1992 Toyota Corolla • 180,000 miles

When I m driving slowly, like 30km/h, my car shakes, its not the string ok, but when I drive like 40km/hr it will be ok and when I got at the speed of 100km/hr the string shakes a bit, but my tire is new, with 195/50 r 15, I checked it three mechanics but they said the tire is bad but which is not, I already checked and put balance on each wheel, what shall I do about it, thank you so much !
November 13, 2012.

Defective new tires is not unheard of but not as common as in the past. Balance is not the issue. Have them balanced on a "road-force" balancer. That will show up variations in how the sidewalls flex in different areas, and it will show up a bent wheel. If they all pass, have the wheels measured for "lateral runout" on the car. If a wheel is found to be wobbling sideways as it rotates, look for debris sticking between the brake rotor and wheel or that fell between the brake rotor and hub.

Nov 13, 2012.