rear end sagging

[mbtjc]

The rear of my W126 420 is a lot lower than the front. I am measuring from the top of the wheel well and the bumpers. Is this just a case of worn shocks and rear subframe mounts or what? If it is and I fix that, my rear will be sitting as high as the front, correct? Because if that is the case, it needs a lowering job!!! The rear actually looks right as it is, but I am guessing that is not the way it is supposed to be. If it needs to be lowered, I think I will go with H&R with #2 spring pads, but unsure of the shocks....which ones are best in this case? I don't want to give up TOO much comfort. Anyone?

[JimSmith]

mbtjc,

There are a number of worn components that can contribute to the sagging rear suspension of your car, but the most likely are the shocks and/or the springs. Usually the shocks go first, and if left uncorrected, you can deform the springs permanently.

The shocks have a gas pressurized chamber to prevent the shock oil from cavitating and becoming filled with gas bubbles, which then changes its viscosity and the shock performance. This feature contributes to the superior handling and ride, which is why Mercedes specifies these shocks as OEM components.

As they get old, the gas can leak out, and like any shock, so can the oil. This reduces the contribution of the shock to the force resisting the weight of the car, in addition to the springs, and therefore it affects the ride height. If the shock is really bad for a long time the spring takes the entire load and can eventually spend enough time in a more compressed configuration, leading to yielding of the coil spring material.

So, you most likely need shocks and if oil is leaking that is visually apparent. Just stick your head in there and look around for wetness. It may help to jack the car up and take off the wheel.

I think there are spacers you can buy to raise the height if the shock replacement does not restore the height fully. The spacers go under the coil spring, and this may be a more affordable solution after the shocks are changed out.

Good Luck, Jim

What are the symptoms of bad springs? My car had very bad shocks when I bought it with about 100,000 miles. I replaced the shocks right away. The springs seem ok, but I have nothing to compare it to. If having bad shocks damaged the springs, how would I know?

[JimSmith]

AAL,

The most obvious sign of worn springs is the ride height of the car empty and loaded.

With new shocks the car ride height should meet the specs in the manual, measured unloaded and loaded.

If you drove with shocks that were out of oil and the wheels were banging into the stops for a while, I would find a dealer or MB independent shop with good credentials and have them check it out. If the spring, out of the car is not up to its design free length, it should be replaced, or you can add a spacer to make up the difference in some conditions. I am not familiar with the typical kinds of measurements made on auto springs but would suspect a check of load capacity per inch of compression should be part of the check. This would be more important if the spring free length is ok and the rear of the car sags, or if you use a spacer on a spring with a known short free length.

Hope this helps, Jim