picture of undercarriage of 1967 250s

[250sVegas1]

does anyone have some good pics of the undercarriage of a 108? I havent seen one yet. I was wondering what the thing looks like from underneath

[jaimekop]

Is this useful?

http://images.jaimekop.com/2002_05_27_250S_Rear_Suspension/pages/IMG_2617.htm

Jaime
-many 250Ss in the past

[wbain5280]

Nice pic, you're missing a rubber ring for your exhaust.

[jaimekop]

Ha, yeah, it was missing... that was back in 2002! Sometime in 2005 or so the exhaust had rotted enough that it had to be replaced... the car got a timevalve stainless system.

Jaime

[250sVegas1]

thanks guys...I was hoping that I could get a pic of the front as well. I wanted to see the tranny and the flexdisk assembly . thanks a million for the pic really helps me to see the guts of the beautiful 108. more pics would be great Hey Jamie, you working on any new projects?

[jaimekop]

Hm... I don't think i have too many front end pics... I was lucky enough to not have to do much work there.

No cool projects right now... I'm kinda starving for one. The moment that 250S (or 250SE) with a sunroof, ac, and a 4 speed shows up... I'm ready! :-)

Jaime

[JimFreeh]

Originally Posted by jaimekop

The moment that 250S (or 250SE) with a sunroof, ac, and a 4 speed shows up... I'm ready! :-)

Jaime

Jaime,

I had a 250SE equipped like that back in 1975. Black with tan 'tex.

I loved that car, except for one thing; it did not have power steering. Man, was that car a bear to parallel park!

I'd own one again today, if I found one....

Jim

[JMela]

Did you notice any big differences with the timevalve system? Did timevalve have a model-specific kit or did you modify one of their existing systems?

[jaimekop]

The timevalve system was pretty good, and I thought it was appropriate for a car that would be driven a small number of miles over a long period of time. I would use them again. The fit was pretty good... I've used them for other cars ('85 380SL and '80 280SE) where there were minor problems. Its hard to bend the stainless pipes, especially when there are two run in parallel.

Jaime

[todds]

Hi Jamie,

I wanted to thank you for the excellent Zenith resource which I constantly refer to. I have a question, when you rebuilt the rear susp, did you follow this guide which I read once on the mbz.org list? I always wondered how relative it is.

"My two cents on the rubber carrier bushing for the rear axle (of the swing axle variety).

The correct installation of this bushing is paramount to the ride quality of the rear of the car. If you've already done everything and you're still not impressed with the ride of the rear (it's too harsh over bumps and you notice every little undulation in the road), chances are that the alignment between the carrier arm and differential are incorrect.

The chances of this bushing having been replaced over the years (probably a couple of times) are excellent, and the chances of it having been done correctly are slim. Without going into all the technical details, suffice it to say that unless the centerline of the swingarm hinge pin is absolutely parallel to the horizontal line of the vehicle, the axles cannot swing freely through their arc. The further the centerline of the hinge pin is from its correct position, the less capable the suspension is of absorbing road irregularities, and therefore, the worse the ride.

These rubber bushings are a fair amount of work to install correctly, and I'm sure that this accounts for most of the problem. However, there are profesional mechanics out there that don't understand the goal either.

Several years ago I decided to rebuild the rear axle of my 300SEL 3.5. I did everything myself, including installing and aligning the carrier bushing. Once completely back together, I took the car down to the Benz garage to have the side-to-side alignment of the rear axle set (they have the alignment bar and I don't). Well, they decided to do me a favor and realign the pinion angle as well, since it "wasn't pointing in the right direction" (this is controlled by the alignment of the carrier bushing). I had spent a great deal of time and effort to get the carrier arm position exactly right while the rear axle was out of the car and these guys had screwed it up. (In their opinion, the pinion was supposed to point directly at the back of the transmission.)

Well, I made the mechanic ride in the back of the car for a few miles, just to make sure he knew what it felt like. Then I made them pull the rear axle out of the car and realign the carrier arm on the bushing per factory instructions. They then put the rear axle back in the car. (The agreement was that if it improved the ride, they would eat the labor costs, and if it didn't improve the ride, then I would pay the labor costs.)

The same mechanic spent a few more miles on the backseat, and willingly stated that he hadn't been in a 109 with such a good ride in 20 years. They ate the labor costs.

