Okay, first off, that title is not meant as a dare!
At one time, every vehicle had a full-size spare tire that was just like the other four. Even then, though, that spare could end up deflated over time, since air molecules can migrate through the slightly-porous rubber of the tire and through the valve stem. And even if the tire was fully inflated, the rubber could dry-rot over time and degrade to a point where the tire couldn’t hold together. So, long story short, driving at highway speed on a spare tire was a dicey proposition even 30 or 40 years ago.
Then in the 90s, most manufacturers went over to the “donut” or “space saver” spare. The donut spare was designed to cut weight and take up less space in a vehicle — although if space is a problem, you still need to figure out how to haul the tire that failed. Donut spare tires are smaller in size than the OEM tires on your vehicle, and generally have a speed rating of about 50 mph.
That smaller size will also throw off your vehicle’s antilock brakes and traction control systems, and can conceivably affect speedometer readings and transmission shift points if the tire is left on for too long. You’ll also notice that your vehicle’s handling, braking performance and road manners will be negatively affected, so the bottom line here is that you should keep your speed down to 50 or less on a spare tire and should get it replaced with an OEM-size tire as soon as humanly possible.
Many new vehicles are no longer even offered with a spare tire. Some are equipped with run-flat tires that allow you to keep going even after a complete loss of air pressure, others have an aerosol sealant that can re-inflate a tire and seal a puncture, while others leave you to rely on the manufacturer’s roadside assistance in an emergency.
So, to get to the answer to the title of this blog: if you find yourself driving on a spare, whether it’s a space saver or full-size, you need to consider it an emergency option. Keep your speed below 50 miles an hour and try to drive 50 miles or less until you can get the tire repaired or replaced.