Manufacturers suggest that donut tires, or compact spares, be driven no faster than 50 miles per hour. In addition, they recommend these tires only be used for short trips and a total distance of 50 miles.
A spare should be replaced with a full-size tire as soon as possible because it affects the safety of the vehicle. Their smaller size and narrower width diminish the vehicles' braking systems, traction control and ability to corner. And, unlike a full-size tire, a compact spare has fewer plies, or layers of polyester and steel, to make it strong. Thus, it is not as resistant to wear or punctures and should not be patched if it blows out.