Greetings! I have a 1987 190e 2.3-16 5 spd that I recently purchased that I am trying to become familiar with (the Merecedes service manual is en-route!).
This is probably a stupid question but this is my first Mercedes & my first experience with this type of suspension. (Not to mention my first time on a forum)

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The car sags in the back end. When I purchased it about 3 months ago, the tires were good all around. Now my back right rear is completely bald & the driver's side is well on it's way. Fronts are good. What could possibly cause this? Can it possibly be related to the sag in the back end?
I suspect there's more to it after reading through this forum but need some sort of direction.
I appreciate any input!