Strange Observation

[hauser]

There has been something that has bothered me for quite a while.  I don't know if this is just part of the beast or if there is something not properly aligned.  I am refering to the rear wheels.  I have observed that the right rear wheel is out farther than the left rear wheel.

  At first glance I thought it was just an illusion until I measured it.  I used a 4-5' string with a metal washer attatched to its end.  I then draped it over the center of the fender until it was next to the lower sidewall.  I repeated this on the other side of the car.  And there was about a 1/2" difference.

I needed to know if there was something irregular with the body work and measured from the center anchor of the soft top to the edge of the fender edge and it was fine.  I made sure the car was flat and level and both tires were inflated to the same pressure. I stil was not satisfied and removed the hubcaps and took measurements from the center of each wheel.

I would like to know if there are other members who have this same irregularity.  I have tried to make some observations from various pics I have but am unable to come to any conclusions.

Perhaps a few members could try this same experiment on their cars and we could compare our findngs.

1969 280sl 5 spd        1999 ML320          Gainesville,Fl.

[A Dalton]

The rear axle has to be centralized via the cross strut adjuster link.
 The spec is 36mm- +/- 2mm. off-set from the center of the pivot pin , to the right of the chassis centre line.
 Look in  the archieves , I have posted several articles about it along with an inexpensive homemade tool to ease the job..
 It has always surprised me that many align these swing axles without any  regards to this measurement. It is the first measure that should be set before any others, as the car steers from the rear wheels
along with the other measures are takern from the rear axles geometric
positioning to the chassis lontitudal axis....
 For those w/121 chassis , this spec is 42mm...+/- 2mm

[rwmastel]

quote:Originally posted by A Dalton

The rear axle has to be centralized via the cross strut adjuster link. The spec is 42mm- +/- 2mm. off-set from the center of the pivot pin , to the right of the chassis centre line.

So, does that mean the whole axle is off-set 42mm (almost 2 inches) to the right?  That is, my right rear wheel should be sticking out from under the fender?  I must be misunderstanding you.

quote:Originally posted by A Dalton

.... as the car steers from the rear wheels ....

That's odd.  Mine steers when I turn the front wheels!  

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

[A Dalton]

<<<I must be misunderstanding you>>

 I believe you  don't understand the geometric layout of the 113 chassis ..
 The pivot pin of the differential has to be offset to the right of the chassis center line IN ORDER for the axle to be perfectly centered with the chassis.
 The reason for this is because the pivot pin is NOT in the center of the axle....it is 36mm OFF the center...so...you place it at the Factory spec of 36mm offset from chassis center..again, this is accomplished by adjusting the cross strut length. That is why the cross strut has an adjustment feature..When you finally have the pivot pin center the spec distance of 36mm to the right of the chassis center-line, you have a 113 with the rear differential perfectly centered with the cars chassis..
 It is all in the chassis measurements/specs layout .

 Forget the steer ,rear wheel physics..it's an alignment thing

[A Dalton]

ET al,
 The correct off-set spec for 113 chassis is 36mm, +/-2mm off-set.
 The 121 chassis would be the 42mm..

 Previous post have been editted for this spec. typo correction.

[TheEngineer]

I replaced my rear axle with a 3.27 from a sedan. The BBB has instructions how to measure for centering. I found that no adjustment was necessary. My wheels are centered. A good visual check is to sight along the rubber strips just forward of the rear wheels: The point of the star of the Mercedes emblem of the wheel covers should be in-line (vehicle unloaded, tank 1/3 full)

1969 280SL,Signal Red, A/T, P/S, A/C, Both tops.    Ret. engr. 1967 230SL - Sold