I remember reading about these. Looks like the idea never went anywhere...
TwinTire(tm) tyres.
This is an idea from the USA based on the twin tyres used in Western Australia on their police vehicles. It's long been the practice for closed-wheel racing cars, such as Nascar vehicles, to use two inner tubes inside each tyre, allowing for different pressures inside the same tyre. They also allow for proper run-flat puncture capability. Well, it seems that TwinTires have put the same principle into effect for those of us with road-going cars. Their system uses specially designed wheel rims to go with their own unique type of tyres. Each wheel rim is actually molded as two half-width rims joined together. The TwinTires tyres then fit these double rims. Effectively, you're getting two independent tyres per wheel, each with their own inner tube or tubeless pressure. The most obvious advantage of this system is that it is an almost failsafe puncture proof tyre. As most punctures are caused by single objects entering the tyre at a single point, with this system, only one tyre will deflate, leaving the other untouched so that your vehicle is still controllable. TwinTires themselves actually claim a reduction in braking distance too. Typically from 150ft down to 120ft when braking from a fixed 70mph. The other advantage is that the system is effectively an evolution of the Aquatread type single tyres that can be bought over the counter. In the dry, you have more or less the same contact area as a normal tyre. In the wet, most of the water is channeled into the gap between the two tyres leaving (supposedly) a much more efficient wet contact patch. Time will tell whether this system is just a passing fad or if it will take off as a viable alternative to the standard wheel/tyre combos that we all use. Typical tyre sizes are 125/85-R16 and 125/90-R16 (Yokohama and Avon).
For an independent opinion on TwinTyre systems from someone who's been using them since the year dot, have a read of his e-mail to me which has a lot of information in it.
http://www.chris-longhurst.com/carbi...yre_bible.html