When filled with mud or snow, airless tyres become like Fred Flinstone’s chariot
MICHELIN’S airless tyre, the Tweel concept, lobbed 11 years ago and was a modern interpretation of the old buggy wheel. Except this time, the ‘spokes’ were a lattice-like interwoven structure that absorbed road shocks like a pneumatic tyre. Michelin has gone quiet on the Tweel, but Bridgestone showed something similar with its airless tyre, the Air Free Concept, at the 2013 Tokyo Motor Show.
The Air Free Concept tyre has a spoke structure made from reusable thermoplastic resin that stretches along the inner sides of the tyres to support the vehicle’s weight. Along with the rubber tread, the materials used in the tyres are all recyclable.
Both the Michelin and Bridgestone tyres have a problem with the lattice-like absorbent part of the tyre: when filled with mud (especially when dried) or snow, they become like Fred Flintstone’s chariot wheels – there is no give in the tyre. The other problem is that, in Bridgestone’s case, the tyres only support a vehicle weighing 410kg and have a maximum 60km/h speed. The airless tyre has a way to go yet before it’s a production reality.
The closest thing to a puncture-free (air-filled) tyre is Continental’s Contiseal tyre, which has a sticky, viscous layer from shoulder to shoulder along the inner carcass. It’s not designed or intended to act as a permanent puncture repair; it’s more like an automatic plug repair kit.
If an object up to 5mm in diameter penetrates the tread, the Contiseal layer envelopes the puncturing object and gives a near instantaneous seal. If the puncturing object becomes dislodged from the tyre, the material is designed to seal most holes up to 5mm in diameter. Continental claims there is no tyre performance detriment, but it’s currently not offered in its 4WD tyre range.
Michelin’s Tweel concept tyre has a ways to go yet!