LR extreme tire wear

[troyd]

I have a 93 300 SL that came with factor 16'' wheel. I replaced the factory wheels/tires with a set of used 18 Lorinser Chrome Wheel and a set of new 245/40/ZR18 Tires with 2'' spacers on the rear and 1/2'' spacers on the front. I had to replace the LR tire due to extreme inside wear. I contacted a mercedes dealer to have the alignment checked and they informed me that the factory specs for the alignment won't work with the 18'' wheels and they have no way of knowing what the specs need to be. Standing immediately behind the car and visualizing the rear tires, they appear to "tilt" inwardly. What can I do to ensure that I don't have to continue prematurely replacing tires. I am contemplating replacing the rear spacers with the smaller size and having the alignment done according to specs anyway. Do you think that will help?