A conventional tyre is mounted to a wheel in the usual manner and two urethane components are metered and pumped into the casing via the air valve. The tyre is deliberately punctured at the top, and a hyperdermic or pre-set pressure valve is inserted in the hole. When the polyurethane mixture flows from the hyperdermic all the air has been expelled from the tyre. At this point the hyperdermic is removed, the hole is sealed and pumping continues until the pre-determined equivalent air pressure is reached. The valve is sealed to prevent leakage and the tyre left for approximately 24 hours, by which time the liquid urethane has changed to a resilient solid mass.

A number of suppliers of this process would like to give the impression 'Utopia is here,' as this method combines the attributes of both the pneumatic and the solid. This is far from the case. Granted, the process eliminates normal punctures and the tyre, once filled, can be used with sustained travel speeds up to 50 km/h and intermittently at speeds up to 80 km/h. It could be suitable for on/off highway use, straddle carriers, side-loaders, earthmoving applications, front-end loaders and very big forklift trucks.

1. The maximum load-carrying capacity is no more than the maximum load permitted by, the manufacturer of the pneumatic casing with the equivalent air pressure.
2. The process is no better than casing itself. In other words, a bad cut or slash which penetrates through the casing to the filler, will cause the filler to break down and crumble like granulated sugar and eventually leave a hole which cannot be satisfactorily refilled. The only effective way to rectify this is to replace the damaged tyre with a new tyre, tube and filler.
3. A polyurethane-filled tyre only becomes economically viable when it can be recapped. Strict control must be maintained, the tyre taken out of operation before the tread is worn too far or the tyre will be rejected for recapping. Another problem here is that once the tyre has been filled it cannot be removed from the wheel without either damaging the wheel or tyre. Retreading by the cold method must be done with the tyre on the wheel, resulting in lost production from the machine unless the user has spare wheel and tyre assemblies.
4. The process has been known to cause wheels to break, particularly the two-piece wheels (two halves bolted together). The theory here is that the shock load is transmitted into the bead area, causing flexing at the retaining bolts and eventually the centre dish cracks and breaks.
5. The process is expensive and in many cases if the cost of the tyre, tube and filler is added together and compared with a solid puncture-proof tyre of the same size, the puncture-proof tyre will be cheaper.

Tyre types

• Back to Technical Information.
• Pneumatic tyres.
• Solid rubber puncture proof tyres.
• Press on solid and cushion tyres.
• Urethane press-ons / Bonded tyres.

Other technical information.

• Why Industrial Tyres Fail.
• Rules for longer tyre life.

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