I hate to bump such an old thread, but my father has this exact same problem on a CPO 2002 s500. In fact it was so bad, that you couldn't tell the inside rib was completely bald until a tire ruptured on him during a long trip. After the tire burst, I refused to let my father put his life in danger driving the car until I could get to the bottom of this. It's been sitting for over a year and I just recently had time to work on this.

Crown Mercedes in Birmingham, AL told me this type of wear is normal, which I don't believe. All the other 4 ribs on the tire have wear, but aren't bald. I believe this is an alignment issue that the original dealership in Cary, NC never actually did. Several other things wrong with the car like the traction control, headlight aim, etc as we drove back to AL after purchasing it in NC. I think this car was never properly CPO'd.

So is this type of tire wear normal on the w220 s500? Or do you agree with my suspicions on it not being properly CPO'd?

 

The usual pattern for old W126 S-classes (1980's, through 1991), assuming they are aligned well, and using the recommended tire pressures, is for the fronts to wear both inner and outer shoulders, whereas the rears are inflated more, and tend to wear either flat, or potentially a bit more in the center-tread, so that rotating front to back will tend to equalize the wear a bit.

But even with regular rotations, the net effect is that the rapid shoulder-wear on the fronts tends to dominate. I keep my fronts pumped up with a bit more pressure than recommended, to try and even the wear out a bit.

The old W126's go through tires relatively quickly, in any case, due to the wheels and tires being fairly small for the size/weight of the car.

In terms of left/right variation - I would think that even with misalignment you would expect the effects of toe-in or toe-out to show up on both sides. That said, on my own car, it seems like if anything the driver side wears a bit faster than the passenger side. Perhaps this is due to the fact that right turns tend to be sharper than left turns, since you aren't able to angle across the oncoming lane(s)? Just a speculation on my part....

 

This is just a thought, it happened to me on the right front tyre, check if your rim is buckled. You may need to get the rim rolled. This is what is going to solve my issue.