The evolution of motorcycle tyres has shown a steady improvement in grip, acceleration, braking and turning, along with a corresponding improvement in comfort, safety, durability and reliability. This has led to a steady increase in tyre width, and created a mindset amongst riders that the size of the tyre directly correlates to performance; the bigger the tyre is, the better it must be. While the various advances in materials and construction have resulted in multiple benefits, it is worth noting that factors such as tyre width, diameter, cross-section curvature, geometry of the motorcycle the tyres are intended for are all factors which will ultimately affect its performance.
Invented by John Boyd Dunlop in 1888, pneumatic tyres, which make use of gas and pressurised air were commonly used on bicycles and some early motorcycle prototypes by 1895. Used on the first production motorcycle, the 1894–1897 Hildebrand & Wolfmüller, pneumatic tyres have been on nearly all production and special motorcycles ever since. Tyre sizes back then were usually 22 to 28 inches in diameter and 1.5 to 2 inches wide.
Made of all metal, or a combination of wood and metal, the early models of the pneumatic tyres were spoked and used inner tubes to hold air. Due to poor, uneven roads, flats were a constant problem. For easy repair, butt-ended or open ended inner tubes were used, and some brands made rear wheels easier to detach. Spoked wheels with tubes remained the standard until the 1970s, till solid wheels, usually alloy, began to appear and eventually dominate the market, making lighter tubeless tyres practical.
As the motorcycle industry progressed, larger tyre sizes went hand in hand with larger engine displacements. By 1909 –1914, 2.25 inch section, 26 inch diameter tyres were used on 250 to 350 cc motorcycles, and 2.375 to 2.5 in section tyres appeared on motorcycles with displacements over 350 cc. Indian tyres reached 3.0 inch × 28 inch, giving even greater rider comfort but with a taller seat height.
From 1915 to 1929, tyre quality continued to increase, and beaded edge tyres began to be replaced by wired-on beads. Steel loops were also embedded in the tyre’s edge to prevent it from expanding under pressure. With a greater range of tyre sizes appearing on the market, the typical tyre grip also further increased by 40%, resulting in better cornering, shorter stopping distance and overall improved safety. A variety of rubber compounds, natural and synthetic rubber and tread patterns further expanded the options. Tyres specialised for wet roads, smooth dry roads, racing, off-road use, and sidecars also appeared on the market.
It was during the early 70s where the increasing widths of tyres led to major changes in road racing cornering techniques. The cross section became more oval, and the greater width of the tyre resulted in the contact patch being further off centre. This increased the steering effort or turn radius, at a given lean angle and speed, than it would have been with a rounder profile. Techniques such as hanging off or knee dragging, in which the rider moves his body far off centre for the purpose of changing the centre of gravity of both the rider and bike in order to turn at a given radius and speed. Racer John Surtees had been quoted saying, “The idea is to keep the machine as upright as possible for maximum traction.”
The first radial tyres for motorbikes were the 1983 Pirelli MP7 radials, first introduced on the European version of the 1984 Honda VF1000R, a limited edition motorcycle that showcased a number of new technologies including carbon fibre reinforced bodywork and air-adjustable anti-dive front forks. Radial tyres allow the tyres to run cooler yet maintain great flexibility. This allows for significant increases in both grip and tread life under a broader range of conditions than bias-ply tyres.
In part 2 of this series, we will look at the different types of motorcycle tyres in greater detail.