I want an 18" rear tire for 850G

[Guest]

Does anyone know if there is an 18" wheel that will work on my 1980 850G? If I can go up to an 18 it would help out with tire selection as I am building a sidecar rig...just wondering if it is even possible.

[Grimly]

As far as I know, no cast shafties were made in 18", but there's a wire wheel option - the rear from a Madura could be re-rimmed. Some of the later model shafty cruisers with wire wheels will likely fit too, and though they're a far wider rim, I suspect the hubs will fit. The advantage of a Madura conversion is they were narrow and of that generation.
Or, you could try what I'm doing, eventually - get a 15" rear from a Cavalcade and go Darkside. The biggest hassle is the narrowness within the GS850 swingarm, which effectively rules out anything wider than 145 section (and that, only if you do some jiggering around with brake arm clearance).
I'm going Darkside just for the hell of it, but if I were running a chair, it would be a priority.