My question is whether to replace them proactively or leave them alone. I expect that the answers may be based on opinion.

I never had a failed "bounce" test​ in my 30+ years of owning (well-worn) cars, but a recent strut replacement in another vehicle improved ride quality.

Why am I asking? I don't have any reference to tell if ride quality had deteriorated due to miles/age.

I got my 2010 E350 base sedan (RWD, no fancy suspension, 110,000 miles) several months ago - my first Mercedes. Nothing in the suspension is making noise and the tires are wearing evenly. I can get all four corners replaced (Sachs/RockAuto, mounts/bearings/roll-bar end links/ bumpers/bellows) for $640 in parts. I have the tools and a hookup for free alignments.

I recently replaced all four shocks/struts on my owned-since-new 17yo 125,000-mile Toyota and the ride quality improved greatly. Ride quality had deteriorated over time. I replaced all four corners for only $350 in parts - and that wasn't picking out the cheapest RockAuto parts.

So leave it as "good enough" or proactively replace due to age/miles?

 

toyota mostly uses cheap KYB struts that last 50K-80K miles. Mercedes uses Sachs struts that last many many miles and years

 

Depends if you're having issues or not. I replaced the rear shocks and springs when I noticed cupping on my back tires. I did the front springs/struts when one side looked a little lower than the other and the car isn't lowered. They used to say replace them at 50-60k and mine were in the 100k range so I figured it was time anyway. Used factory springs on the front and when you looked at them next to each other out of the car, they were the same height, but after putting the new ones in, the height of the car went back up. I think the people who get away with not replacing them must live on the west coast with smooth roads and no potholes. Springs and struts get plenty of use here with the bad roads and potholes.

 

True. In another thread you mentioned struts working well after 200k miles. How did you determine that?

Internet searches only yield confusion. Places that make money on replacement say 50k-100k. Others describe a bounce test that, for me, has never been conclusive.

After replacing struts/shocks on my Toyota (17y, 125k mi), BMW (20y, 60k mi), and Dodges (any years, any miles, lolz) - I expect that the bumpers, bellows, and bump stops are deteriorated due to age alone.

 

yeah, how much rebound after going over a dip/bump in the road is my ultimate test.

 

Bounce test is for a 1968 Caprice.

Modern suspensions have sufficient damping even when a shock is “failed”, from bushings, ball joints and residual damping in the failed shock, for example rod seal friction. A hand test will never identify a failed shock on a modern car.

Replace shocks when tire wear tells you to, or when the ride is intolerable.

Reduced jounce control over potholes is a good real world test. If normal driving over normal broken concrete at normal speeds is objectionable, replace the shocks.

I ran a Touareg to 238k miles and never changed the shocks. Fronts would have been nice but tires weren’t seeing unusual wear so left the factory shocks as-is.

Aftermarket non-OEM purchased shocks are significantly lower quality than factory branded and sourced ones. If you want new-car ride, buy shocks from the dealer. $$$ And replace control arm bushings and ball joints/tie rod joints.

 

I really appreciate this thread. I ask myself this question all the time. My car has 145k miles on the original suspension. I had an alignment done by the dealer like 10k ago and specifically asked them to check the front end. They said was the normal course of doing an alignment. The car handles well but I don't find the ride quality to be all that great. I can't tell if this is a result of worn suspension parts or if the W212 just doesn't ride all that great. I wish there was a definitive test that could done to clearly identify if the struts and other elements of the suspension need replacing. When I replaced my brakes this summer I tried to wiggle the wheels to identify play in the suspension but didn't see any. The last thing I want to do is buy a bunch of parts and put them on only to find that I really haven't improved things all that much. That said when I redid the struts, shocks and control arms on my wife's Mazda 3 it made it like a new car.

When a modern strut wears if it isn't leaking what components internal to the strut are wearing? Same question on control arms, what is the wear item? What happens to the rubber isolator over time?

 

Did you measure the height of both sides? Basically from the fender to the tire. I could tell just by eyeballing it that one side was a little lower than the other and I measured it to make sure there really was a difference so at that point I replaced both the springs and the struts. The struts aren't that expensive, they're cheapest on Rockauto although they don't have it indexed right, go to Bilstein's website to look up the part number and then look for them on rockauto. Much cheaper than FCPEuro and it already has a lifetime warranty so no need to get it from FCPeuro. Before when hitting certain bumps, the suspension felt flat or dead or felt like it was bottoming out. Afterwards it took the same bumps with no problems and felt solid and bounced right back, didn't have that bottoming out feel anymore. At 145k, there's no way that they're anywhere near to new condition. I wish there was a quickstrut for the car, but with sport and luxury suspensions out there along with 4matic and 3 sets of possible springs, it makes sense that there wouldn't be one. A bit more expensive then than a regular car, but well worth it afterwards, the luxury suspension is much better handling bumps.

 

From my experience , it's about the mileage and the conditions of the roads on which the car is driven . I have not seen a car 50 years old with the original struts either

 

There are 2 simple test you can do, but its more of knowing if the nitrogen gas has leaked out or not or if the valves oil flow value have drifted too much.
The test is simple, but the damper (rear) and the strut (front) has to be removed.

