Mercedes Benz 300sd Car pulls to one direction.

Steering problem
Mercedes Benz 300sd 4 cyl Two Wheel Drive Automatic 71000 miles

Hello there.I just have my car aligned (but not get a balance or tire rotation) and the it keeps pulling to the right.

There is no obvious diagnostic I can make since the car slightly shifts to the right when driving fast, slow or breaking. The only hint I can give is that I feel that the problem is in the front, since it goes strait when going up in a ramp. The car is rear wheel drive.

I have checked the tire pressure and they are fine. The car has performance tires. What could be the problem? Can a balance and tire rotation cure the problem?

Thanks !