A car spare tire is exclusively meant for use in emergency situations, or as a short term change for a flat or damaged tire. It is not intended for everyday or extended use, and tire manufacturers have specific specification for their usage.
Compact spare tires, equally known as donuts, are thin tires made with a space-saving design. Because there is such a small amount of inflated rubber to check the impact of the vehicle over bumps and there is so little tread, they are produced for extremely limited use. Basically, if the spare tire has been mounted, it is meant to be changed as soon as possible.
Compact spare tires:
- Are intended for use at speeds no higher than 50 mph.
- Are to be used for a cumulative distance of no more than 50 miles.
- Are not for use with all-wheel drive cars, nor for vehicles with four-wheel drive engaged.
Full-sized spare tires:
- Should not be used for a period longer than necessary due to mismatching speed ratings and load ranges.
- Should be changed when the tread is worn or the tire is ten years of age or older according to the sidewall date.
The full-sized spare tires used to be much more commonplace than they are now because of their versatility. In many situations, the spare tire could be mounted on the car and simply rotated into use. Slowly they gave way for compact spare tire usage, which took up much less cargo space. If your car has a full-sized spare, it is likely designated as a spare tire and not a passenger-use tire. It should not put it to use as a long-term replacement for a flat or damaged tire on your car.
If you have experienced a flat tire and have used your spare tire, inspect the specifications on the sidewall to know if it needs to be changed or can be stored again for future use. Check the manufacture date on the sidewall to know if the tire is over 10 years old. If it is, have it changed, irrespective of condition, for your own safety.