Why where motorcycle tires made before 1915 white? And why did tire engineers add carbon black, making the tires black after that? Check out this insightful history article brought to you by this motorcycle trader.
The first production inflatable tires were made by Scottish inventor John Boyd Dunlop in 1888. He originally made them for his sons tricycle out of canvas bonded with liquid rubber. Realizing how efficient they were on the tricycle he later fitted them to a bicycle and the rest of course is history.
Some other tire manufacturers you may have heard of started their bicycle and/or automotive tire business soon thereafter, such as: Goodyear (1898), Michelin (1889), Pirelli (1890), Metzeler (1892), Continental (1898) and Firestone (1900). Since the original motorcycles made were essentially modified bicycles, all production motorcycles, including the first Hildebrand & Wolfmüller, had inflatable tires.
The very first motorcycle tires (1894-1909) were between 22-28 inches in diameter and 1 1/2 – 2 inches wide. The wheels were spoked made either entirely out of metal or metal and wood, and the tires used inner tubes to hold air.
As the engine displacement and weight of the motorcycles grew, so did the tires width. By 1914 Indian motorcycles used 3 inch tires on 28 inch rims. These tires were constructed with a cross ply, or a bias tire construction, with body ply cords that extend diagonally from bead to bead at an angle between 30-55 degrees, with successive plies laid at opposing angles forming a crisscross pattern to which the
tread is applied.
Tread patterns had been invented for bicycles already during the late 1890s, with either protuberances of raised rubber buttons or indentations of depressed transverse slots. The manufacturers experimented with more complex patterns of indentations and protuberances in the years to come, and still do to this very day.
Before 1915 motorcycle tires were highly sensitive to ultraviolet light, or sunlight. The tire manufacturers discovered that by adding carbon black, which is a material produced by the incomplete combustion of heavy petroleum products, the tires had greater resistance to sunlight and also got better thermal stability.
This is why tires from before 1915 were white in color, which is the color of natural rubber. Tires of the time were also very flexible due to the way the tire attached to the wheel by a clincher interlock. This led Michelin engineers to try and find a solution, which they did using wired-on beads, which used steel loops embedded in the tires edge to prevent it from expanding under pressure.
The solution was implemented by all manufacturers in the coming years and by 1930 all motorcycle tires and rims where designed in this way. Another limitation of the tires of the time was the use of only natural rubber, but in 1909 German Organic chemist Frits Hofmann discovered Synthetic rubber. Natural rubber has great mechanical performance at constant temperatures but is thermally unstable, or in other words, as the temperature in the tire increases, its performance decreases fast.
So adding synthetic rubber made the tires a lot more thermally stable. The cross ply, or bias ply construction of the tires were severely flawed by the fact that as the sidewalls flexed, they generated loads of heat.