they look and feel good. not collapsed much at all. i don't see how these being warn can cause much tire wear on one side.

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

A few things.

The tire is at the end of it's service life regardless of edge wear.

You are running way too low a tire pressure, this will uncover slightly bad alignment far earlier than a properly inflated tire. The outer edge is worn much more than the center.

If a tire starts to wear on one edge then alignment corrected, it will continue it's uneven wear pattern until complete wear out.

The torsion bar, provide the arch in the upper control arm, if its worn it will not provide the necessary tension. It may be the bushings where it pass through the uca are bad or its possible the blot is loose and not correctly torqued. The battery tray area is a known rust area on the w123....its very possible the mount area under the tray is rotted out.

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To answer your question, you cannot adjust toe-in on a single wheel. That doesn't make sense. Toe-in is the distance between the two front wheels, the difference between the aft width and fwd width. By the same token, if you have excessive toe-in, both front tires should wear on the inside edge. I agree it is too much negative camber (tire leaning in at top). The question is how it changed significantly since your recent alignment. Everyone mentioned things that could change the location of the upper ball joint. However, look at the lower control arm too.

If the rubber bushings at the pivot are worn, the pivot point could move outward. If the alignment shop didn't tighten the thru bolt, the adjusting cams (lop-sided washers) could have rotated. Finally, the metal could have cracked at the hole. That as the problem in my 1984 300D when I bought it. The driver's side wheel was leaning in severely at the top, so much that I could barely drive it home (2 miles). The owner assumed the K-frame had cracked again, and thought it fatal. First time it cracked was when the car was stolen and kids drove it into a curb. Actually, the original weld repair was sound and this was a new crack which I fixed fairly easily.

If the alignment was done with a worn out guide rod mount, then you may be chasing your tail, so to speak. Toe in and camber are very inter-related on this car and I don't think any one adjustment is going to bring it back into alignment. How long ago was the alignment? If you talk to the shop, they may cut you a break on the cost since they know that the rest of the alignment should be in good shape.

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Sam

84 300SD 350K+ miles ( Blue Belle )

What's the measurement across both tires center tread line, middle height off the ground, front and rear of the tires?

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

Also, the outside of that one tire is no bargain either. Since it's only one tire, consider you may have a broken belt in one tire causing premature inside wear.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D