Can Warped Rotors Be Turned?

[JMI]

If then are not to bad and there is enough left can they be fixed?

Thanks

[Barney Paull-Edwards]

doubtfull, if they have enough "meat" left they could be machined but then you would to size them and discover they are out of tolerence and have to bin them,oh, and machine them carefully or will overheat them....not worth it if you anchor up a lot.

[Blitzkrieg Bob]

If then are not to bad and there is enough left can they be fixed?

Thanks

I think it would be better to just replace them.

[Evan]

rotors are inexpensive! buy four new

[fkong777]

No. Tried it once. waste of money and time.

[E34N]

If then are not to bad and there is enough left can they be fixed?

Thanks


I'm sure you can .. but...

would you trust the braking ability?
Is the cost really worth taking a chance?
can you stop your car any other way?

[markus]

BMW doesnt recomend cutting rotors.

[Sidney Rough-Diamond]

Can be done, never heard of any good reports after though. Save your money and by OE discs if you do any track work, decent after market if not.

[whiskychaser]

If then are not to bad and there is enough left can they be fixed?

Thanks
When I was a kid a neighbour fixed drum brakes by reveting bits of carpet onto the brake shoes. Leave it to you to work out the analogy

[Zeuk in Oz]

Don't forget to regroove the tyres with a soldering iron while you have the wheels off.

[E34N]

Don't forget to regroove the tyres with a soldering iron while you have the wheels off.


and put the thrust bushings in the freezer for an hour or two to stiffen them up again.

[Ross]

Contrary to what most here say you can as long as you don't exceed the minimum thickness. I've done it with good results.
Having said this you need to remember a few things; a badly warped rotor when trued by turning on a lathe is now thicker in some places than others and will likely warp again, a rotor that just needs the ridge removed and a surface to break in new pads is most feasible.
New rotors are dirt cheap and don't require a trip to the machinist who will charge about half the price of a new rotor.
When I had free access to a brake lathe I did it myself, now that I don't I just buy new.

[Ross]

BMW doesnt recomend cutting rotors.
BMW also recommends 15k oil changes and not servicing some trannys.

[Robert K]

I don't know why everyone freaks out about turning BMW rotors. It can be done and I've had it done a few times over the past 7 years I've owned my 1991 535i. The main question is whether there's enough material to turn them and not go under the minimum thickness spec. Any auto parts store that has the capability to turn rotors will measure them for you and tell you whether there's enough material left to safely turn them. If there is enough material left to turn them, you need to ask what the thickness will be after they're turned and determine whether it's worth it or not. Typically, they'll take at least .060 off of them. As your rotors get thinner, their tendency to warp increases. So if you brake hard often, your turned (and now thinner) rotors may warp again soon. If you drive hard, then it's probably a smarter choice to get new rotors.

I tend to not drive too hard and only make the occassional emergency stop. Therefore, I typically am not putting a lot of heat into my rotors, and heat is what warps them. I recently did some rear end work on my car and found that my spare set of old rear rotors actually had quite a bit more meat left on them than the set currently on the car. But because they had some surface rust and because I thought they might have had some warp in them, I had a shop take a light turn on them to true them up. The only issues I've had so far is a little extra noise from the rear brakes. But once the pads and rotors have bedding into each other, the noise should go away. So trust me, it can be done without the disastrous consequences so many people seem to think will happen.

P.S. As far as the application of carpet to the drum brake analogy, I have no idea what the analogy is supposed to be. ?????????????????

Hope this info helps!

Grace and peace,

Robert K
1991 535i

[Alexlind123]

I have never turned my rotors before, and i probably wont, but i think some ppl here are over reacting just a tiny bit...

[Ross]

I agree. Granted, BM rotors seem softer than others but me thinks it's a case of brainwashing by the Bavarians. It backfired on 'em though because there's a thriving industry of aftermarket suppliers for the rotors.

[Macv]

So how much less is it to just turn the rotors? Personally, it sounds dangerous and unwise when you can find some pretty cheap new ones out there. However, maybe its safe and for a fraction of the price, worth it.

-

[Ross]

Nothing unsafe about it as long as within spec. Costs ten or so dollars aroudnd here to remachine, new can be had for about $25.

[632 Regal]

will cut the hardened surface off and they will wear fast...plus all that other stuff mentioned.

[MPD47]

#1 rotors are cheap, you can do a full set for under $200

#2 Rotors dont warp, please stop furthering the use of this incorrect and misleading term.

[JMI]

#2 Rotors dont warp, please stop furthering the use of this incorrect and misleading term.
OK, so what is the correct term and what actually happens to the "misshaped" rotor?

Thanks

[MPD47]

Deposits. You heat your brakes up, you transfer pad material from the pad to the rotor, which forms high and low spots of PAD material on the roto. "Warped" rotors is a myth, or better a term used by people who dont know better.

[Russell]

had no problem with ATEs that had warped after 25,000 miles. cost me $14 at O'Reileys. This was the first time they had been turned and needed only a small amount removed.

[Ross]

No hardened surface I ever knew about.

[BigKriss]

I agree


I don't know why everyone freaks out about turning BMW rotors. It can be done and I've had it done a few times over the past 7 years I've owned my 1991 535i. The main question is whether there's enough material to turn them and not go under the minimum thickness spec. Any auto parts store that has the capability to turn rotors will measure them for you and tell you whether there's enough material left to safely turn them. If there is enough material left to turn them, you need to ask what the thickness will be after they're turned and determine whether it's worth it or not. Typically, they'll take at least .060 off of them. As your rotors get thinner, their tendency to warp increases. So if you brake hard often, your turned (and now thinner) rotors may warp again soon. If you drive hard, then it's probably a smarter choice to get new rotors.

I tend to not drive too hard and only make the occassional emergency stop. Therefore, I typically am not putting a lot of heat into my rotors, and heat is what warps them. I recently did some rear end work on my car and found that my spare set of old rear rotors actually had quite a bit more meat left on them than the set currently on the car. But because they had some surface rust and because I thought they might have had some warp in them, I had a shop take a light turn on them to true them up. The only issues I've had so far is a little extra noise from the rear brakes. But once the pads and rotors have bedding into each other, the noise should go away. So trust me, it can be done without the disastrous consequences so many people seem to think will happen.

P.S. As far as the application of carpet to the drum brake analogy, I have no idea what the analogy is supposed to be. ?????????????????

Hope this info helps!

Grace and peace,

Robert K
1991 535i

[Bill R.]

I've read Carroll Smith's quotes before too.. runout equal to .022 on both sides of the rotor with no thickness variation can only be termed warped in my book. I've seen it many times in my 33 years of working on cars for a living. Or the permanent distortion in the rotor caused by uneven torquing can also on be termed warped as far as i'm concerned. I'm quite familiar with pad material transferring to the surface of the rotor and thats not what i've seen as warped.




Deposits. You heat your brakes up, you transfer pad material from the pad to the rotor, which forms high and low spots of PAD material on the roto. "Warped" rotors is a myth, or better a term used by people who dont know better.

[Bill R.]

The machining limit is .8 mm or approx .032 thousandths on the e34 rotors so if there's much wear at all they aren't worth remachining. I've done it to new ones just to have a clean up cut of .005 or less but if there's much wear don't waste your time. One of the many reasons they have a minimum thickness on the rotor is so that if the brake pads are completely worn out the piston in the caliper still won't move out far enough to where it could come out completely. In some cases where the rotors are worn beyond the limits and the pads down to the metal the caliper piston can pop out losing all brake pressure on that circuit.