'83 300D. When I come to a slow stop it feels like my brake rotors are warped. The car jerks and lurches as it comes to a stop instead of a smooth stop. I changed the front rotors and pads, but that did not help at all. I did not check to see if the old rotors were warped before I threw them out. I just assumed they were. Now I'm not so sure. Could it be the rear rotors that are warped? Would warped rotors on the rear cause the same symptoms? Has anyone else had a problem with rear rotors?

__________________
Bruce

73 220D (never left Germany)
81 300D (totaled)
84 300D (Purchased '03, sold '17)
85 300SD (purchased 10/01/03)

Of course it could be the rear rotors warped. They can warp just like the fronts.

Another possibility would be present if you did not THOROUGHLY clean the hub surface before putting your new rotors in place. I replace my rotors so infrequently, that it is also a good time to clean and pack the wheel bearings. Since I'm taking off the hub in this case, I strip everything apart, give the hub a solvent bath and then take it to the steel brush that's on one side of my bench grinder. I clean it until it shines on the entire mating surface.

If the wheel bearings are not due a packing, then you need to otherwise find a way to totally clean the mating surface on the hub before putting your new rotors in place.

Hope this helps,

Larry, thanks for the quick reply. I may have jumped to the conclusion that the problem was caused by the fronts. Have you ever had warped rear rotors? Does it feel the same? I have tried to determine by the feel when pressing the pedal but I can't tell if it is front or back.

__________________
Bruce

73 220D (never left Germany)
81 300D (totaled)
84 300D (Purchased '03, sold '17)
85 300SD (purchased 10/01/03)

As a rule of thumb, you will feel front rotor warpage in your hands at the steering wheel. You will feel rear rotors in your ass.
Get the car up to speed with no cars around then hit the brakes fairly hard. See where you feel it, your hands or your ass.

__________________
'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Yes, typically warped front rotors will cause a shudder in the steering wheel and they can also cause a pulsing feel in the brake pedal. On a 300D the whole front end will probably shudder at a stop. I've never heard of rear rotors warping unless someone left the parking brake on . One way I guess you can check w/o removing the rear rotors is to go down an infrequently traveled road and slowly apply the parking brake and see if you get any pulsing. If they do, then you can be almost certain that they are warped.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

The drums inside the disc will tell you that? I'd imagine it would have to be really warped for the parking brake to be affected.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I guess I stand corrected. I thought the parking brake had a mechanical lever on the brake cylinder that would actuate the brake pads. I've only had the rear wheels off once.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

If the W123 is like the W126 there is a set of drum brakes inside the rear brake discs. There only function is for the parking brake, I just replaced the shoes in mine because they were worn down to the metal! There is a wire coming off each brake that goes to a thing that controls them. (don't know the proper name) It has a bolt on it you can turn to adjust the parking brake.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Right you are! I'm just used to the rear disc brake set up of Japanese cars and I was assuming that M-B used a similar system.

Attached Thumbnails

 

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

As I said in my original reply, Yes the rear rotors can warp. Why would they be immune to warping? Yes, I have seen rear rotors warped.

The descriptions of the difference in feel from front to rear are somewhat valid, but not conclusive. Sometimes you can't tell by feel.

Good luck,

Jerky brakes can be a result of sticking pistons are resultant drag and rotor warp. If you cannot bring the car to a smooth sensation-free stop by modulating the brake pedal pressure, you probably have a sticking piston. This will cause firmer than intended brake application at light pedal. Sometimes accompanied by groaning pads, too.

Usual cause is running too thin on pads or rotors, so that the backing plate on the pads hit the anti-rattle spring. Cocks the piston, so it drags, overheats the rotor and ruins the rubber seals on the caliper. Fairly easy to unstick the piston, but if the dust boot is bad, it will stick all the time.

Aftermarket pads sometimes have a thicker than normal backing plate (or the wrong pads for the application), causing the pad to contact the spring sooner than it should.

Check runout on the rear rotors along with condition of pads and dust boot. One pad significantly thinner than the other indicates a sticking piston, necessitating a rebuild or replacement caliper.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks to all. I put in new rear rotors and pads. Smooth breaking now. No more wobble and jerk.

__________________
Bruce

73 220D (never left Germany)
81 300D (totaled)
84 300D (Purchased '03, sold '17)
85 300SD (purchased 10/01/03)