Stock Rear Spring Decision

[n/a]

I've searched bulletin boards and forums 'till the cows came home', and I am resigned to being unsure about whether to progress or regress. So, by default, I will seek stock replacements.

Where would any of you suggest these be purchased, most economically?

PS: I've also searched the words "compensating spring", and have found no description/information on their purpose. What do they do, and how does one know if it needs replacement?

Thanks in advance for your kind reply(s)


Not so Nervious (anymore) Newbie `68 280sl

[Cees Klumper]

For new stock springs I would turn to the regular parts vendors and compare their offerings. I am not sure whether there are aftermarket versions out there or whether everything is Mercedes-Benz 'sanctioned' supply. I would be interested to know why you would not opt for the progressive springs, because at least in my experience, they do add to the handling and don't take away from the comfort. Anyway, I have not come across a way to determine whether any (including the rear compensating) spring is worn or not. I suppose I will get around to replacing mine at some point, because I have no idea whether they were ever replaced or not, and I guess 35 years is a long time for springs to last. Not sure about the exact function of the compensating spring, but there has to be one!

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[rwmastel]

Brian,
Why would you only replace the rear springs?  How can you tell they are bad?  Just curious.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

Thanks, Rodd, for asking.

You see, the rear sits about 1" (2.5cm) lower than the front. The front appears "about right" from pics I've seen, and is about 26.25" from ground to the outer lip on the wheelwell.

It's possible that the front is just too high, since I dont have the specs, BUT when viewed from the rear, there appears to be some slight but disearnable negative camber on the rear wheels... as if I were carring something heavy in the trunk.

The ride feels a tad harsh to me when crossing over some of the more pronounced expansion joints. Depending on the attitude of the car and/or its acceleration, I occassionally get lateral wheel hop. These latter experiences may be due to worn shocks, spring pads, the differential mount, or the compensating spring... which is what I was pursuing in previous posts.

So, having said all that, proper Ride Height and Ride Comfort (vs. Handling) are my objectives, and why I'm thinking stock rear spring replacement.

Is this faulty thinking?


Not so Nervious (anymore) Newbie `68 280sl

[jeffc280sl]

Hello Brian,

I recently replaced all 5 coil springs with progressive springs.  I like the performance very much.  You can read my other posts for more details.  

Now to the matter of ride height.  Overall I think it's a subjective thing for each driver.  Prior to the spring change my car also sat lower in the rear.  I didn't care for it. I also had some negative camber in the rear wheels (bottom edge of tire was out further than the top edge). Both lower spring pads were in tatters. That could account for a small lowering of rear height but not much. The top pads were somewhat compressed but in overall good shape because they are out of the weather in their location.  I would check the lower coil and compensating spring pads and assuming you have some negative camber, then consider changing out the top spring pad for a thicker one.  As you may know they come in 3 thicknesses.  Springs and spring pads were matched in the factory to determine the car height.  I believe they vary from one production run of springs to the next. Thicker pads will take care of the camber and ride height problems.  There cheap and relatively easy to change.

Good luck,

Jeff
1970 280SL 4 speed

[George Davis]

Shoot, I was hoping a suspension expert would jump in and really explain how the compensating spring works.  It appears to be part of an axle design that minimizes the excessive camber changes that occurred with the original not-low-pivot swing axle design, as used in the Gullwings.  I've puzzled over it a lot and still it makes little sense to me.  But I can say this: it does not serve to laterally locate the axle.

Lateral location is done by means of a diagonal cross-strut that attaches at the front of the axle pivot on one end and the body on the other.  Hard to see unless you get right under it.

Because of the swing-axle design, ride height and rear camber are inseparable: raising or lowering changes the camber.  In my view, you set the rear camber to the correct spec... and that sets your ride height.  If the front is then high or low, adjust the front.  Rear camber specs (I don't have the book in front of me) are something like very slight negative camber with a specific load in the car and the hardtop mounted, and very slightly positive with the same load and hardtop off.  In short, pretty much zero camber.

There is a lot of rubber in the suspension.  Before replacing springs, I'd go after all those bushings; replacing them quiets things up quite a bit.  Don't forget the front subframe mounts, lots of fun to change them!



George Davis
'69 280 SL Euro manual

[n/a]

Thanks, Rodd, for questioning my rationale on the spring change. :?

Further investigation of the car and various literature has illuminated the problem... I'm MISSING the lower mount rubbers[:0]

The springs are simply nested on the lower perch/retainer! How bizzare that the P.O. would have left them off?!?

I went to K&K (a pleasant surprise to find them in "my own back yard")and they had the mount rubbers in stock. They are a bit more than 1" tall, which is just about how much too low the rear sits.

I could get off cheap with this one, since the mounts are only $10 each... alot cheaper than new springs huh.

George, I hope we get an "official" answer re: the compensating spring someday.

`68 280sl
`62 Lincoln Continental Conv.
`73 450sl

[rwmastel]

Brian (and others),

Are these the pads that are available in different thicknesses?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

Nope.

The three thickness pads are at the Top. The line drawings/part drawings I've seen also show a single thickness pad at the bottom.

I suppose this makes sense. Most other coil spring set-ups I now recall have a pad top AND bottom, though none quite as thick.

I imagine some improvement in ride comfort using the ole seat-o-meter.



`68 280sl
`62 Lincoln Continental Conv.
`73 450sl

[rwmastel]

Brian - That's good news.  Let us know what kind of difference the $20 fix makes.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

As often the case, the prospect of a $20 fix was too good to be true.

Turns out the bottom pad IS NOT 1" tall, the difference between front & rear of car I'm trying to correct. The parts house measured the wrong part for me over the phone... instead measuring one of the top pads with a similar part number.

Back to squre one... replace the springs.

With current springs now out of car, I'm now wondering if they are the orginals or close. They have paint markings... three red marks near the bottom, and four yellow markings followed by two beige/white markings near the top.

Does this sound like OEM markings? Anybody know what they mean?

`68 280sl
`62 Lincoln Continental Conv.
`73 450sl

[n/a]

Thought I would close the loop on this project.

Based on the paint stipes/markings on my rear coils, the perch was suppose to be in position #3 (the numbers are stamped into the perch plate), rather than in position #2 as I had received the car. Also, the BBB indicates the rubber pad for a coil with 3 red stripes is suppose to be the 20mm version rather than the 14mm version that was installed.

Since the coils "looked" fairly fresh, I corrected the perch position, replaced the top pad with the thicker version, and replaced the Bilstien's with a new stiffer pair.

Ride height and quality seem to be nicely restored.

I had already purchased replacement springs (not returnable), so if someone out there needs an unused pair (single blue stripe) at discount let me know.

Cheers


`68 280sl
`62 Lincoln Continental Conv.
`73 450sl