Spare tire on car

Spare Tires in New Cars: What You Need To Know
June 7, 2016 – 09:51 am
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They hide in the dark corners of our trunks. We don't give them a second thought until we need them. And when we do, they come out to save the day. A spare tire is an unsung hero, able to get us back on the road in a matter of minutes. But what if you reached into the trunk and found no spare tire in your new car? What if, in its place, you found a shoebox-size device with a power plug?

Decades ago, nearly every car came with a full-size spare tire. But fuel economy requirements, trunk space considerations and safety concerns have prompted automakers to shift toward smaller temporary spares. In some vehicles, there's no spare at all.

Although carmakers are working to come up with new spare tire options for their cars, the reality is that most people just reach for the phone when they have a flat.

"Our research says that only about half the people who have spare tires actually use them when they have a flat, " says Dave Cowger, engineering group manager for General Motors tire engineering. "Because of the convenience of roadside assistance, many of them make that call even if they have a spare."

Whether you ultimately choose to change your flat tire or not, it's good to familiarize yourself with the different types of spares as part of new-car shopping research. At the very least, it's worth asking about the spare system when you're finalizing a purchase. That way, you won't be caught off-guard when you go looking for a spare that might not be there.

Full-Size Spares
A full-size spare is the same size as the other tires on the vehicle. Full-size spares come in matching and non-matching varieties. A matching spare is identical to the other wheels and tires on the vehicle. A non-matching full-size spare typically has a lighter-weight construction and a shallower tread depth that reduces vehicle weight to improve fuel economy and make the spare easier to install, according to Tire

There has been a 49 percent decrease (accounting for about 64 models) in vehicles that come equipped with full-size spares since 2007. Except for trucks or larger SUVs, full-size spares have disappeared from the majority of passenger cars.

While they are the biggest and heaviest of the spares, full-size tires offer virtually no performance loss. If you have a matching spare, you have the flexibility to get the tire fixed at your convenience, rather than immediately, which you would have to do if you had a temporary spare. Full-size spares must be incorporated into the vehicle's rotation pattern to ensure a long tread life and balanced handling characteristics.

Temporary Spares
Automakers have shifted to temporary spare tires or "donuts" because they offer the best balance between size and usability. Temporary spares are the most common choice for automakers and can be found on 52 percent of 2014 models. That's a 7 percent increase from 2007, according to specifications tracked by the Edmunds data team. Temporary spares are smaller than the vehicle's other tires, take up less trunk space and are light enough for most people to handle when they're changing a flat.

"Temporary spares are developed to approximate your vehicle's optimum handling, " says Kurt Berger, manager of consumer products engineering for Bridgestone Tire, which provides tires for many automakers. "The carmaker and tire maker go out of their way to develop that temporary spare to minimize the handling difference."

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