True tire color on WWI aircraft?

[Fritz Kempf]

Here is the smooth gray tire sold by Coker.



Ed

[cfgray]

I've made an admittedly incomplete study of the color of pre-WW1 aeroplanes tires, and some of what I've found may be applicable to the newer (WW1-era) aerial machines' tires.
GoodYear aeroplane tire samples (dating from the pre-1920 period) have a soft light buff/grey color, when gently scraped to reveal an underlying surface. This is due not only to the fact that they were made of natural latex, but also due to the fact that they contained additives. Natural Latex is not the ideal "rubber" substance many might think it is. If unvulcanized it becomes brittle and cracks. Even after vulcanization, which involved the reaction of sulphur and latex (along with oils) and which gave the rubber more body, more strength and made it less sticky, natural latex would dry out, harden and crack after long exposure to ultraviolet light (read: sunlight).
Talc was also added to latex as well, to reduce stickiness and to limit the effect of ultraviolet light, which yielded the light color seen on early tires.
Near the end of or during WW1, carbon-black powder was added to further reduce the effect of ultraviolet light, and it also improved the wear and traction of tires and increased the rolling resistance.
Brick Red rubber color tires (seen in old automobile racing tires and old innertubes) involved an additive (which I do not recall and do not have access to my notes since I'm on vacation - it may well have been iron oxide powder) which yielded the least rolling resistance (at the cost of less traction) - making it and ideal for early race cars. They were not used on aeroplanes, however, because they did not wear well and were heavier, requiring the addition of more layers of fabric to provide the strength afforded by the addition of carbon-black.
I have a piece of a red tire from Barney Oldfield's Mercer racer which he crashed in 1913 or 1914, and it is as hard as a rock, and flakes and cracks very easily.
So, to shorten this, the light colored tires, as used on early aeroplanes, were a light buff-grey. The black tires, seen on many early aeroplanes in museums, are generally from later production (and hence post-date the aeroplanes), after the addition of carbon-black became universal.
The darker tires (such as seen on the photo of the Albatros, posted by Petern) could well have been the light buff-grey tires darkened through use (staining) and exposure.
Coker white tires, by the way, are far too raw white (as are whitewalls of tires) to give an accurate impression of the actual color of old aeroplane tires. Coker grey tires are too grey, not buff enough.
Hope some of this is useful,
Best,
cfgray

- when I say "light buff/grey" I mean a light predominently grey color which is also light yellow/brown with pinkish tones, at least that is how I would describe the color I saw within the outer layer of the ca. 1911 "Good Year Aeroplane" tire