You’re driving down the highway, and boom, your right rear tire has blown out. You find yourself battling to maintain control of the car as you head to the shoulder. Once parked, you open the trunk, expecting to find a spare tire, but instead you see a “donut” or perhaps an air compressor with a can of sealant.
So a donut vs a spare: which is better? And does it even really matter?
A Donut vs a Spare
Until recently, new cars came equipped with a full-size matching spare tire, one that could easily be rotated in with the other tires. In some cases vehicles are outfitted with a full-size non-matching spare, one that doesn’t have the exact perimeters of the standard four tires and, therefore, cannot be used in your tire rotation.
In the interest of saving room and weight, many manufacturers have since opted to place what is known as a donut, a compact temporary tire, in the compartment where the spare is usually located.
A donut is designed to get the job done, but there are some important differences.
First, the tire pressure is much higher, typically as high as 60 PSI. Second, a donut can usually only be driven at speeds of up to only 50 mph. This means if your breakdown is on the interstate, you’ll be forced to stay in the far right lane and hope that the traffic is light. Go faster than the spare’s speed limitation and you risk another blow out. Third, handling and other features are altered. Indeed, if your car has anti-lock brakes and traction control, a compact temporary tire will greatly impact performance.
So clearly, a donut is a interim measure. Certainly, it can get you back on the road again, but you’ll need to have the spare replaced as soon as you can, as donut tires are designed for a quick fix only.
Sealant and Inflator Kits
In a further effort to save weight and manage room, some car manufacturers have done away with the spare tire completely. They go beyond the donut vs a spare debate by equipping vehicles with sealant and an inflator kit.
Typically, kits like this are found in cars without run-flat tires. Run-flats are designed to allow you to keep driving for a limited distance when suffering a minor puncture. In effect, you’ll have enough air left in the damaged tire to get to a service station. The downside is that these tires won’t do you any good if the sidewall is sliced or if there is some other type of major problem.
For cars without run flat tires, manufacturers may place an air compressor and sealant in the storage compartment. The first item inflates a tire back to its normal pressure and the second seals the puncture. Together, the two are designed to handle minor punctures and get you back on the road. The downside is that if you have a blow out, you’ll have no choice but to call for roadside assistance to replace the destroyed tire.
Notably, the donut vs a spare or compressor and sealant debate also reveals that manufacturers are looking for additional ways to save money. Thus, if you are shopping for a new car, it’s crucial to know what you’re getting. Inspect the spare tire compartment and if you want a full-size tire, then negotiate with the dealer to guarantee you get one.
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Photo courtesy of Mathew Keegan
Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.