I have just over 10k miles on ATE discs, and the rear ones are warping on me! I would have thought the front ones would be the set to warp because they do most of the work. They are not to bad yet I only feel it when I get on the brakes hard. I think I will just pick up a set of OE discs this summer and swap them out. I want to paint the tops anyway because rusted discs look like crap. I might as well do the calipers while I'm at it, they are not in that great of shape either. Although the pistons are not frozen.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

How do you know it's the rears that are warped? If they're pretty new than just have them turned. You're not going to affect the integrity of the rotor by taking off .0010". (is that 10,000ths of an inch). Anyways, that's all they take off when they turn them.

Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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.0100"

Hattie, the disc would have to be badly warped on the rear for you to feel it while driving.

Set up an indicator on the face of the disc and see what it reads before you condemn the disc as bad.

The rear rotors on our 83 are warped, you can feel it whenever you slow down, and a whole lot when you have to use the brakes harder....my dad won't replace them however, he said "they stop just fine, I don't care if they are warped." haha.....When mine were warped I swapped them out right away....I'm a spendaholic.... I'll be replacing my rubber lines on all 4 calipers within a month or so, as I am sick of my mushy pedal.....plus the rear ones have a number of stress cracks in them, so I am also very paranoid.

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-diesel is not just a fuel, its a way of life-
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Hattie:
10k for a set of rear (or even front) discs seems very low to me. Are you sure one or both of your rear calipers isn't sticking causing one pad to be stuck on slightly all the time? Also, is the emergency brake sticking on causng heat build-up?

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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

Also you should have inspected the 4 tires for out of round or for uneven wear (if you haven't done this) this can cause the “warped rotor feeling”

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2000 430 ML
2005 S500
87 300 D
61 300 restoring

They'll warp if the wheels are put on with an impact wrench. I would measure the runout before i condemm the disks.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

No it isn't the wheels, I have rotated the wheels once and it didn't change anything with my summer rims. Also no impact guns, my lug bolts are torqued to 90 or 100 ft pounds I don't remember.

I have inspected the rear brakes I don't think a caliper is sticking.

I think they are just starting to warp because under light braking I don't feel much. But when I get on them like coming to a stop at the bottom of the hill I live on they shake the rear of the car pretty good.

I don't have an indicator; are they expensive? Rear rotors are like $70 so I don't want to spend $100 on a guage to tell me to replace $70 worth or rotors. I have never had good luck with turning rotors, for $70 I think I will just get new discs.

Hmm Fastlane sells cross drilled rotors for W126's! I wonder how drilled in the back and power discs in the front would look?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

For a 1987 300SDL, the wheel lug torque is 80 ft. lbs.

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Paul 1987 300 SDL; 2000 ML; '69 MGB; '68 VW Fastback

Rear rotors for my w126 were 30 bucks for two german disks, brand spakin new.
My source was halsey import parts here in portland

Did you break your brakes in properly when you changed out the pads last?

I was gonna make reference to using the lug wrench to put the lugs back on (I do this personally) but I think a different thread already discussed "feeling" torques.

BTW that guage would come in handy for a lot of things...most noteably checking your timing chain stretch
I have a magnetic one with an on/off switch with a dial indicator and plunger attached to a few adjustable arms...
Great tool, especially if you do a lot of lathe work

Yeah but these would look so cool!
Brake Disc X-Drilled Zimmermann Cross Drilled IN STOCK $57.94

I'll swap them out when I do the rear wheel bearings. The current discs are not that bad so I am in no rush.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

...and torqueing them to 100 ft lbs or so could be causing your problem (if they are indeed warped).

As suggested, I would definitely measure them with a dial indicator (or have them measured if you don't have or can't afford one) to verify that they are warped. Harbor Freight has a decent, inexpensive dial indicator.

I always check my lugs with a torque wrench after my free rotate and balance at Discount Tire. They know I'll be checking them, so I haven't had over-torqueing problems in quite a while.

Wes

I had a bent rim (wheel) that gave this impression.

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Ron
2015 Porsche Cayman - Elizabeth
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