I never had a problem running the Avon Storm ST 120/70-18 up front on the stock wheel. Fitment seemed to be fine as far as my knowledge could tell. Didn't seem to be "wrapped" to tight
With the RC rear wheel from UFO, (I don't know how wide it is) I ran a 180/55-18 with no issues or washer swap using stock swing arm..
I'm partial to Avons, have had very good luck with them. Stick well, handle well, and wear well.
The front is one of the few I've run that doesn't start doing weird shit due to cupping before I get the chance to use it all up. These run true right down to almost bald.
With after market wheels and notched swing arm.
Avon Storm ST 120/70-18 its a sport touring tire.
Avon Cobra 200/55-18 cruiser tire, if I had it to do over would have gone with a 17" rear. There are no sport tires in 18" over about 160mm wide last time I looked.
The RC wheels are as heavy as stock if not more. Shoulda bought Cazz's
With the 200 in back I have to deflate the tire and loosen the rear pumpkin bolts and its still a fight to get it in and out.