These tyres are very expensive and were developed for I.C.engined or electric-powered trucks and trailers operating under conditions where a very high tyre load-carrying capacity and longwear characteristics are prime requirements. Because of the high load carrying capacity much smaller wheels can be utilised enabling truck designers to reduce the overall dimensions of the machines.
Generally, it is possible to replace a rubber tyre with a urethane one, but if the machine was designed around a urethane tyre it is not possible to replace it with a similar-sized rubber tyre as this will grossly overload the rubber. Although these tyres have a high resistance to oil and petrol contamination, they are not generally recommended for use where solvents, acids and alkalies present a regular problem. Variations in the hardness of the material from 830 shore to 950 shore are available. This variation gives totally different physical properties as can be seen from the graphs on adhesion and ground, contact.
Urethane has good wear characteristics, high load carrying capacity, a high resistance to oils and grease and is generally better than rubber in sub-zero temperatures. However, its tractive ability is poor and its melting point is very much lower than rubber. It also tends to be brittle and normal expansion joints in the floor can cause it to crack and chip.
Generally this material is utilised on pallet rollers, reach trucks and small hand-operated trailers. Certain reach trucks use urethane tyres which have a bevelled base band. The two halves of the wheel bolt together. Users have experienced problems when refitting tyres after the original has worn away. Usually the problem is that the wheel moves inside the new tyre. Usually the cause is because the two halves of the wheel were just pushed in and bolted together. The correct method is to freeze the wheel before fitting the new tyre. As the process is very expensive, some industrial tyre distributors offer a re-bonding service either to the existing wheel or rim, or in certain cases, service exchange facilities. This considerably reduces the cost.
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