Bad shock?

[JHZR2]

Please note dirt pattern:

Versus other side:

Where you can see the consistency of dirt.

Both tires are at 36 psi on rear wheels of 82 mb 300cd. Both were on the front until about 700 miles ago, and I did have a bad lca bushing before that which caused some funny wear.

Thoughts?

 

[Steve S]

Independent rear suspension it seems? If you push down on the rear end what does it do?

 

[PandaBear]

The bottom pic looks normal except need to rotate the tire (saw tooth wear)

The top looks like minor amount of shock/strut wear, if you keep rotating tires every 5k it shouldn't be a problem.

Dunlop SPA2 huh? Mine wears about the same as your top pic, regular rotation and they seems to stabilize and not getting worse.

 

[Trav]

Is there any cupping?Did you check the rear control arms?

 

[RH+G]

Alignment is off

 

[Trav]

The reason i ask about the rear control arms is they are known for rusting out on these models especially in the salt belt.

 

[JHZR2]

The control arms look like new, the car has lived in CA until last Nov. Every piece of metal looks like it came off the factory.

That doesnt mean that the bushings are OK. Ill have to look.

The tread was abnormally worn because those SP A2 tires do wear a bit fast on that tread block as was mentioned above (Ive seen the same on other cars where Ive used these tires), and because the alignment was off a bit on the front, which Ive fixed (and was the reason why I aligned it last). I think it was a bit cupped when on the front, but the dirt pattern on the tread did NOT look like this. The tread looked like the whole tire contacted the road at the same time, just it wore faster in some spots. Now it looks like parts of the tire dont even touch.

However, I would think that after 700+ miles, the dirt profile would be more consistent, since being on the rear. I kind of recall that bad shocks can cause abnormal wear patterns. That is why I ask.

On small imperfections, I sometimes feel like the rear bounces around. On big ones it is solid, just a bounce, nothing excessive.

Pressing the rear doesnt yield abnormal shaking, just a bounce.

But that doesnt mean it is dampening properly, right?

Thanks!

 

[mcrn]

JHZR2 I used to have an 83 240D and I had bilsteins put on all 4 and that thing was rock steady. Never any bouncing, I mean not even close. It was just a well dampened controlled ride. I got to drive it a year after I sold it and I remember thinking I can't believe how good this car handled and was such a well controlled ride. I was more amazed then because I was not used to that car anymore. I was driving a 96 Ford Ranger at that point. But that Benz was so solid and it was almost 30yrs old! No rattles at all! Great car except that Vacuum system! Hated that part. So anyways maybe it is the shocks? I highly recommend Bilsteins for it! My dad had an 82 300TD and my mom had an 80 300SD. Bilsteins did great on all 3 cars and still felt like new after we put over 100k miles on them.

 

[JHZR2]

I have a 240D with only 73k on it... great car. The one in this case is my 82 300cd, with 161k on original shocks (bilstein or sachs most likely). I dont mind replacing all of them if it would help with this wear. The car does drive very solid, I just drove it 500 miles over the last two days and it has been great.

 

[Trav]

I would put rear shocks in this car, you are correct that shocks can cause strange tire wear.
It can be difficult to tell the condition of the shocks by bouncing the corner these days.

Unlike the old days when shocks were basically valved very simply, compression and rebound were pretty much 50/50 so bouncing the corner down would give a fair indication of the overall condition of the shocks.

Today valving is much more complex, most modern designs use variable valving to smooth the ride over small bumps and stiffen when a greater impact is received in an effort to keep the suspension of the bump stops.
The shocks rebound capability could be diminished without having much of an effect on the compression stroke with these complex valves. Unfortunately the old bounce test does not give a total indicator of the shocks rebound capabilities when subjected to different impact levels. This could cause tire wear while still seemingly providing a seemingly decent ride. MB used fairly modern shock technology back your car was built.

One other point about shocks..
If a gas is used to prevent oil foaming it can be lost sometimes without also showing oil loss.
This would have no apparent effect on the shocks performance until the fluid heated and began to foam. Once cooled the shock would perform normally, this would be undetectable with any test except for a machine that bounced the shock over a period of time to heat the unit by simulating road conditions. I see these machines often in Europe but not here in the U.S.

Before doing the shocks check the control arm bushings and any sway bar components.
Also check sub frame mountings for worn bushings going into the body if used in this model. Rear sub frame shift was very common on some BMW models because the large bushings going up into the body would wear allowing the sub frame to shift slightly.
I believe the rear sub frame front mounts are similar on this MB. These bushings if worn could cause the tire wear pattern shown in the pictures.
The sub frame does not need to be removed if they are gone, just lowered but some big washer and threaded rod will be needed to fabricate a removal tool. Use rubber lube or dish soap not grease.

 

[mechtech2]

Bad shocks don't cause cupping at 1 inch intervals perfectly even.
This is probably from being on the front with previous problems.
700 miles is usually enough to let a tire settle into it's corner after rotating, but give it some more time.

36 is OK, but a maybe little high .