I'm amazed there's so few retro bikers without tweed.*
Not the poncey posh tweed of Sovile Row, but real manly rough Harris Tweed, unlined naturally - and that's just the undies.
It's actually the original outdoor gear - good for our climate. Highly breathable, handles most rain short of a downpour (when you put on your waterproofs) and doesn't get smelly. Working man's gear.
I've got a nice bolt of Harris Tweed in the attic - made by my uncle 30 years ago - trouble is it has a bit of purple in it, but maybe I should get it turned into a jacket and breeches. I've been looking for a copy of the original CTC patterns from the 1890s because the designs were for practical use on the bike as opposed to fashion. I think they used Norfolk Tweed for that.