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  #1  
Old 01-29-2003, 08:12 AM
LarryBible
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Warping Rotors

In well over a half million miles worth of 123 cars, I have NEVER warped a brake rotor. My 124 car has warped a number of them. Here is my theory:

I believe that there must be some sticky caliper pistons that allow one pad or the other to sit against the rotor when stopped, just close enough to draw the heat from one side faster than the other, causing the rotor to warp.

Has anyone else ever seen this to be the cause of warped rotors. I am going to replace my front rotors and rebuild the calipers at the same time.

Your thoughts please.

Have a great day,
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  #2  
Old 01-29-2003, 08:24 AM
Michael's Avatar
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Larry,

Check out this article:
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm
Maybe it isn't rotors but rather pads with insufficient temp capacity?

I thought I'd ruined a set of rotors recently, upon tracking my 500 at The Glen running only Euro-spec front MBZ pads. Left a LOT of pad material on the rotors, and the sensation of warped rotors upon braking was shockingly severe. I swapped over to a set of Axxis Ultimate pads, and in about 500mi. of street driving my brakes are (finally) back to normal. Never would have believed it!
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  #3  
Old 01-29-2003, 09:24 AM
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Michael,

Did you swap rotors when you put the new Axxis pads on?
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Old 01-29-2003, 09:40 AM
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No, I did not (was my post that unclear, or has jsmith not had his coffee yet this a.m. :p )

To clarify, I installed the Axxis pads using the same rotors that had Loads of Textar "Yellow Box" smeared all over the faces, and not very uniformly I might add. These particular rotors are directional SL600/E500 OE rotors that I'd had both slotted & cryotreated, so I really didn't want to toss them. I'm quite happy, and fairly shocked, that this all worked out well.
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Old 01-29-2003, 10:03 AM
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i've only had my first cup, thanks . re-reading your post, it was clear enough, i was just incredulous that it could be a simple matter of swapping pads. i have a friend who recently put cryo-treated rotors on his E420 and they warped (old rotors were ok).

i've suffered through a recurring "warping" problem on the family van using OEM pads. i recently switched to bendix rotors and pads but had the sticking piston problem on one wheel which i hopefully caught in time. i had to get a rebuilt caliper for the one wheel. so far so good.

on the w124 i am about to install PBR deluxe pads and have been worried about what to expect.

cheers
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  #6  
Old 01-29-2003, 10:05 AM
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Larry,

I've only had one Mercedes and it "warped" every set of discs that its ever had - 2 or 3 in both front and rear. (I've never warped discs on any other car). Mechanic replaced them under warranty and replaced two calipers (used) along the way. This is over 80,000 miles with Ate and dealer dics. About 15,000 miles ago I rebuilt the rear suspension and put delaer rear discs & pads and they still warped - and BAD!

Last month I installed 4 new/rebuilt calipers & installed front discs and pads from my parts car (cleaned some of the rust off with brake clean) and they ran smooth and have stayed that way. About 1700 miles ago I installed new Balo rear discs with existing pads and the car is still stopping smooth as glass. I'm still amazed .

So, my conclusion is that something in the calipers causing the problem.
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Old 01-29-2003, 10:12 AM
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jsmith,

I have used PBR Deluxe Pads back when everything was warping & have them on my VW too and they seem to work just fine. I do not think they will contribute to "warping" brake discs as long as bad calipers are present.

Larry,

My alignment mechanic has a disc turning machine so I brought him a set "warped" discs to turn. He said they showed high & low spots more so than warping.
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Old 01-29-2003, 12:59 PM
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If Larry's theory is correct, I wonder if one could expect different results from the later model folks with multiple-piston calipers.

Do the later models have the same frequency of this problem?
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  #9  
Old 01-29-2003, 01:54 PM
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I'm sure Larry has thought about this, but I feel compelled to state the obvious....nobody has yet mentioned lug nut torque. If wheels are impacted on rather than using a torque wrench, warped rotors will be a constant problem, resulting in high and low spots.
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  #10  
Old 01-29-2003, 02:01 PM
LarryBible
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Kestas,

Lug nuts being unevenly torqued is DEFINITELY a source of rotor warpage.

I have been pattern torquing lug nuts since the seventies on anything I've touched with disc brakes. I'm also careful at the tire stores and such to see that I tighten the lugs myself (who says I'm anally retentive?)

So, I'm quite certain that this is not the source of warpage on any of my cars.

Have a great day,
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  #11  
Old 01-29-2003, 02:53 PM
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I agree with Larry. This is the only car I've ever owned that has had such a problem with warped rotors.

When I bought my car two years ago, I replaced the front and rear rotors and pads.

One year later, the front were warped. I replaced them.

Now, my rear rotors are warped and need replacing. It's driving me crazy!!!1
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  #12  
Old 01-29-2003, 03:50 PM
slowlane
 
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Rotors

Larry, I was wondering if you had your rotors machine, as you know the thick and thin areas will cause rotors to warp, and machining old rotors where the metal of the rotors have hard and soft spots from usage, will eventually cause rotors to warp. Brake pads dragging as you described, would heat up the rotors, and not knowing the brake system is over heating. Thus not preventing a rapid cool down of the brake system (rapid cooling of rotors causes warping) could warp your rotors. Good theory, enjoy your drive, timreid
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Last edited by timreid; 01-29-2003 at 05:09 PM.
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  #13  
Old 01-29-2003, 03:50 PM
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<>

The later E320 [ 94/95]went to the larger brakes of the 420
because of the problem..
You may want to check your ser # , as some very late 300E- 3.2s got the bigger brakes....
May be a simple up-grade ???
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  #14  
Old 01-29-2003, 04:17 PM
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Arthur, do you think the upgrade is as simple as installing the larger rotors?

Will it work with the same calipers?
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  #15  
Old 01-29-2003, 04:25 PM
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I will check with Dean [ Local Indie friend I mentioned ] as to what is entailed...
He will know , for sure [ unlees some here get an answer first]
You may want to go to Fast Lane and do some checking, as they have the Ser # change before/after specs....
just look up--" brakes>disc.. list all...." and check against your
#s......
you can cross ref the rest of the brake parts while you are there ... that will give you more info...
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