How do coil springs age?

[Bruno_300TE]

Hi everybody
Car is a 300 TE 1992 with 150'000miles. I did a complete suspension rebuild recently - except: springs. So I wonder whether I should replace them as well given they do not cost a fortune. How do they age? Besides loosing compression capability do they change shape? Will I feel a difference in ride quality with new springs?
Thanks, Bruno

[samiam4]

A properly designed and manufactured springs have an infinite life.

That being said.. some times they are NOT made correctly or fail due to enviromental reasons. Generally, MB has always been good to me by supplying specific parts data when requested. You could write them and ask them for the free length of a new spring(give them the p/n). Then when you take your old ones out-you've got a way to compare.

My W123 had almost 400,000 miles on it when I sold it. The ride height still looked correct.

Michael

[t walgamuth]

springs last a very long time. changing them is not likely to make a noticalbe diff. and if using aftermarket they might not be as good.

tom w

[Brian Carlton]

I recently went through quite a bit of analysis of the springs on the SDL.

Turns out that the spring rate of the 19 year old springs has not changed at all from the factory.

However, the load height, meaning the height of the spring at a specific length, was reduced by 1/4". This had the effect of lowering the body by about 5/8".

So, on some springs, time does affect the spring and causes it to compress more than the original set from the factory.

However, the spring is still perfectly useable. If I had a thicker spacer available for the vehicle, I would have certainly used it to make up the 1/4". Unfortunately, this vehicle was already using the maximum spacer thickness.

So, I would advise you not to change springs. If the ride height is not to spec, see if you can raise it with a thicker rubber spacer.

In my case, I had new custom springs made that were longer than stock. Now the vehicle sits a bit high. But, I've got two thinner spacers to choose from to lower the height, as required, depending on the look. The SDL changes it's ride height significantly due to fuel and cargo loads. So, setting the height is a bit of a challenge.

[Bruno_300TE]

Many thanks for your insights! I leave the springs alone then and get four (or only three these days...) tanks of gas for the money instead.
Have a nice day, Bruno

[lkchris]

W124 front springs are known to fracture, however.

[samiam4]

If you live in an area close to salt water-

You should install the sacrifical anodes per the MB lit to prevent the springs from breaking.


Michael

[haasman]

Yes some springs do wear over time, especially rear springs. With the many used Mercedes I have owned over the years, I have replaced rear springs on 240D's, 300SDs and a 300E.

It is my experience that Mercedes rear springs are most susceptible. Why? I am unsure but I believe it is related to the rear suspension variable rate springs as opposed to the linear rate front ones. The rear suspensions must endure a greater range of loads and also offer acceptable ride quality and thus their variable rate coils.

With all the cars that needed rear spring replacement, I noticed what I call 'ass sitting". The 380/450 SLs seemed to often have this problem.

Before changing the springs I went through the various spring adjusting collars. Not an easy job for a DIYer in a driveway. Although the collars helped, it was the springs that made all the difference. With 124/201 series, a worn lower spring carrier arm pivot can also contribute to rear suspension settling.

The results of my rear spring changes have always been great. The rear of the cars ended up in the correct rear slightly higher than front attitude and upon acceleration, the rear doesn't squat.

Wagons, with their self-leveling system are a bit different. I have not done a wagon rear springs but it is my understanding that prior to making a spring replacement diagnosis, the self-leveling valve arm must be disconnected.

Haasman

[manny]

haasman

FWIW, I completely agree with you.
Makes me weep everytime I see a 15 - 20 year old M-B with the rearbumper dragging on the ground.
My first thought is " Poor slob can't afford new springs " ( or simply doesn't care how the car handles & looks ).

[Bruno_300TE]

Well, out of curiosity I changed the front springs all the same. And the difference is noticeable: the ride is more comfortable and the steering is more precise, escpecially when cornering. The improvement is not super dramatic but still beyond what I would call a "placebo effect".
Have a nice day, Bruno

[Duke2.6]

The number one killer of springs is corrosion.

Overloading can also cause them to loose some tension, but corrosion remains the biggest threat.

As stated, if old springs still are within reasonable tolerance of free length specification and not severely corroded, they are reuseable.

Spring rate is a function of wire diameter to the fourth power, so it doesn't take much corrosion for them to loose rate, however, serious corrosion is usually not uniform. It tends to create notches, which cause stress concentrations that will eventually cause the spring to break.

At least Mercedes painted their springs, which provided some corrosion protection, at least for a few years. Wish GM did the same.

Duke

[haasman]

Steering and comfort: I should have also mentioned these in the previous post. With the rear ride height corrected, the ass sitter cars no longer felt like boats. They regained their positive steering feeling and the overall ride compliance was great.

Particularly the old 79 240D: For such a small horsepower car, it was a great feeling to not have some of its precious energy consumed sinking into the rear suspension. With the replacement springs (from a used 79 300D) it was a remarkable transformation.

Additionally, there have been several postings regarding changing of shocks and suspension rising from new gas shocks. It seemed to me that just shock replacement in the cars with bad rear springs simply aggravated the problem, probably simply due to weight transfer from front to rear.

Haasman

[Kestas]

I have replaced springs because they've taken a set. The ride height must be checked to determine if they need replacement. When the ride height sags the car can handle squirrely.

[t walgamuth]

over the last 32 years. i cant remember ever changing a spring.

on my 74 240 which had an auxiliary tank put in when new the rear was low on one side and we put in a couple of rubber blocks to raise and level the back, on one side only i think. it corrected the problem and i never noticed any detrimental handling as a result.

and i am pretty picky when it comes to handling.

tom w