We've discussed this before. Natural rubber is white. "Early" cars had white tyres..............
Wiki...........
The use of whitewall rubber for tire has been traced to a small tire company in Chicago called Vogue Tyre and Rubber Co that made them for their horse and chauffeur drawn carriages in 1914.[1]
Early automobile tires were made of pure natural rubber with various chemicals mixed into the tread compounds to make them wear better.[2] The best of these was zinc oxide, a pure white substance that increased traction and also made the entire tire white.[2] However, the white rubber did not offer sufficient endurance, so carbon black was added to the rubber to greatly increase tread life.[3] Using carbon black only in the tread produced tires with inner and outer sidewalls of white rubber. Later, entirely black tires became available, the still extant white sidewalls being covered with a somewhat thin, black colored layer of rubber. Should a black sidewall tire have been severely scuffed against a curb, the underlying white rubber would be revealed; it is in a similar manner that raised white letter (RWL) tires are made.
