5 series brake rotors?

Greetings: Any comments on the replacing-vs-turning of the front brake rotors on a 2001 525i? I'm told by BMW techs that they MUST be replaced at each brake job.
I'm also told by a brake shop owner who works on BMWs among others that it's not always necessary. I need them done but don't want to give BMW any more money than I already have for things which may or may not need doing. Thanks in advance.
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BMW discs have the minimum thickness stamped on the hub so can be easily measured for wear.
It's not worth having them skimmed as any grooves deep enough to need this will go down below the minimum thickness.
I find discs last for two sets of pads.
If you really want to save money fit OEM parts yourself. It's an easy job. Took me a morning to change all four discs and their pads and saved 500 gbp over dealer prices. Wish I could make over 100 an hour at work. ;-)
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wrote:

I agree with Dave. For most german cars, it's NOT good to cut the rotors. if rotors are bad replace, DO NOT CUT.
Good luck, Oskar
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On Tue, 27 Oct 2009 18:13:38 +0000 (GMT), "Dave Plowman (News)"

Or use genuine parts bought from BMW dealer. My local one discounted the parts to the price of aftermarket when I thtreatened to walk away when he gave me the quoted price. I seem to remember it was about 40% discount. I agree with Dave...do them yourself if you've ever tackled brakes before. Very straightforward and you know its done properly. Please reply to group - email address is not monitored Ian
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Thanks to everyone for their advice. I found a local guy who will do them, and I'll watch so I can do it myself next time. $50 per hour, and the parts are at his cost.
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On Oct 28, 8:36am, snipped-for-privacy@googlemail.com wrote:

Oh, one final question. IF I do them myself, is there any adjusting necessary? I ask because last time I did a brake job, MANY years ago, you had to "adjust" them when you were done. But I don't rememeber what that entailed. In fact, it was so long ago, that they may have been drum brakes on an old Cadillac! Just covering all bases, here. Thanks again!
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No adjustment is necessary (on disc brakes). You might check to see if you have too much brake fluid in the reservoir after finishing.
The only place where adjustment on BMW brakes is necessary is on the emergency brake (which is a drum.)
BTW, there are only two brake wear sensors: front left and right rear.
FloydR
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Good to know, Floyd. Thanks.
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BMW uses very soft pads and rotors, so that stopping is good in all conditions. As a result, the pads often last only 15K-20K miles; but usually go 40K-50K. Also as a result of the soft iron used in the rotors, they never last more than two sets of pads before reaching minimum thickness. Often, they will last only one set of pads before their lifetime is used up. Remember, if you use more than 50% of the available rotors' thickness with the first set of pads, you're going to be under specification at some time during the 2nd pad's lifetime, whereupon you will need to change both the pads and rotors in any case.
Since the rotors are cheap (Bav Auto shows them at $55 each, with OEM Mintex pads at $45) you should probably just replace the rotors.
The dealers are a rip-off. Go somewhere else. Or, buy the parts and do it yourself, or buy the parts and take them to a corner shop. They're dead easy to install (except for the sensor, which requires an easy touch not a big hammer - not the strong point of many garages.)
The rears usually last twice as long as the front, btw. Do not change all 4 corners unless the rears are actually gone.
FloydR
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Forgot to address re-finishing. Re-finishing removes thickness. On BMW rotors, it's very likely to result in the rotor going under-spec during the 2nd pad's lifetime, and is therefore not recommended. Occasionally, it is necessary to cure a wobble if the rotor warps a little. Usually re-finishing in those cases fixes it for a while, but it will eventually un-warp or warp worse and you'll have to replace it anyway.
FloydR
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Thanks for all that good info. I would have considered doing them myself, or at least have my local shade tree mechanic do it, but "they" make it sound like because of the ABS it's a technical job requiring a special touch and unobtanium tools. So basically, with the exception of the sensor, I (or more likely my shade tree guy) can just swap out the rotors and pads like a "regular" car?
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Absolutely. The sensor is easy, but just a little fiddling. It fits into the center of the inner pad: it should just slide in. You can re-use the old ones if you want to save $10-$15, but they often don't come out clean or slide in as well as new ones. Also, don't force the electrical connector; you can break the retention tabs or pins.
FloydR
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Floyd Rogers wrote:

That would be the brake-wear sensor, of course. I vote getting new oens and making the job easier.

The disk itself is quite easy - a hex wrench to remove the bolt, and a tap with a hammer and it falls right off.
I don't do a lot of my own mechanical work, but I do do the brakes, because it's pretty easy and saves a lot of money.
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wrote:

Thanks for all that good info. I would have considered doing them myself, or at least have my local shade tree mechanic do it, but "they" make it sound like because of the ABS it's a technical job requiring a special touch and unobtanium tools. So basically, with the exception of the sensor, I (or more likely my shade tree guy) can just swap out the rotors and pads like a "regular" car?
<JS> The brakes on my BMWs are by far the easiest brakes to replace. By far.
If you are not up to the task, then you should find a shop that works on BMWs. I'd resist the temptation to ever go to BigO or Midas or any of the equivelent shysters for anything more complicated than filling the washer fluid bottle. There are two BMW shops in my town that claim to have BMW certification. They use BMW parts and do good work for a fraction of the dealership charges.
There is no rocket science involved in BMW brakes. If you have any familiarity with brakes at all, you can replace BMW brakes with ease.
I echo the thoughts of the others here, do not turn the rotors. If the rotors are in good shape, you might not have to replace them, but if they are worn or scored at all, the material that has to be removed to make them true again will leave them too thin.
As a general rule of thumb, rotors should cost $50 each and the pads should cost $50 per axle. This means front rotors and pads should cost about $150. You can spend more and you can spend less. I'd think twice about going too much less, and more is going to give you parts that exceed the need.
Brembo makes excellent rotors at a reasonable price. They may exceed the $50 price point, but they are a very good product and if you have the money, the parts are worth it. If you are price-driven, Raybestos and Bosch are good choices.
I bought nickle plated, slotted and drilled rotors with pads, for the front and rear, for $200 on eBay. The front rotors weren't true. They were cheap, but not true. they sent me a second set of front rotors that were also not true, but they were free. I took them to the machine shop and got them machined for $35, installed them and they work fine. I took the original set and had them machined also, and I'm saving them for later.
So, you can get parts for less, but you have to know some of the problems that can happen if you're a cheap bastard, like me.
PS My slotted and drilled rotors make a clicking noise as the slots and holes pass the pads. I suppose I could swap sides so the straight edges of the slots don't catch on the pads. Hmmm, maybe another project for the weekend.
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Perhaps to your local 'experts' metric hex keys do represent unobtainable tools. I'd try and find some honest experts.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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There are some fancy tools required if you are going to take the brake calipers apart, but you aren't going to do that so don't worry.
The BMW brakes are fairly easy, BUT I will say that the BMW rotors are generally more difficult than most to turn down properly. So I'd suggest just replacing the rotors if the runout is too high on them rather than trying to turn them down. --scott
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Last time I overhauled a BMW caliper I managed without any special tools. Which ones were you referring to?

In general if they need 'turning' there won't be enough meat left to do this. They have to remain above the minimum thickness for the life of the pads. Although My guess is that minimum is pretty generous.
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Waste of time puting them on a lathe.

Rubbish. Only replace if well or unevenly worn.

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