the BT45 are available in 3.25/19 front and 4.00/18 rear, at least here in europe they are. that's what bridgestone recommends for the 550.
Thats weird, I've looked for a while and can't find anything.
I don't want to stray too far from stock, but I guess 100f/110r would be ok. Issue mainly is for my front; the fender is very close to the sidewalls on my current tire. I could modify the fender if it's an issue, though.
I'm not part of the camp that wants a wider tire for looks. It's just not necessary for our bikes with the little horsepower they make. Plus, tires can be heavy, haha.
Thanks for the thoughts, I'll order something this week. Also against my better judgement I might be getting the Motogadget chronoclassic 10k rpm tavh soon...after that, I think I'll have a complete bike!