I'm 275 and I have a schwinn cutter and now a new scrambler. With my schwinn I just have 36's and really everything I've ridden from friends and what not hasn't buckled and crumpled. It's a bike steel or aluminium find something your size and a decent spoke count and start riding. As far as ratio I live in a kind of hilly area depending on where you ride and my preference is something higher I would rather crank out then spin out. I'm riding 42,17 right now hitch I hate so I'm going to 48,15 at least.