A total of 28% of 2017 model-year vehicles lack a spare tire as standard equipment, according to recent AAA research.

The growing trend to ditch the spare tire is largely driven by an effort to reduce weight and improve fuel economy. But lack of a spare tire can create unnecessary hassle and expense in the event of a flat tire, AAA warned.

“Having a flat tire can be a nuisance for drivers, but not having a spare could put them in an even more aggravating situation,” said John Nielsen, AAA’s managing director of automotive engineering and repair. “This can turn the relatively routine process of changing a tire at the roadside into an inconvenient and costly situation that requires a tow to a repair facility.”

While new vehicles are equipped with tire pressure monitoring systems that alert drivers to low tire pressure, AAA’s roadside assistance data shows that tire-related problems continue to be one of the top reasons why members call for assistance. Even if drivers do have a spare tire, they are often reaching for their cell phones to call for roadside assistance rather than changing the tire themselves. According to a previous AAA survey, nearly 20% (39 million) of U.S. drivers don’t know how to change a flat tire.

As a replacement for a spare tire, some automakers are including tire-inflator kits that can temporarily repair small punctures in flat tires. However, a 2015 AAA study found that tire-inflator kits have limited functionality and cannot provide even a temporary fix for many tire-related problems, including sidewall damage or blowouts.

Not only are tire-inflator kits not a good substitute for a spare tire, they can cost up to 10 times more than a tire repair and have a shelf life of only four to eight years, according to AAA.

“With low-profile tires and the elimination of a spare tire, many newer vehicles are especially vulnerable to roadside tire trouble,” Nielsen said. “AAA urges drivers to make it a priority to check their vehicle’s equipment and know what to do if faced with a flat tire.”

To learn more about spare tire availability among 2017 models, click here.