Access to rubber from the tropics also seems relevant.

Rubber is also not needed. Leather and springs will do the job.

https://onlinebicyclemuseum.co.uk/wp-content/uploads/2014/05...

Ball bearings were invented after the bicycle. Belive it or not, but people on a budget would still get bikes without bearings up until the interwar period.

Every pre-modern wagon had a big old bucket of grease hung at the side of it. It was needed to keep the axle continuously lubricated. (Sayings about wheels and grease are preserved to this day.)

Theoretically, a two-wheeled transportation contraption could have been made, but having to carry the grease with you would make it pointless.

Same sayings about grease and bikes existed as well. Its not theoretically, bikes with plain bearings were made and ridden.