Tire Technology: Running out of Air

The electric drive is challenging automotive certainties. Obviously, electric cars currently still run on round tires filled with air. But it’s becoming apparent that electric cars will need new footwear. And that they might even manage entirely without air. We asked DEKRA tire experts about the newest tire trends.

You’d think that the tire industry should be able to take a relaxed approach to the transition to electromobility. After all, it has recently demonstrated remarkable innovative strength. Manufacturers’ portfolios include tires that automatically seal minor damage to the tread with the help of an integrated sealant. There are tires with enormously resistant structures in the tread only made possible through 3D printers. In addition, there are intelligent technologies that not only monitor air pressure and wear, but also provide information about road conditions, thus promoting tires themselves to players of networked mobility. So it seems reasonable to assume that tires which fit cars with a conventional drive system are also the right choice for an electric vehicle. But a near miss is still a miss. In truth, the tire industry is currently under tremendous pressure.

The Electric Drive Is a Challenge for Tire Developers

“Electromobility is changing the demands on tires,” explains Christian Koch, tire expert and head of the analysis department at DEKRA’s Munich branch. According to the report, electric vehicles weigh more than internal combustion vehicles, their center of gravity is lower, and the wheel loads are distributed differently. “You need more air volume to carry the vehicle weight. The tires therefore become either larger or wider,” the DEKRA expert knows. However, this development triggers a number of conflicting goals. If tire diameter increases, this can have negative consequences for roll comfort and roll noise. An important parameter is the driving dynamic of the electric drive. If you constantly push your electric car to its full potential with heavy acceleration and frequent braking, you’ll pay a price in the form of high tire wear. “Experts assume that tires on electric cars can have a wear rate of up to 40 percent higher than that of a comparable combustion engine with a corresponding driving style,” explains Christian Koch.

Roll Resistance Moves to the Top of Developers’ Specifications

Vehicle manufacturers are also calling on the tire industry. Across all vehicle classes, they expect perfectly tuned tires on which electric cars can even add kilometers to their range. As a result, roll resistance is once again at the top of developers’ list of specifications. The right lever already seems to have been found. “The industry trend is leaning toward sustainability and lightweight construction. Many manufacturers already rely on high-tech recycling processes that make it possible to use renewable materials as fillers for tires,” reports Christian Koch.

The “Conti GreenConcept” tire study just presented at IAA Mobility, for example, contains a high proportion of renewable and recycled materials. These include rubber from dandelions, silicate from the ashes of rice husks, as well as vegetable oils and resins. In addition to recycled steel and carbon-particulate matter, they use polyester from recycled PET bottles in a tire’s casing. Continental says they have significantly reduced weight and roll resistance of the concept tire – roll resistance is around 25 percent below that of a tire with roll resistance class A in the EU tire label.

Will Michelin Sideline the Pneumatic Tire Before Long?

Tire manufacturer Michelin is breaking new ground with “Uptis” – the abbreviation stands for Unique Puncture-proof Tire System. The concept tire doesn’t use air as a carrier medium. The French have been working on the airless tire for about four years and presented the latest version of this technology in the middle of the year. The Michelin Uptis foregoes the previous separation of wheel and tire. The concept, which has already proven itself on test drives in North America, relies instead on an extremely lightweight wheel-tire combination in which an aluminum rim is inseparably connected to slats made of rubber, polyester resin, and carbon fiber, as well as to the tread, via flexible and extremely resistant plastic spokes. The tire system promises high performance and durability – flat tires, as well as curb damage to flanks and casings thus become a thing of the past. DEKRA expert Christian Koch sees tangible advantages in the concept: “The Uptis basically excludes air as an uncertainty factor. This eliminates a major disadvantage for roll resistance and abrasion because, in practice, the inflation pressure often isn’t optimal due to lack of monitoring.” His conclusion is therefore clear: “Hats off for making it all work.”