A flat tire is always a nuisance. At best, they are inconvenient. At worst, they are costly and potentially dangerous. However, there is an assortment of aftermarket emergency flat tire repair products that hold the promise of getting you back on the road quickly, without having to mount a spare tire or call a tow truck.
These types of products have been around for years. They work by pumping a sealant into a flat tire, plugging small punctures from the inside. Sealant kit popularity has been accelerating as they become common-place on new cars, where they are replacing the traditional spare tire for sake of weight and fuel consumption savings.
To assess how the latest products work, our tire team took a break from their schedule of testing almost 500 tires this year to evaluate two types of repair kits:
Pressurized-can sealers ($7.50 to $10), such as the ubiquitous Fix-A-Flat, are one-time-use products that have a dispensing tube that screws to a tire’s air-inflation valve. These sealers can both patch a hole and inflate the tire.
Tire-sealant kits ($20 to $80) combine a portable 12-volt air compressor and a replaceable container of sealant. More and more new cars supply this kind of kit in lieu of a spare tire.
Despite their roles, these products are not spare tires in a can. They should only be used for tires that are technically repairable, by sealing a small hole only in the tread, and with the understanding that the fix is strictly temporary. No attempt should be made to repair a hole larger than 6 mm in diameter or a cut or hole in a sidewall. With that kind of damage, your only option is replacing the tire.
If you use a tire sealant, you should get the tire professionally repaired or replaced as quickly as possible—typically within 100 miles or as directed by the product.
Sealants coat the inside of the tire and wheel with a messy residue, which a tire shop has to clean out, possibly causing extra expense. They can potentially gum up the tire-pressure monitor sensor (TPMS), if so equipped, risking erroneous readings. However, in our tests, we had no sensor become inoperable. Typically the sensors needed to cleaned after using a sealant. Some products specifically claim they are TPMS safe.