Originally Posted by polymorphself

You’re gonna wanna look for ones with 531 or Vitus tubing (or equivalent) as mentioned above. Those will already be light frames and will certainly come with alloy components. Short of that, steel wheels and components will hold you back more than the frame (unless it’s a schwinn, you can never overcome that weight), and any old mixte frame and fork will be light enough If you want to build it up yourself with alloy wheels, cranks, stem etc. as I did here...