Hello all,

I've got the front shocks and rear shock bushings replaced; but under certain road imperfections, my car feels like the tires are over inflated too much - even though it's only 29/30psi front/rear on CH95 Continentals. Anyone else experience this or have any inputs as what to check for ?

Thanks in advance!
Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

A VERY common problem in the 560SEL is failure of the rear nitrogen-filled accumulators, which I believe are part of the rear shock system. When they go bad, you get a very rough ride.

These fail so frequently that from what I've read, if a 560SEL has ride problems and the accumulators haven't been replaced, that's the first thing many folks do.

If you do a search there are likely to be more posts on this. I believe this is a reasonable DIY project.

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Steve
'93 400E

Steve,

I could feel the bumps on the steering wheel; so front suspension is also a suspect here (steering coupling still looks fine though). The rear is a lot more comfortable ever since I replaced the upper shock bushings but I still feel like it has >40psi on the tires.

Would subframe mounts (fr & rr) contribute to this ? I believe these are originals (now at 192Kmiles).

Regards,
Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

back to top...

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

Have you checked your accumulators? There cheap and if they went bad your hurting $490 shocks!

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Are you running the OE 205/65R-15 size? If not, what size?

Duke

The tires are OEM size. The accumulators appears to be old (originals I guess) but still functioning. It's just the feel on some road conditions that's almost like the tires' pressure is too high.

Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

Well, if the accumulators are in fact original then they are probably shot. If they are shot the back end will ride like a log wagon because you have no shock absorption ability. If the back end is riding like a log wagon the front end will probably be handling a little squirrley in response.

You also listed in your original post that the shock bushings and bump stops have been replaced on the rear struts. As I understand riding around on a set of dead accumulators plays hell on the shock bushings and bump stops because those two little pieces of rubber are the only cushion you have.

Might be worth taking a quick look at the condition of the fluid at the leveling valve. There is a bleeder screw screw there, put the car on ramps keep your extremeties out of harms way, attach a clear tube to the bleeder and crack it. Let us know what the fluid looks like coming out. Does it look a little like sea foam?

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

I am also running CH95s, and overall am very happy with them, except - sometimes I feel like they have too much air in them, even though they are inflated to a "reasonable" 35psi (considering they are rated at 51psi).

Mine are oversize (235/50-18 front, 265/45-18 rear) on a 92 500sel, but I find the same symptom that you do. I have also replaced all required bushings, etc.

It is a "shudder" (where the tires seem to "pound" the suspension), and I was thinking that there is some other worn suspension component that I have missed replacing, but maybe it is just the nature of these tires (where they have a sharp threshold between the normal "soft" ride, and a much sharper ride when negotiating a bump).

Just my thoughts - if my car were new, then I would be more confident that it is the tires and not some other suspension item.

-David
92 500sel (not for sale)
86 560sel (sold last week! finally gone!)
85 535i (to be sold this week)
82 QPorte (would be sold, but no one will buy it...)

Shorter sidewall tires will usually increase ride harshness. The bushings on the 560s are tuned for the relatively flexible sidewalls of the 65 series tires that will damp out most of the high frequency road input.

I recall riding in the back of a friend's 560SEL some years ago - OE size tires - and was suprised at the ride harshness. The damping felt okay, but you could feel/hear every thump in the road. It was like the rear of the car was riding on wooden wheels! I guessed it was somewhat attributable to the semi-traling arm rear suspension on the 126s. The multilinks in the 201s and 124s certainly don't transmit anywhere near that kind of harshness.

Duke

The nitrogen sphere accumulators lose their charge over time. Since there isnt hardly any nitrogen left in them there is no gaseous component to the hydrostruts. The only thing that is in the hydrostruts is the hydraulic fluid. Since fluid doesnt compress there is no damping/shock effect to them anymore. Hence, the feeling of every bump and also the feel of too much air in the tires.

Take a look at the hydrostruts also. You shouldn't see any fluid around them. They should be bone dry. The hyrdostruts are very expensive. They cost in the neighborhood of $600-$800 to have one replaced.

Good luck,

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Frank
84 500SEL EURO 101K ( JUST LIKE MY 1ST WIFE. GLAD TO GET RID OF HER! )
85 300D 310K (sold)
90 350SDL 184K sold
83 300D 118K (sold)
88 300E 153k (sold)
93 400E 105K (sold)

Frank,

Have you checked the tire pressure with more than one gauge?

Peter

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Auto Zentral Ltd.

I did a rear suspension test; it compresses and rebounds fine at idle. All components are bone dry - no leakage whatsoever. However, it does not seem to level with heavy load so maybe it's time for new accumulators (even though moving the leveling valve arm manually would raise the rear up). The arm at idle, and no load, lies horizontally on flat ground - is that a correct setup ?

Peter,

My compressor gauge and the digital gauge tend to agree on the pressure besides, it feels very nice on rough road at slow speeds so I'd rule out the tire pressure issue.

Regards,
Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

Frank,

Just checking, because it happened to me once. I had a pressure gauge off by several pounds which cost me a new set of tires for a client. Bill was a noble man and a rare breed. He only asked for a prorata share since he had gotten use from the tires. Back to the original problem, I'm having a hard time condemning the nitrogen cells, because they usually produce a bouncy back end. Since the rear suspension on an MB load leveling system has no shocks, The shock action is relegated to two spheres. A sphere on each side of the car has a thick rubber diaphragm in the middle. On one side of the diaphragm is nitrogen, and on the other side is hydraulic fluid. When you hit a bump the hydraulic fluid tries to take the space of the nitrogen. The nitrogen being compressible gives a little and takes the bump. Perhaps you have some nitrogen left and haven't reached the bouncy stage. Hope this explaination helps.

Peter

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Auto Zentral Ltd.

Steve,

It is the nitrogen that acts as a shock absorber. Once the hydraulic enters the other side of the diaphragm, it is all over. Remember, hydraulic fluid doesn't compress.

Peter

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Auto Zentral Ltd.