AC_S5

Usually when you do a brake job you would:

1. Change the pad.
2. Put the rotor on a lathe to smooth out the surface of the disc so that the new pad could be bedded in perfectly.
3. Change the brake fluid.

As the price of rotor has come down, no one now bother to put the rotor on a lathe. They just change the rotor and also you can only grin the rotor so many times with a lathe before a new rotor is needed.

So now when they do a brake job they just take out the old disc for a new one to save time and avoid unnecessary problems/lawsuit. Imagine if you own a shop and you done a brake job for a customer and the guy got into an accident because there's some problem with the brake disc, will they blame the manufacturer who made the disc? Or the guy who put the disc on the lathe to save his customer a few bucks? My guess would be the latter one.

fraseman999

Changing the disks every time you do the pads is rubbish. If the disks are scored or below minimum tolerances then they need changed. I would guess on normal driving and if your not crazy with the brakes you shoul be changing the disks only every 2 or 3 pad changes.

KAF

BMW maintenance Packeag say change Discs 'If required'.

My pads were changed at 18,000 when the brake fluid was changed but the discs were not changed.

I feel sure they would measure wear and only change if needed.

aybeesea

Hmmm... I've done over 10,000 miles and my brakes (F & R) are showing another 30,000 to change! Maybe I should drive on my brakes more.

If BMW were to change discs every 3 pad changes, at this rate I'd be needing new discs at 120,000 miles!!

ABC

MDT

I think the whole auto repair industry has slowly convinced everyone to just change everything when you have a brake job. In my opinion, I think it is not necessary to change the rotors unless they are scored, warped, or worn down below spec. I remember when disc brakes were introduced (ya I know I'm aging myself), one of the big advantages they talked about was being able to just change the pads if you did it before the rotors were scored.

As far as actual experience, I have seldom done anything other than just change pads. I have gone over 100,000 miles on cars with just changing pads, and the rotors were still in spec. These have included heavy vehicles like 1 ton Dodge van, Sequoia, Ford Expedition, and they have also included light vehicles like Honda, Audi, and Porsche. Of course there are times when you feel a pulsation in the brake pedal and you need to turn the rotors because they are warped. Other times the rotors can become scored and they need to be turned. If turning the rotor makes them thinner than spec, they need to be replaced. But, if my brakes are stopping fine, with no squeels or pulsation in the pedal, I just have the pads changed. I have never had a problem doing this.

Maybe the dealers change everything because BMW will pay them for it under the service plan. They could find many reasons to tell the factory the rotors were not in usable condition anymore and thus generate more income.

Of course, this is just my .02 as I am not an expert, but have just owned a lot of cars over the years and have had a lot of brake pads replaced.

colejl

ah, but remember the iDrive service countdown is crazy! Next week they'll tick down to 10,000 miles..................

Robert A

I got a lot of flack for this from the bimmerfest folks several months ago, but when my front brake pads were worn out at 42k, my independent BMW mechanic, whom I trust, said the rotors were a fraction under spec. I declined to change the rotors.

People in know pointed out that under spec rotors don't dissipate heat as well, but my argument is that I don't recall ever overheating the brakes, and drive conservatively.

I think current pads last so long that that the rotors usually do fall out of the spec by the time the pads have to come off. If you later decide to replace the rotors, before the new pads are worn out, you have to replace again. Par of the decision is that you have to consider how long you'll own the car, and how you drive. Nobody who buys your cars is going to measure the thickness of the rotors.

My feeling is that as long as the rotors are not warped and are close to spec, I just keep on using them. But most people in that circumstance would probably disagree with me.

aosman

I am not an expert but it was explained to me that BMW design their rotors much thinner than others. My understanding is that they do this intentionally so they don't leave much room for turning rotors and force owners to replace them whenever the pads are worn out (warranty service or not). It seems like they did it this way so their cars always have superior braking feel and performance. Turning rotors is never perfect. There is bound to be errors due to operator not setting the rotor correctly on the machine or the turning machine is old and not very accurate. So BMW want us to enjoy the ultimate driving and always smooth braking experience!

Also I've been told that if the rotors are not replaced or turned correctly with a new brake job, the new pads wear out faster.

olli_535d

Had my rear pads changed recently at about 32k miles and they required pads only. Discs still perfectly fine.
Fronts show another 11k now (35k miles on clock now) and I wouldn't be surprised if they needed discs, too, when due

Unlimited

I had a 1982 Mercedes Benz and they as well would change the rotors when doing a brake job, this seems to be an industry standard with these types of luxury cars. I for one after my brakes are changed don't want to think about why my brakes are pulsing, squealing or grinding within months because of a couple of dollars or having to make trips back to the dealer. They Built these vehicles and warranty them and maintain them. I would have to say if they sponsor the costs of the rotors while under the maintenance plan or under warranty there must have been some extensive testing prior to taking on these responsibility.Other posting state that in the norm this is not neccessary but as we all know BMWs are not within the norm they are exceptional.