A spare tire is a helpful safety net, but most are not meant to replace your flat tire indefinitely.
Not all spare tires are created equal, so check your vehicle owner’s manual to get a better understanding of what kind of substitute you have. Temporary spare tires usually don’t have nearly the lifespan of a regular tire. In comparison to a normal car tire they can have just one layer of polyester in the sidewall and two belts of steel with a layer of polyester in the tread, meaning they can’t take nearly as much road abuse as a normal tire.
These smaller spare tires are usually called space-savers, or donuts. They’re popular choices since they’re lightweight and don’t take up a lot of room in the cargo space of a vehicle. Since they’re lighter, they’re also easier for the average person to lift and install.
However, since they’re smaller and more compact, they’re missing out on two key aspects of a regular tire: durability and stability. Most of these spare tires have a limited top speed of 55 mph. You can expect to get about 50 miles on a spare tire like this, and some are rated up to 70 miles. That should be enough for you to find a mechanic who can patch up your flat, or a tire shop where you can replace the punctured tire.
FULL SIZE SPARE TIRES
Some automakers also provide a full-size spare tire, although these are heavier and take up more space, they’re robust and durable. These should be able to last you much longer than the donut, or space-saver types of tires. However, they may use a different tread make-up or a different kind of rubber compound than the rest of your tires. This can affect overall handling and safety on the road. While they are more durable, these kind of spare tires are designed to help you get to your destination before you have to deal with your flat tire.
DON’T HAVE A SPARE?
If you don’t have a spare, your car may be equipped with run-flat tires. BMW and MINI tend to equip vehicles with these kinds of tires right from the factory. These kinds of tires are tougher than most kinds of tires, and can withstand a puncture and keep on going. However, they’re not designed to go on forever.
Most run-flat tires recommend that you replace them shortly after noticing a puncture. They’re usually only rated to run up to 50 miles after being punctured before needing a replacement.
Some shops can patch up a run-flat tire, but OEMs don’t always recommend that path. Compared to regular tires, replacement run-flats are quite expensive. Other automakers have resorted to just providing a flat tire repair kit in the car, in order to save weight and costs. Instructions for this job can be found in the owners manual.
The bottom line is that if you have a flat tire, you should get it replaced. Spares are temporary replacements, and while full-size spares may be the same size as your regular tire, they may not be the same kind of tire, which can result in some problems.
Remember, your car’s tires are the only thing connecting you and your family to the road, so don’t gamble on safety.