage may vary.


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There is no spec given for this. There are minimum dimensions that must be observed, and the M3 (E36) rotors have a specific admonition against turning the rotors -- because the M3 has the specific admonition and the other models do not, it seems to me that it might be appropriate is some cases to turn rotors on the other E36 models beside the M3, but one must remain with a minimum thickness that exceeds the number stamped on the rotor. So, turning a rotor might be okay IF the result is a rotor that is thicker than the min. specification -- as a practical matter, I don't see how a rotor can be turned AND retain a thickness that is greater than the minumum.
The life of the brake pads is a matter of driving habits/environment, and the life of the rotors is a matter of the life of the pads. Again, as a practical matter, most rotors will last through two sets of brakes. Rear pads will last through two sets of front pads, so rear rotors need to be replaced every fourth brake job, and front rotors need to be replaced every other brake job.
Obviously, your mileage may vary, but as a general guideline, I think these numbers should work out pretty well.

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I'd like to say a big thanks to everyone that responded to my original post. I'm still a little amazed that BMW use rotor materials that wear out so quickly and (even more amazingly) that owners appear to accept that.
Guess I'm just going to have to come to terms with it as a consequence of driving an otherwise wonderful car ... or just brake less :-)
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Steve G
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SteveG wrote:

I think you missed the point Steve. It is not a design flaw (bad thing) that the rotors wear relatively fast. It is a fact of life if you want good brakes. Cars with brake rotors that last over 100k miles also can't brake worth a damn.
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Malt_Hound > wrote:

It's not that I think this is a design fault - believe me I know all about them, I own a Land Rover - just an outdated way of looking at things. I also don't think it's a fact of life either, not these days anyway.
I feel a bit of empirical experimentation coming on tomorrow. Let's see just how much better the 730 can stop compared to the Disco, remembering that the Landie is considerably heavier than the Bimmer. Maybe I'll see if my son will lend me his Focus too - that's nice and light.
Watch this space ...
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Not only are you comparing apples and oranges, you're throwing bananas into the basket as well. If you are going to select or reject a car because of how often the brake rotors have to be replaced, I'll not be watching this space.
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J Strickland wrote:

cars with rotors that last 100K miles can't brake worth a damn. I would never reject a car simply on the basis that something like the brake rotors (a wearing part) have to be replaced more often that I think they should be - I never suggested that at all - I'm just curious to see their respective braking abilities at first hand.
Whether you'll be watching this space or not won't have any influence on whether I carry out the experiment, or not, either. But I bet someone will :-))
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SteveG wrote:

You'd need to compare two cars with the same size (diameter) rotors and wheels, one with hard rotors and one (BMW) with the softer variety. I'm guessing the big Land Rover would have larger discs, no?
I'll be interested to hear how fast you can haul down the 2 cars from the same speed, even with their obvious differences. If you can't stop your BMW faster than a Land Rover, there's something seriously wrong.
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They don't wear out quickly. I didn't put rotors on my E36 until it hit about 150,000 miles, and when it got slammed at 215,000, the brakes were going strong. But, I drive 40 miles to work on a mostly wide open freeway and seldom need the brakes, and when I see others slamming the brakes on in front of me, I lift off the gas and lightly apply my brakes and avoid the need to apply them with the gusto needed by many of those around me.
If people drive the way I drive, it is reasonable that the rotors would last 3 or 4 pad changes, but it is reasonable that the rotors last 2 changes before you even have to look at them.
Yes, there are times that rotors need to be replaced with each pad-change, but this should be the exception rather than the rule, and indicates aggressive driving -- aggressive stopping to be precise. If the shop is telling you that you have the rotors replaced, ask for the numbers. If you wear the brakes down to the backing plate and damage the rotors, expect to replace the rotors. But if you have the pads replaced before they get to the backing plates, then there is no reason the new pads can simply jump right on the car. If the old pads made small ridges, then it is common that the ridges can be removed when the pads are changed the first time, then the rotors should be replaced the next time pads are changed. Removing these ridges is called "turning the rotors," depending on how deep the ridges are, the rotors might not be able to be turned. I think the common position around here is that the rotors can never be turned, but I am not certain this is true all of the time; it matters on how much material needs to be removed to make the rotors flat again. I think the idea is that if so little material needs to be removed to make the rotors flat, then there's no point in turning them, and if they are worn so badly that they need to be turned, then they are beyond hope. I suppose that if this is the way these guys look at this, then it is true, you do not turn BMW rotors. When I replaced my rotors (front only) they had small ridges that I wanted to clean up, but when they were cleaned there wasn't enough material left. With 150k on the car, I thought I was doing pretty well, so I bought new rotors and went home and installed them.
Rotors are cheap these days, BMW rotors run to about $50 per corner, and give superior braking performance.
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J Strickland wrote:

similar driving styles and you get the sort of lifetime from your rotors that I would expect - but you're the first person in this thread to suggest they can get 150k miles from a set.
The cost is not really an issue as far as I'm concerned on safety critical parts ... if it needs replacing then it needs replacing :-)
Keep driving safely.
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Steve G
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Let me clarify that particular point, 150k miles. I bought the car used with 105 already on it. What I do know is that it went from 150 to 215, 65k, and I was not even thinking of doing brake work, at least not work that included rotors.
I think it is reasonable to suggest that rotors will last through two sets of pads, but careful drivers can get three sets of pads past a set of rotors if they try. I don't think it is right to suggest that one will get this sort of wear, because if they don't they they think something is wrong. One should plan on two sets of pads for a set of rotors, then be thrilled if he can get three sets of pads per set of rotors.

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J Strickland wrote:

Completely understood and agreed :-)
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Steve G
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I guess in the grand scheme of things, it's not that big a deal to replace your brakes every couple years instead of every 5 years. (or whatever the numbers work out to for various people in various cars).
I certainly wouldn't give up any driving pleasure for longer-lived brakes.
-Russ.
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Somebody. wrote:

it'll be 10 years before I change mine :-)
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Steve G
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