But a lot of consumers don't know it's gone until they're stranded on the side of the road, wondering where their spare tire went.
Over the past few years, several automakers have removed spare tires from the trunk. Some car companies today are making the spare tire an option – costing as much as $350.
In addition to saving fuel, taking out the spare could eliminate the danger of standing on the highway shoulder trying to change a tire while trucks and cars whiz by. Although no one keeps track of how many people die each year changing tires, about 4,000 pedestrians are struck and killed each year, according to the government's Fatality Analysis Reporting System encyclopedia. About 700 of those pedestrians are people working in the roadway.
While some drivers might be shocked to open their trunk and find no spare tire hiding anywhere in the back, the industry says it isn't unsafe to go without. Mandatory tire pressure monitoring systems, which are on all cars since 2006, should alert drivers before their tires deflate. Blowouts are rare, and even if the tire is punctured on the side wall, most drivers have cellphones or access to emergency services through their car.
"Getting rid of something as important as the spare tire wasn't a decision we made lightly," said Terry Connolly, General Motor's director of tire and wheel systems. "The universal implementation of tire pressure monitoring systems over the past five years has significantly reduced the likelihood that a flat tire will leave you stranded by the side of the road."
Chevy, which is owned by GM, eliminated the spare tire on the Chevy Cruze when it debuted last year, and began offering one as a $100 option. In 2011, 85% of customers bought that option, the company says, so they've decided to make it standard equipment again on all Cruze models except the Eco version.
On the Eco model, you can't even get a spare as an option.
"Customers who purchase the Eco are looking for the ultimate in fuel economy and as part of our mass optimization efforts on the Eco model the spare tire is not an option," says Lesley Hettinger, a spokeswoman for GM.
GM says the spare tire saves 26 pounds. That alone doesn't improve fuel economy too much, but the company made 42 other changes in addition to cutting out the spare tire that improve fuel economy by 5%. The Eco version will get 39 mpg on the highway, compared with 37 mpg for the regular models.
The auto industry is under massive pressure to increase fuel economy. One of the ways they do that is by reducing vehicle weight, and when you start looking at heavy things that can be ditched, the spare tire seems like an obvious choice.
There are several models that don't come with standard spare tires, including almost every vehicle that comes with a run-flat tire. To get a spare on a Cadillac CTS, it will cost $350. The Fiat 500 spare tire comes optional for $100. The Ford Focus and Honda Fit don't come with a spare in Canada, but they do in the U.S. Some sports cars don't have them, like some versions of the Ford Mustang, Camaro ZL1, and Audi TT.
The all-wheel drive versions of the Toyota Sienna minivan also don't come with spare tires, but that's because they are equipped with run-flat tires.
Run-flat tires seem like a great compromise between fuel efficiency concerns and consumers desires for lug around a heavy tire "just in case." But they caused problems at first – they wore out quickly, and were expensive to replace. Consumers complained that they got flat tires more often on run flats, and had a hard time finding new run-flat tires at dealers. They can also produce harsher rides, which is especially troublesome since road conditions in snow states have gotten worse the last couple of years.
Newer generations of the tires seem to have fixed some of those problems, says Jennifer Stockburger, program manager of vehicle and child safety at Consumer Reports. Consumer Reports has been tracking run-flat tire wear since 2007, when drivers began complaining about their quality.
Part of the problem was that people didn't know they had them, she says.
"They weren't aware they didn't have a spare tire until something happened," she says. "And then they found out about all these extra problems."
Now, though, run flat tires can last around 40,000 miles if they are taken care of diligently. Consumer Reports has been keeping the tires inflated perfectly and rotating them on schedule, and Stockburger says they haven't had any problems with the tires.
Stockburger says she feels more safe in a car with run flats than one without a spare but with an inflator kit. Inflator kits don't help if the tire is damaged on the sidewall. Run-flat tires give you the ability to get someplace safe, off the side of the road, or even miles down the road to a service station. Not having a spare at all can you leave you stranded if the side-wall of the tire is damaged, or there is no cell signal.
"We don't appreciate that people living in really rural areas sometimes don't have cellphone signals," she says.
AAA expects 1.2 million people will call for help this summer. Many will be flats, but the agency says that many of those could be avoided if people took care of their tires properly.
The group recommends that drivers who buy a car without a spare take into consideration the kinds of roads they travel. "Not having a conventional spare tire would probably not be advisable if an individual travels long distances and on lightly traveled roads," says Mike Calkins, AAA's national manager of approved auto repair. But if virtually all your driving is urban and suburban, you could probably do without.
Membership to AAA costs about $50, depending on where you live. The group frequently responds to calls where drivers have no spare tire, or where the spare is unusable. If the leak is slow, they try to air up the tire and then follow the driver to a nearby repair shop. Some AAA clubs can repair tires roadside, and if that doesn't work, AAA will tow or flatbed a vehicle to a place of repair.
Even though there are ways to work around not having a spare, some customers are uncomfortable with the idea. Tim Huckaby, a reader in Fort Worth, Texas, says he simply won't buy a car without a spare. He's had to change tires by the side of the road several times, and can't see going without one.
"It has come in handy several times ... I want and need the spare," he says.