I think that some makes DO actually ruggedize their larger size designs for anticipated heavier and stronger riders. Others, obviously, don't.

Clydes (and ESPECIALLY us "UberClydes") should carefully inspect models before purchase. Things to carefully look at (and ask about) are the seat rails, the seat post, the pedal axles, the wheels, the stem, and the handlebars. With "racing" frames that use carbon parts, be especially vigilant about the frame, too.

When I say "ask about," I don't mean asking the sales kid either! Most sales kids are part-time, untrained, and are in the shop because of their enthusiasm for bikes and their willingness to work for starvation wages. The sales kids (mostly) aren't competent to answer your questions on weight-limits of individual components. Find the web-site of the bike manufacturer. Usually, the site won't answer your questions either, but there will be a "contact us" e-mail link. ASK THE MANUFACTURER what the limits are for their components! I've had 100% response from every site I've asked questions on (except for Mavic, and that's another story).

Never assume that parts are designed for you. Only by asking can you ensure your safety. As one who has been in an accident caused by parts failure, I can promise you that safety is worth asking about.