Say you just bought a new car, and the right front tire goes flat as you're driving down the freeway. Don't be surprised if there's no spare when you look in the trunk.
This year, more than 14 percent of new models on sale in the United States came with liquid tire sealant and a portable electric air pump instead of a spare, a trend that is growing as automakers try to shed pounds and boost gas mileage.
Although the sealant doesn't fix every flat, General Motors, Hyundai and other automakers that use the kits say they have many advantages — mainly the weight savings. The kits are about 20 pounds lighter than a temporary spare and the jack and other tools needed to put on the tire. Also, the inflator kits don't take up as much room in the trunk, leaving more space for luggage or other cargo.
- Automakers say tire sealant is reliable, but they recommend checking a few miles after fixing a flat to see if the tire needs a little more air.
- GM also recommends that people drive no more than 100 miles before getting a sealed tire repaired. GM says drivers can travel at normal highway speeds after sealing a leak.
- While the sealant works well in most cases, you could be stuck on the shoulder if the hole that caused the flat is larger than a quarter of an inch, or if the puncture is on the side of the tire. In those cases, it's best to have your car towed to a repair shop.
GM, which has made inflators and sealant standard on all but five of its 22 U.S. car and crossover models, says the kits can fix 85 percent of tire punctures. They're easy to use, even for someone who might be afraid of changing a tire, says Dave Cowger, GM's tire engineering group manager. The company's market research shows that half of consumers would rather call for roadside assistance than use a spare, he says.
Cowger adds that the kits are also safer because tires can be quickly refilled, getting the driver off the roadside and back in traffic faster than putting on a spare. Hyundai says the inflator kits help avoid another problem: getting dirty while changing a tire. All you do is attach some tubes and fill the tire with sealant and air.
Still, for the 85 percent of flats that the sealant can fix, there are 15 percent that it can't. That's why Honda uses spares on all its 2011 models, spokesman Chuck Schifsky says.
"An actual spare tire is the best backup system should a customer have a flat tire," he says. "This is especially true in cases where the tire is damaged beyond what the tire sealant and pump systems can repair."
The move away from spares is likely to grow as automakers face pressure to meet stricter government fuel-economy regulations. By 2025, the U.S. car and truck fleet will have to average 54.5 mpg under the standards, which are being phased in gradually. That's about double what cars and trucks now get.
Automakers "need to find any way they can to reduce the weight of the vehicle, which will in turn make it more fuel efficient," says Ronald Montoya, consumer advice associate with the Edmunds.com automotive website.
It's something automakers say needs to be done, even if people are hesitant to put their spares aside.
"All manufacturers are looking at this," says Alan Batey, U.S. vice president of Chevrolet sales and service. "This is one opportunity to get weight out of vehicles and make them more fuel-efficient. ... It will take some time for people to understand this technology."