I’ve been asked why we use radial tyres instead of bias tyres. Without going into a deep technical discussion the most appropriate analogy is to use early diesel engines compared to the modern common rail diesel.In past times diesels were slow and dirty and whilst reliable they were rarely used in performance vehicles. With the advent of common rail injection systems diesel engine vehicles have become high performance machines. Bias tyres were the original design of tyre developers such as Messrs Dunlop and Goodyear. Layers of cotton or canvas were impregnated with rubber to form the structure to support the tread package that engages with the pavement. The Michelin brothers developed the modern radial tyre using steel cords laid in a radial pattern to form the structure of the tyre to support the tread.
The advantages of radials are manifold for instance the handling performance is superior with increased grip for improved steering and braking. For OTR tyres the major advantage is that the tyre structure runs a lot cooler so a harder tread (read more durable) compound can be applied. This in turn permits extended tyre life which when combined with superior handling provides end users economic pluses.
From a manufacturing position radials are a lot easier to produce than bias tyres. Radials are lighter in overall mass thus require less energy input but also importantly fewer resources (eg less rubber). The actual structure of a radial is lighter than the same size bias tyre as there are fewer components within the structure. When a green tyre is cured the physical depth of rubber is the critical factor for curing time. A radial having fewer components and layers when compared to a bias tyre has a reduced curing time. Thus more tyres can be produced from the building machines and curing moulds generating increased efficiencies and throughput for the tyre manufacturer.
From a tyre servicing perspective, the radial is a lot easier to handle. The bias design and construction requires a broad bead face (to encompass the multiple bead bundles) whereas a radial has a single bead. Radial tyres will literally fall off a wheel/rim base when being demounted whereas bias tyres more often than not require a press or specialist hydraulic equipment to demount them.
When we compare bias and radial OTR tyres of the same size and load (mass) rating the radial has a substantially higher TKPH value (work capacity) so it will carry more load at a higher average speed, exactly what modern mining operations require. Like any high performance machine there is a price to pay.
Regardless of the design philosophy of a tyre they both serve the same function, ie to retain the inflation medium (air) that supports the loads applied (mass, speed, cornering etc). As we all know and appreciate a flat tyre does not work at all well so having the appropriate inflation level is critical to not only safety but also the economics of your operation. A radial tyre is more sensitive to variations in tyre inflation pressures but with modern electronics tyre pressures can be monitored in real time to ensure the highest productivity is achievable.
Maintain your tyres on a frequent and regular basis, ideally use a real time TPMS. Engage knowledgeable service providers who will enhance your operations making it safer and more profitable. Tyres are the foundation of the modern motor vehicle (regardless of size), if the tyres are “not right” then the vehicle (your car or a giant mining truck) will not respond as the driver reasonably expects it will. Look after your tyres so they will look after you!
With special thanks to Adam Gosling, TyreSafe Australia, for his work on this article