The 2020 Ford Explorer will offer tires that fix themselves. Drivers may not even know they ran over a nail, but here’s what they should know:

The tires allow them keep traveling after a puncture, in some cases continuing for days without a repair. They use different technology than run-flat tires, which have been criticized for rough rides.

Most drivers won’t even know they had a puncture until they notice a nail stuck in the tire or tire-pressure warnings alert them to a gradual loss of air pressure days after the puncture, according to Michelin engineers.

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The concept of self-sealing tires has been around for years, but recent improvements — and automakers’ eagerness to save weight by eliminating conventional spares — means we’re going to see more of them.

“Self-sealing tires are designed to handle the most common tire puncture — a small object penetrating the tire in the tread area,” said Woody Rogers, director of tire information for online retailer the Tire Rack.

Most drivers never know'

Michelin makes the Explorer’s self-sealing tires. It also supplies them to the Chevrolet Bolt. Most major tiremakers have tires with the technology, and the number of choices is only likely to grow.

The inside of the tires is coated with viscous goop that flows into punctures to seal them.

“When the sealant works as designed, most drivers never know it’s working. There is no pressure loss, and odds are the driver doesn’t see the object in the tire or it’s fallen out,” Rogers said.

Creating the rubbery sealant was tricky, Michelin engineers said. It must flow into punctures, but it can’t pool at the bottom of the tire when it’s parked. The material also must form an airtight seal, and flow at temperatures from scorching desert blacktop to a frigid winter night.

Unlike run-flat tires, which have stiff sides that allow them to keep rolling after the air leaks out, self-sealing tires can keep going for days after a nail or similar object punctures them.

Run-flats, which first became common on sports cars that didn’t have room to carry a spare, wear out quickly after losing pressure. They may provide a range of just 50 miles or so before the tire must be replaced.

Michelin’s tires can theoretically keep going for days, though they will eventually need to be repaired or replaced, depending on how severely the puncture damaged the tire. Neither technology is much help when the tires’ sidewall is shredded, as can happen with potholes.

Michelin calls the technology Selfseal. Continental, which supplies self-sealing tires to brands ranging from Volkswagen to Bentley, calls its version ContiSeal.

Convenience at a cost

Michelin’s tires can seal punctures up to a quarter-inch. Continental makes a similar claim: one-fifth of an inch.

The tires will be standard on the 2020 Explorer Limited hybrid and Platinum models and optional on the Explorer Limited.

Other tire brands that offer self-sealing tires include Hankook and Pirelli.