There is more going on in the mechanics of the Benz swing axle design than readily meets the eye. Study it and ponder why it is designed the way that it is. Then FOLLOW the factory proceedure for replacing the carrier bushing.

Watch out for this! This really is one of those jobs where if you're not going to do it right, there is no point in doing it at all.

Chris Johnson"

[wbain5280]

Todd, that for that excellent writeup. I agree that the shop screwed up, the later cars with the body mounted diff had to be aligned to the trans, assuming good engine, trans and center mounts. The swing axle cars have a U-joint and a sliding joint to compensate for the differential movement while that side moves up and down.

[mercmad6.3]

Chris is famous for wanting everything exactly right.
have a look at his site sometime.
www.300SE.org

[jaimekop]

Yeah, Chris has an excellent write up there... it was enough to scare me then, and still scares me today :-). I didn't change all the rear end parts when I did the job, and this write up was one of the reasons! Since then I've become a bit more brave in my repairs, and I found a excellent European alignment shop, so maybe next time I'll give it a shot.

In had replaced the bushings on both ends of the trailing arms, and installed a good hydrocompensator (to replace a spring). The improvement in ride and handling was dramatic. I still have the long tube bushing and diff->body mount somewhere in storage for another day.

Jaime

[todds]

Interesting, what did you need to make the hydrocompensator work? Doesn't it have a pump and hose getup of some kind? I'd also assume that different (vertical) spring rates were used in the rear end of those cars to allow the compensator to do more of the leveling work and give a different ride.

For posterity's sake I might as well post the rest of Chris' admittedly scary writeup:

"The alignment I am referring to is the angle of the swing axle hinge pin in the vertical plane. Since the pinion shaft and hinge pin are forced to swing in the vertical plane together, a change in the angle of the hinge pin implies an identical change in the angle of the pinion shaft. This angle is changed by sliding the carrier arm either in or out on the rubber carrier bushing's outer sleeve. The further out the carrier arm is away from the axle assembly, the more "up" attitude the hinge pin and pinion shaft will have. The further the carrier arm is in towards the axle assembly, the more "down" attitude the hinge pin and pinion shaft will have.

The ideal situation is when the carrier arm is positioned such that the center line of the hinge pin would pass through the inner end of the radius of the arc that the rear axle trailing arms would move through while the car's suspension is in it's "steady" state (neither compressed or extended.) (This is a fancy way of saying that the center line of the hinge pin is parallel to the center line of the car, assuming that the ride height of the car is correct.)

Think about what has to happen when the rear suspension is compressed or extended. The outer ends of the axle tubes HAVE to swing through the arc dictated by the trailing arms, but the relative height of the hinge pin is held constant (almost). This means that not only are the ends of the axle tubes swinging up and down, but must also swing FORWARD to follow the arc of the trailing arms. In order for the axle tubes to swing forward, the angle of the hinge pin must also change. When the suspension is compressed, the hinge pin is forced to point down in the front. When the suspension is extended, the hinge pin is forced to point up in the front.

The problem comes about when the center line of the hinge pin does not intersect the inner end of the radius of the arc that would be followed by the trailing arms. Said another way, the center line of the hinge pin is not perpendicular to the tangent of the arc. In this case, before the suspension can be extended or compressed, the attitude of the rear axle must be forced to rotate into a position where the centerline of the hinge pin is nearly correct, or the axle tubes will not swing. In other words, the misalignment tries to get the axle tubes to rotate around an axis that does not coincide with the physical axis of the hinge pin. Obviously, the axles tubes are going to rotate only around the true physical axis.

It takes a fair amount of force to "auto-rotate" the rear axle into the correct position for suspension deflection, and this force is created at the expense of ride quality.

The only reason that the suspension continues to work at all under such mis-alignment conditions is because of the rubber parts between all of the rigid parts.

Chris Johnson"

[jaimekop]

The compensator is a pretty neat device which is totally self contained. When they failed, many cars had them replaced by a spring since it was much cheaper. Conversion back to the compensator is easy... just install!

The later self leveling suspension (first available on the /8 W114 W115 cars I think) had an engine driven hydraulic pump, nitrogen spheres, etc. This system is found commonly on wagons (123, 124, 210, etc), 6.9s, and option on several other models.

Jaime