Kurt,
I never really considered this question. I have always assumed that latex inner tubes predate butyl inner tubes because latex rubber products in general predate the invention of butyl rubber. I think (I'm sure someone will correct me) that butyl rubber was originally made by adding carbon black to natural latex. It gave the rubber better durability. Then again, maybe I'm confused. It may be the vulcanizing process that I'm thinking of. Vulcanizing also improves durability and I think it was vulcanizing that allowed for the development of rubber-treaded tires. I also recall that during some war or another (hows that for vague?) the development of totally syntheic (petrochemical based?) butyl was a major priority for whichever side lost access to SE Asian rubber supplies. Since the French were in that area specifically for the rubber, I assume the synthetic rubber was invented by the Germans. Just a guess.
Anyway, I have little doubt that both latex and butyl inner tubes both in widespread use in tubular tires decades before 1976.
Tom Dalton Bethlehem, PA
__________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com