Wheels of Fortune

The tyre of the future needs no air and will envelop all obstacles in its path. Tom Stewart checks out the spin

I saw a communication from an old school pal recently. It turns out he's been employed by the same tyre maker for many years, and his career summary read: "Still trying to make 'em rounder and blacker for humanity."

I saw a communication from an old school pal recently. It turns out he's been employed by the same tyre maker for many years, and his career summary read: "Still trying to make 'em rounder and blacker for humanity."

While new tread designs, profiles and marketing campaigns are about as common as punctures, aside from a flurry of invention around the turn of the last century, major leaps in tyre technology don't happen often.

One year after Charles Goodyear invented vulcanised rubber in 1844, Robert Thompson invented the pneumatic tyre, albeit a leather one. In 1888 John Dunlop made the first rubber pneumatic tyre for his son's tricycle, and then André Michelin fitted something similar to a motorcar in 1895.

Goodyear patented the tubeless tyre in 1903, and the following year saw rim design first allow for tyre/tube removal and puncture repair, as well as Continental producing the first pneumatic tyre with tread. In 1910 BF Goodrich reduced wear by adding carbon to the rubber mix. Synthetic rubbers were introduced in the mid-1930s, followed by Michelin's invention of the radial tyre in 1948. Goodyear's first commercial exploitation of its earlier patent came in 1954 when tubeless tyres were fitted to a Packard.

The early 1970s saw more activity with Dunlop eschewing car inner-tubes, radials finally finding market acceptance, the successful introduction of treadless slicks in motor racing and the launch of Dunlop's Denovo, the first so-called run-flat.

While Bridgestone, Continental, Dunlop, Goodyear and Pirelli have all pursued the reinforced sidewall approach to run-flat design, Michelin has achieved extended run-flat capability, energy saving and more with its complex PAX system. Available now for certain Audis, Renaults and Rolls-Royces, this has a bespoke wheel with a supple, non-pneumatic inner ring that supports the outer pneumatic tyre in the event of pressure loss.

Continental has it's "Conti Support Ring", currently approved for the Maybach limo. This is a metal ring on a flexible mount fitted within a conventional tyre on a conventional rim. In the event of pressure loss, the tyre is supported by the ring and, like the PAX, the vehicle maintains composure at speeds of up to 50mph for a distance of approximately 125 miles.

Arguably the most significant development in car tyres for many decades is Michelin's Tweel - an integrated tyre and wheel that doesn't need air. It's already in production for the iBot stair-climbing wheelchair.

The Tweel is a one-piece wheel with a treaded-rubber contact band bonded to flexible spokes. These are fused to a shock-absorbing inner hub, which in turn bolts to the vehicle. Michelin predicts that the Tweel will deliver pneumatic-like performance and can "envelop" road hazards.

With a conventional tyre, any increase in lateral stiffness - either through increased air pressure and/or stiffer sidewalls - will result in a harsher ride, but there's no such compromise with the Tweel. Michelin claims to have increased lateral stiffness by a factor of five, improving handling and steering.

There are some negatives. At present it is no lighter than the pneumatic radial it's due to replace, and, despite the theory, it's flexibility and ride comfort are apparently still short of what customers want. But Michelin expects to have these issues solved prior to it coming to market in eight to 10 years' time.

Less dramatic in appearance but also under development is Michelin's Airless tyre. It has an internal radial structure made of closely spaced metallic arches and composite materials with a bonded rubber tread band. Easily re-treaded, the Airless is intended to last as long as the vehicle it's fitted to.

Also keeping Michelin research scientists busy is the Active Wheel project. This is a conventional tyre (at this stage) with active electric suspension, a small disc brake and an electric motor inside the rim to assist traction and braking. Active Wheel-equipped cars might be made without gearboxes, transmissions and differentials, and could potentially switch from front- to rear- to four-wheel-drive as required. Among the intended benefits of the system are reduced weight, improved economy and more compact vehicle packaging.

The next time a tyre man tells me he's busy making them rounder and blacker, I'll suspect he's being economic with the truth.