The tan is the natural color of rubber-impregnated cotton casing; the black tread is carbon-black reinforced rubber laid over it. Gumwalls are what tires looked like before fashion covered the casing.
Monsoon Cycles, Colorado Springs · Updated August 16, 2026
Early tires were all casing: cotton cords dipped in natural rubber, honey-tan by chemistry, with tread rubber added only where the road touches. Carbon black, which strengthens tread compounds, turned racing tires black; wrapping the sidewall in black too was a style decision that took over mid-century. The tan revival is partly nostalgia and partly honesty, since a supple high-thread casing is something to show off.
Our renderer takes them seriously: the game and Frame Lab draw the tread cap wrapping the casing shoulders at the true proportions of a classic open tubular, not a painted stripe.