Check the load rating on the side of the tire. If your towing it should be a C or a D. These tires have thicker side walls and allow higher tire pressures which help to reduce sway in the tow vehicle.

Example, I have Michelin LTX tires. You can buy these tires in four different load ranges.
The Tire Rack is a good place to research tires and purchase.
Tire Rack


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