warped rotors - why? - Page 2 - PeachParts Mercedes-Benz Forum

mespe · #16 06-14-2007, 12:48 PM

I believe if you don't tighten the lug nuts properly,,, i.e. every other one, the rotor can warp, or if the lugs are over tightened,,, Of course a bad rotor from the git-go is self-explanatory,,,

Surf-n-Turf · #17 06-14-2007, 12:49 PM

Quote:

Originally Posted by truckinik

Take them back off, and go have them Turned Down/Cut, 'til the warp is gone. This is generally what better mechanics usually do, right out of the box, before they ever even get to the car the first time. Even brand new, out of the box, there is always something warped about them..

Couldn't hurt. Cheaper than new ones.

deanyel · #18 06-14-2007, 01:05 PM

What is the evidence that they are warped? There's a lot of things that can feel like warped rotors.

rosehill · #19 06-14-2007, 01:06 PM

Sometimes in the summer we wash our cars in the drive-through carwash after alot of braking in which your rotors are exceptionally hot, then immediately the car wash (or hose at home) sprays cold water on them and causes warping. Just a thought. I know it happens, but I don't know the frequency.

gmercoleza · #20 06-14-2007, 03:21 PM

Quote:

Originally Posted by deanyel

What is the evidence that they are warped? There's a lot of things that can feel like warped rotors.

The correct way to determine warpage would be to measure runout. It can be done easily while still mounted on the car.

G-Benz · #21 06-14-2007, 03:57 PM

Quote:

Originally Posted by deanyel

What is the evidence that they are warped? There's a lot of things that can feel like warped rotors.

Pulsing brake pedal when slowing to a stop is usually a good clue.

At highway speeds, the warpage manifests itself into a nasty lateral front-end vibration...at least for my car...

...I had a set of front rotors warp within one year for some reason.

BAVBMW · #22 06-14-2007, 06:41 PM

They warp because you use them. Sometimes it happens. Sorry. Your best bet is just to go buy a couple of new ones and put them on. Others have made good points about puddles, heat, and sometimes just being crappy out of the box, but fact is, they're warped now. Replace them. The chances of getting them turned, and having them be worthwhile are slim. They are a much softer metal than say, a Chevy truck, so they don't turn well. Plus, it's getting harder and harder to find a skilled machinist. Most shops will have the minimum wage kid who's just learning turn a couple of carry in rotors with minimal supervision at best. Besides, if they were't able to handle the heat at full thickness, what makes you think they'll do it once they're thinner?

MV

Parrot of Doom · #23 06-14-2007, 07:25 PM

Quote:

Originally Posted by Will_w202

if I remember correctly, the only thing holding the rotors on is a hex screw of some kind. Maybe 2. Really no way to overtighten that, and it's really small anyway. Lugnut torque would be the culprit, but as always, I hand-tightened them.

That screw holds the disc in place to stop it falling on your foot when you remove the wheel

It is the wheel bolts that hold the disc to the hub.

OP: are you certain they're warped? It seems more likely that a buildup of pad material has occured.

Will_w202 · #24 06-14-2007, 08:09 PM

I know my car well enough to know when a rotor is warped. 95k in 3 years on this one, abuot 400k in other cars of various makes and models.

When I begin to slow down, anything under 25mph or so, I get the usual uneven-feel stop, and then as it comes to a stop it will grab and just - well, stop. You know what I'm talking about, and you also know it IS a warped rotor (or 2)

"you drive you get warped rotors" is not a valid answer BMW. Out of about a dozen cars I have owned, this is the ONLY car that has never warped rotors (until this set), in 90k of driving. I've put more miles on this car than any before it, and ALL of them warped their rotors at regular intervals. I believe what I've heard when MBDOC says MB rotors are superior - so, either my MB shop went to cheap replacements, or I have bad luck.

No sense in any more replies. I'm just going to pay to have them turned. makes sense to me.

speace · #25 06-14-2007, 09:15 PM

I would think you would not have problems with MB rotors and Pagid pads. Heat is generally the big enemy. Those Pagids should be pretty dusty. Do you by chance use dust shields on your wheels to keep them clean?

I have experienced overheating brakes when using dust shields in the past so I have sworn off them. Just a thought...

I have also had an MB dealer years ago to pass non-MB parts off to me as being genuine. I doubt this has happened in your case, but who knows...

deanyel · #26 06-14-2007, 09:41 PM

Quote:

Originally Posted by Will_w202

I know my car well enough to know when a rotor is warped. 95k in 3 years on this one, abuot 400k in other cars of various makes and models.

When I begin to slow down, anything under 25mph or so, I get the usual uneven-feel stop, and then as it comes to a stop it will grab and just - well, stop. You know what I'm talking about, and you also know it IS a warped rotor (or 2)

I'm sure you can identify a pulsating brake pedal but the point is that no one can diagnose a warped rotor simply on the basis of a pulsating brake pedal - there are other possible causes, e.g.:

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Hatterasguy · #27 06-14-2007, 10:36 PM

Did you have someone rotate your wheels in the last 5k miles? An impact gun on those alloy wheels will warp those rotors.

Sometimes it happens, they are cheap replace them.

speace · #28 06-14-2007, 10:36 PM

If this is a 1997 C230 it will not have the 5 allen screws holding the rotor, but the rotor is retained by the wheel/lug bolts. The one small allen screw between the lug bolts simply keeps the rotor in place when the wheel is removed.

Additional things to check are to remove the rotors again and clean under them with a wire brush. Dirt and grit trapped under the rotor can keep it from seating properly. Can you get a runout gauge on the rotors?

Check the wheel bearings too. If they are loose, vibration can occur during braking.

probear · #29 06-14-2007, 11:12 PM

As a rule, heat is the first thing to warp rotors.
You might want to make sure that you do not have a caliber sticking.
Secondly, ALWAYS have the rims torqued whenever they are removed. Having the wrong torque or torqued wrong can warp rotors.
The last thing that I can think of is break in. Rotors need to be broken in correctly to help prevent warping.

Will_w202 · #30 06-15-2007, 01:49 AM

Ok.........breaking them in and also having a possible stuck caliper - these are plausible ideas.

How the heck do you break rotors in? I definitely didn't do anything specia.....

Stuck caliper could surely build up the heat! But the only braking performance irregularity seems to be a lack of braking power (a separate issue, doesnt stop as "grabby" as it did when I bought it with new pads at 61k, was thinking master cyl maybe be leaking but again, another story)

hmm......AMG splitspoke 17s, wide-open spokes, no wheels shields. If anything, I've got the coolest brakes of any w202 (barring a stuck caliper)