The spare wheel, which is no longer available as standard in more and more new cars, suggests that it can be dispensed with, since punctures have become a rarity.

The ADAC automobile club estimates their statistical risk at around 100,000 kilometers or eight years.

Run-flat tires with emergency running properties and the tire pressure monitoring system that has been installed in all new cars since 2014 further reduce risk awareness.

Until one day it happened: flat or damaged tires alone caused almost 250,000 calls for the ADAC road patrol last year, seven percent of all assistance.

That's why researchers in the tire industry have been pondering the vision of the indestructible tire for a number of years.

Reminiscences of the early days of automobiles are by no means taboo.

After all, puncture-proof solid rubber tires were state of the art before the French Michelin brothers first fitted the air-filled tires to Peugeot and Panhard vehicles in 1895, which had been invented by the Irish veterinarian John Boyd Dunlop (1840-1921) seven years earlier.

The distrust of the newfangled invention grew with the skyrocketing number of flat tires.

Quite a few car manufacturers were therefore still delivering their vehicles with the tried-and-tested solid rubber tires decades later.

The last known passenger car equipped with it was a Trojan from 1929 by the British manufacturer of the same name from Croydon.

(By the way, he continued to build the German Heinkel cabin scooter as the Trojan 200 after its end of production from 1961 to 1965.) In Germany, the solid rubber tires on trucks survived even longer, until the road traffic registration regulations on November 13, 1937 for all vehicles with more than 25 km/h h Maximum speed prohibited.

Since then it has only existed on forklifts, handcarts or handcarts.

Flexible and highly resistant spoke

Michelin has been researching the absolute puncture resistance of modern tires for around ten years and has now registered 15 patents for airless concept tires.

In 2017, the Vision Concept was presented, an extremely light wheel and tire unit made of aluminium, composite materials and rubber tread.

Two years later, the French presented the Uptis tire prototype for passenger cars, developed jointly with General Motors, and have since been testing it in long-term tests on the Chevrolet Bolt electric car, identical in construction to the Opel Ampera-e.

The first driving tests on public roads are planned for this year in Michigan.

In the Michelin Uptis, the rim is connected to the tread, which has a profile similar to that of conventional pneumatic tires, via flexible and highly resistant spokes made of polyester resin and glass fibre.

The outer material is insensitive to impact and puncture injuries, explains Head of Development Eric Vinesse: "With the Uptis, drivers can be sure in the future that they will never again have a flat tire due to pressure loss." The market launch of series tires is planned for 2024.

According to Vinesse, the environmental balance of the NPT tires (Non Pneumatic Tires) is exemplary: “Currently, around 200 million tires around the world have to be disposed of every year because of consequential damage caused by pressure loss, although they are far from having reached the end of their service life.

NPT tires are therefore a benefit for the environment.” Of course, it remains to be clarified whether this also applies to the manufacture and disposal of the innards used.

Conflicting goals between wet grip and rolling resistance

Michael Rachita from Goodyear also mentions avoiding waste and conserving resources as important plus points in addition to reliability.

The American manufacturer is currently testing airless tires on autonomous vehicles and delivery robots.

The results in terms of wear, braking performance and vibration damping are positive, and approval for normal road vehicles in the United States is expected in a few years.

By 2030, the aim is to bring the first maintenance-free tires made from sustainable materials onto the market.

Christian Koch, head of the Dekra tire laboratory in Munich, answers the question about the prospects for NPT tires: "The technologies that have become known so far definitely offer potential.

Because of the necessary inflation pressure, it is difficult for conventional tires to resolve certain conflicting goals.

For example, due to the internal pressure, the tire contour is curved in the longitudinal and lateral direction, which affects durability, grip and driving characteristics.

Without the internal pressure factor, the parameters can be set more independently of one another.

The tire thus offers developers more opportunities to optimize it for the respective application," says Koch, adding: "Certain conflicting goals, for example between optimum wet grip and minimum rolling resistance, will remain,

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