The most important and most dangerous compromise concerns the handling and safety of your car. Being so narrow doesn’t help too much with the steering and the braking. This affects the car’s handling and could lead to potentially unsafe situations. Especially when braking or accelerating hard, you will have unequal forces that could make the car pull to the side with the spare wheel, so it’s easy to end up in a ditch or the incoming traffic.
This is why it’s recommended to drive slowly and gently when on a donut tire, and by slowly, we mean no more than 50 mph (80 kph). While you can drive on the highway, it is safer to stay off of them as you should only go as fast as 50 mph. Also, keep in mind that electronic stability control and traction control systems will not work properly with a compact spare.
So, it is understood that you should drive as little as possible while you have this kind of tire on your car, but everybody has different understandings of what that means. Maybe you’re in the middle of nowhere, and the next car repair shop is 100 miles (160 km) away. But this is one of those extreme situations that can’t be taken as a reference. As a rule of thumb, you should not drive more than 70 miles (115 km) with a donut tire, although some experts do recommend not exceeding 50 miles (80 km).
This is because a donut tire is not made like regular tires. They are less durable and cannot take the driving abuse as a normal tire would. The rubber they’re made of is of inferior quality and is a lot thinner than in a regular tire. This also means that you will have to throw them away when they get punctured or damaged, as they cannot be repaired. They are called temporary for a reason.
Being so frail doesn’t mean they will have to be replaced more often, though, as most drivers would not even use them for the life of their cars. But rubber will decay with time, and even when not used, the spare tire will have to be replaced eventually. This stands true no matter whether you have a regular spare tire or a donut tire. Except that, with a regular spare, you can (and should) include it in your tire rotation routine, whereas with a donut tire, you may not. Experts recommend replacing the donut tire after ten years. After that, even though the tire may look fine, its structural integrity might be compromised.
In the end, you should know that both regular spare tires and donut spare tires have pros and cons and the use of one or the other depends on your car and driving habits. Usually, heavier cars or those that go off-road will have a regular spare tire, while smaller passenger cars will do with donut tires. Of course, a full spare is preferable to a donut type, but in most cases, that would not be practical since it claims more space from the car’s trunk. Also, when your car has a flat tire, you will be thankful if it has a donut tire as opposed to a TireFit repair kit.