First watch this video on how internally our simple damper is like :

Damper is clean with no oil trace.
A simple push down test and wait for damper piston to rebound back to maximum length is one of the test.
If the nitrogen gas has leaked out, the damper piston will simply stay put and no rebound at all or jerky movement.
Depending on damper design, nitrogen gas can leak and no oil leak trace at the seal, because gas molecule is smaller than liquid oil molecule so gas can leak first instead of together with the oil.
The rebound movement should be nice and smooth. Nitrogen lost will make oil foamy and damper behavior will go bananas when oil/damper is hot.


Next one is crude test but not a bad way to test both LEFT and RIGHT dampers if they are behaving very different compared to one another.
Get a nice digital bathroom scale as measurement device.
Practice how to push down slowly but smooth consistent speed the damper piston, there you will see the KG force needed where the piston starts to sink down when pushed and
KG force remain constant all the way to the bottom of its travel. If BOTH dampers don't come close within like 3-4KG of force, the valves condition on one of the damper
has more leak thru rate.

Next level if you can access the service at low cost and enjoy the learning, get a facility with damper dynometer.

In many cases they may have typical chart for common dampers to compare against.


Where does the wear and tear occurs ? Assume no gas or oil leak.

Zone 1 is the dynamic seal which makes sure oil flow only occurs at Zone 2
Zone 2 is oil flow control vallve compression/rebound










Zone 2 is like a 2 stroke engine reed valve, well sort of in its ways of working by flexing up or down to allow oil to flow.


In most cases dynamic seal of zone 1 will have the highest wear and tear from such long travel.
If this dynamic seal leaks, it wont leak out oil out of the damper, but the oil flow control of zone 2 becomes negatively impacted.
Damper's damping capability is all about oil flow control, so when the oil flow control goes south, damping behavior goes bad too.

Zone 1 dynamic seal is rarely and instantly damage thingy, its slowly progressive leak, more and more pass-thru leak.

Depending on how one's Butt-O-Meter sensitivity, hearing sensitivity and the familiarity with certain reference road bumps and corners at various speed,
most casual drivers can't sense a weakening damper as it is a progressive weakening, unless mechanical condition of the damper is really bad.

I said REFERENCE road bumps. These are bumps we know so well. we can tell rebound difference of the dampers if its is starting to weaken.
The best kind of road bumps to use for reference I like to use are 2 types.

First one is this kind of very polite speed bump Singapore uses. Doing 40KM/H on these speed bump is a comfy affair, it is so well made.



The second version I like using at higher speed like 100KH/H or more are those nice small bridge over a small creek where when we speed fast enough over this mount, the whole car will be
almost off the ground or suspension is like hanging down in air fully uncompressed but tire still touching tarmac, upon full touch down back to tarmac the weight of the car and the
small jump we did is good one to test damper compression & rebound. A bad damper upon full touch down to smooth flat tarmac may do 2 to 3 compress-rebound cycle,
a good one can do a clean 1 compress rebound cycle. I hope my explanation is good enough
Here explains the force of rebound



REFERENCE corners
A nice tight corner will cause weight shift to one side of the car, this is to test damper compression speed consistency.
Our damper is a speed device, the faster we compressed the more KG force needed. It is basically hydraulic principle, deliver more liquid and faster to a same size opening/orifice,
HEAD resistance goes up.
When one take the same corner hundreds of time at similar dry condition, at similar speed, one will be able to sense if damper or tire pressure is not correct.

A tight/short S bend is also good to test damper compression and rebound for Left and Right dampers as the weight shifts can be made very fast with faster vehicle speed.
Weight shift will push and lift suspension system. Here heavier car gets penalized, no choice.

Have fun experimenting................

 

Hello, first time here but thought I'll share my experience on the subject.
The front struts on my w212 E300 have been replaced at 110k km, now at 190k km they are a bit leaky again. Shop told its not a major leak but something I should consider replacing in the near future.
So I'm looking into replacing the fronts with the original rears + replace the full original front suspension components.
The car is daily driven on bad hot high speed highways all its life to give some reference. Current ride quality doesn't feel that great.

 

But there are plenty of 1980's MB still driven in California on original struts.
When I never replaced 1 on MB, even I had several of them with high-mileage, I still remember test I did on Fiats.
Push the corner down with your body weight and let it go. Good shock will just pop up and stop. Bad shock will bounce.
My Ford has no struts at all....

 

Ride comfort = tires + ball joints + tie rod joints + control arm bushings + shocks.

*above assumes springs have not failed

Like-new ride comfort means all of the above must be new or nearly new with OEM quality parts. MB control arm bushings are known to fail. There is no definitive test for modern shocks. If the ride feels like crap, and you want to spend the money, replace the shocks.

No wiggling will find loose wheel bearings. Ball joints and wheel bearings would have to be so far gone the car would be obviously unsafe to drive, if hand wiggling showed anything.

