Bicycle Mechanics - Steel Frame Question

My friend wants me to take his three old bikes and cobble together one bike that works. I need some advice as how/where to inspect an old steel frame for rust, previous accidents, etc. Anything that would help me choose the best frame to build up. All three are his old bikes so I assume the frame size is OK on each.

Thanks in advance.

Look for chipped paint around the connecting points of the frame. This is an indication of damage. Especially look for paint that has a bubble or fractured glass look.

You can also check to make sure the frame is straight. This mostly relates to the rear stays being straight. Sorry, the method to check is more involved than I want to write about here, but there are many bike books that describe how to check. See your library or do an internet search.

Frontal impact will casue a ripple or bend just behind the head tube.
You can check the general alignment with some string threaded from the rear dropout around the headtube and back. The seat-tube should be centered between the two bits of string.
For a guide to quality, look at the rear dropouts. better frames uses moulded rather than stamped metal dropouts.
Rust attacks worst at the bottom, where the chainstay joins the bottom bracket.

MichaelW,
In the case of a frontal impact, how hard would it be to repair the down tube? I passed up a Miyata 210 a couple weeks ago for that reason.

Do do it right the tube has to be replaced. Usually not cost effective unless the frame is pretty special.A frame isn't necessarily ruined or structurally compromised if the downtube gink is relatively minor.The fork might be trashd though.

Do do it right the tube has to be replaced. Usually not cost effective unless the frame is pretty special.A frame isn't necessarily ruined or structurally compromised if the downtube gink is relatively minor.The fork might be trashd though.

Is there anyway to tell for sure if a frame is still structurally sound? I have an old frame that has some paint cracking behind the head tube lugs and a small kink in the top tube. The fork is in good shape. Is there anyway for a frame to get that kind of cracking without messing up the fork?

-Jon

It's possible to have a heavy-duty fork that'll hold up in a wreck. Also depends upon the orientation of the impact forces as well. If you catch some air and aimed the front-end downwards, so that you hit with the fork-blades vertical, the fork wouldn't bend much, but the frame can end up bent.

if the paint is cracking, pick some of it away with the tip of a knife or razor and see if the metal is cracked underneath. Cracks without deformation/elongation of the metal is typically fatigue and it'll probably start extending the crack adn cracking elsewhere. However forced bends aren't usually too much of a problem if they're minor and the geometry's not compromized.