I have a 1972 TR6R with a Easy Rider sidecar. My question is what size or make front tire should I be running and what tire pressure should I run front and rear? If and when my wife ever rides with me is not a problem as she only weighs something like 90lbs. My Easy Rider sidecar looks something like a Spirit Eagle.
I am assuming the Easy Rider is a pretty light weight fiberglass sidecar. If so, I would run a 4x19 tire and start off with around 32 lbs in the front and 36 lbs in the rear. I would also put a 75 lb weight in the sidecar under the seat (a barbell plate works nicely). I would also put a hydraulic steering damper on it, if it doesn't have one (the hydraulic strut for an old VW hatch works nicely and is cheap). You will want pretty wide handlebars for leverage. I use K&N Superbike bars. They have a low rise but are pretty wide. This is all based on the Velorex sidecar I had on my Norton Atlas.
Avon do a sidecar tire in 3.50 X 19. However the Avon Speedmaster Mk II has a 4.00 X 19 variant which gives you a bit more width for extra life and is a pretty square profile. I have fitted the latter to my URAL outfit (sorry about the swearing) and am well pleased with it. Much better thasn the Russian crap rubber on originally. HTH