How do you convert a womens bike frame into a mans bike frame?

Answer 1

I'm not certain what it is that you want to do. If you're talking about cutting the top tube out of a "boy's" frame to turn it into a "girl's" frame I'd advise against it. Frames need a certain lengthwise stiffness, and it's unlikely that a frame designed to be a closed triangle would be strong enough if you cut part of it out. Besides, the whole concept of boy frames and girl frames is patently silly. It originated back in the day when women weren't allowed to show their legs in public and rode in long skirts and dresses. Functionally it's a poorer design, and unless the rider has problems getting hers/his legs over the top tube there's no sensible reason in getting a girls/womens frame.

If you're talking about moving parts from a "boys" bike to a "girls" bike, well, that's mostly doable. Mostly becacuse there are a few different standards, and it's unlikely that all the parts will fit. Kids bikes aren't particularly expensive, so it'd probably be more rational to get another bike from Craigslist, eBay or similar.

Answer 2

I want to do this with my bike too. I think you need to cut the top tube off, then find a tube of metal the same width as the old one then cut it to the right size, then weld it in the position of a mans frame. You would also have to paint it afterwards.

But bicycle tubing is fairly thin-walled, and quite difficult to weld. A better option is brazing. Better yet, get a used bike with a man's frame instead.