First, let's examine how tire tread wear happens, and why you need a self-regenerating tire at all.
Modern radial tires are comprised of a thick rubber outer layer over top of loops or belts of steel and polyester fabric. When these parts are assembled, the rubber part is initially totally bald, until a machine cuts deep patterns into the tire rubber called treads.
Why do tire companies put those grooves into the rubber? Why not just make the tires a bald, smooth surface? If the tires were totally smooth they would have no traction on slippery surfaces. For that reason, tires have tiny grooves and patterns on the outside surface that channel the water away from the contact patch -- where the rubber meets the road surface -- improving the tire's grip.
Different types of tires have different treads based on what kind of vehicle they're used on. Sports cars have very aggressive tire tread patterns because their top priority is handling -- as result of lots of wide grooves, the ride quality on these tires can be harsh. Luxury cars often use less-aggressive patterns because their goal is comfort and low road noise [source: Racerchicks.com].
The problem with tires is that they wear down over time. Subjected to water, heat, acceleration, and braking, the rubber on the tires is gradually shaved off with each use. Most tires have a wear indicator built into them that tell you when it's time for them to be replaced. Tire wear indicators vary from brand to brand, so it might be a good idea to contact your tire's manufacturer to find out exactly what to look for and where.
You risk your safety when you drive on bald tires. When a tire gets worn down, it can't function as well in wet conditions. It's also more susceptible to punctures and blowouts, and your handling and stopping distances are compromised, too. In addition, it's illegal in most states to drive on tires that have worn down to 2/32 of an inch (1.6 millimeters) or less of remaining tread depth [source: Tire Rack]. After a while, your tires need to be replaced. But what if there was a way for tires to last longer by having extra layers of tread that are revealed as the rubber wears down? Michelin found a way to do just that.
In this next section, we'll take a look at Michelin's self-regenerating tire model, XDA5, and examine how it extends tire life up to 30 percent.