A suspension corner (wheel) has 1,000lbs or more weight on it, and any trivial effort a human can exert is nothing relative to the weight already on the components.

 

Fun fact: I have yet to replace the rear shocks on ANY W212 E Class despite me trying to find dead ones for a year in business now. The W212's due to their age are the #1 cars I see as the C are too roached out to care about due to the typical 2ndhand owners, and the S is there, but more people buy the GL/GLS for the money.

The fronts, sure, especially the airmatic units at around 120k, but thats very reasonable given what they do.

You can go broke trying to find intervals for Mercedes stuff. I'm running the original water pump at 143k on an E550 and I literally have a new radiator and Graf pump stored away for over a year in case I wanna do some gnarly cross-country trip or something but at this point I'm curious to see how long the original goes. When I did all of my front control arms the cracks would only appear if you REALLY went at it with a prybar, and I did not notice a single improvement in handling or steering. FCPEuro's Youtube videos really convince people their cars are more broken than they are. For me the things Mercedes really need interval-wise are the fluids. Transmission SHOULD be done every 30, DOT4 annually, and oil at 7500. I will say that the gear oil on non LSD cars seems to still come out clean at 120k+.

 

a historical (hysterical?) case in point... some years back we bought a W124 1994 E320 wagon that had about 220000 miles on it, the front struts were original and very very soft. We replaced them with Bilstein TC ('touring') when we got it, everything else in the front end (and rear) was in fine shape. The hydropneumatic SLS rear leveling system needed a fluid flush, but was otherwise AOK. We put about 60K more miles on that car, and it was sitll driving 100% fine

 

For the record, W124 was still in the era where cars had big body sways. I always have fun observing those 1980's movies, where huge cars dive the nose on each turn.
Sway bars of that era were much smaller than what we can find today as well. Not to mention that the design where sway bars sit on rubber bushings was always neglected in maintenance.

 

Earlier this year I got a squeak like all of my pulleys were going out but it would happen if I closed the door too, it was just the vibration of the engine against the worn sway bar bushings, there had been a gap that formed in them due to the rubber cracking.

 

Internal components fail such as the damping piston valve discs and base valve or floating valve discs. The discs are tiny thin sheet metal parts and crack with fatigue. The rod seal often does not fail. A “failed” shock retains some damping nevertheless.

Control arm failure points are ball joints and rubber bushings. Nothing made from rubber has an infinite life and furthermore can take on a set after years of weight on it. MB and other higher end cars often have fluid-filled soft rubber compound bushings in the front lower control arm, for comfort. Similar principal as fluid filled engine mounts. Fluid filled and soft rubber = shorter lifespan than harder rubber and not fluid filled.

Stabilizer system failure points are drop link bushings or joints, and stabilizer bar bushings.

 

So I should clarify my objections to the suspension performance. In general the highway ride is great. Low speed on the crappy streets in my neighborhood isn't great not harsh but impact is sharper than one would expect for a luxury version of the W212.

The biggest suspension issue I have is with the steering feel on the highway. It is lacking in isolation from vibration and road imperfections. Perhaps I have euphoric recall but I don't remember any of this crap in the steering on my small wheel, recirculating ball cars (220SE's and 190E) .

I have good Michelins that I have had balanced at Costco. The steering is rarely smooth and vibration free. Since my car sits for a week at a time I often have to work through flat spotting on the tires on a given trip.

First and foremost is the steering on your W212 luxuriously smooth on the highway?

Can strut or other suspension wear drive this lack of steering smoothness? I often imagine that it could if the low amplitude portion of the agility suspension shock is failing or the control arm bushings are soft. Does this make sense?

Despite the fact that I have had them balanced would road force balancing the tires correct this?

 

thats inherent in the stiff short suspension with very low profile tires ... you either have 245/45r17 or 245/40r18, both have very very short sidewalls, and teh whole car on short stiff springs compared with cars of 30 years ago.

1994 E320 wagon, sitting on 195/65R15 Michelins...


2016 E350 wagon sitting on 245/45R17's...

 

My family's 21 year-old C320 with 165,000 miles currently passes all the tests shown by S-Prihadi in post #10.

The roads here in Texas are not perfect, but better than in Pennsylvania.

I'm not anticipating replacing the shocks in my W212 (39K miles) any time soon.

 

This reply is entirely consistent with what my service advisor said when I complained about the same on my W211 which only had 30K miles on it when I bought it. At the time in my mind I was blaming the rack and pinion steering vs the old recirculation ball.

So is it fair to say that you get a lot more road feedback and vibration through the steering wheel on your W212 than you do (did) on your W124?

If so it would close this issue out for me.

 

Yes, the 124s were plush.

 

Can't thank you enough for your replies. Those cars spoiled me. When I was in college I had a '59 220SE. That car was as smooth as a modern electric car. You stepped on the gas and the only thing that happened was that it went faster.
You couldn't even hear or feel it idle. After spending a day driving D9's in the S.J. valley I would get in it and couldn't tell if it was running.

 

Modern tech is great ....