Expert advice please ... !

My car is a 1987 W124 300E, right hand drive.

Both of my rear tires have been wearing out excessively fast.

First, I have changed to a new set of 4 Yokohama AVS Sports 205/55/16. Both of the rear tires were completely worn out after 5,000 km ONLY. The front pairs were OK. Pressure of all 4 tires were about 250 psi.

Then I changed the rear pair (only the rear) to Falken tires; at the same time, my mechanic had changed the two lower arm links of both back wheels. Pressure of all 4 tires had been reduced to 210 psi.

By now I have run about 10,000 km but the rear tires seem to be about 85% worn out already. The front pair of Yokohama are still OK, about only 50% worn out.

Notice that always the left back tire worn out more than the right back tire.

HELP ... what could have gone wrong? This is frustrating.