Framebuilders - 531 top tube crack!!! Any vintage experts out there?

This link was originally posted in Collectible/Vintage, but someone suggested that the experience on these matters would be here.

http://www.bikeforums.net/showthread.php?611324-Vintage-531-Frame-small-crack-split-in-top-tube&p=10194898

Basically I have an early 70's bike with butted Reynolds 531 whose top tube has a very tiny lengthwise hairline crack on the underside of the tube... just off of the center of the tube. It is barely and inch long and was imperceptible until I began a detailed polishing.

There is no rust anywhere and the metal has not (so far as I can tell) separated at the split area. There is a barely noticeable eruption that I can hardly see but I can feel if I run my fingers across the split.

The bike is too nice to consider repairs that will destroy the aesthetics. So I am left with a choice of hanging it up or riding it only occasionally.

What are your thoughts as professionals and artisans? Is a small split on the top tube of a 40 year old bike a serious problem or is it just something to be aware of? I am not a hard rider, and I don't intend on riding this but for the nicest of days.

All input will be greatly appreciated.:D

Pictures, gotta have pictures.

I responded in the other thread. I assume it's a scratch, especially if there is no rust.

There are usually vent holes into the head tube and possibly the seat tube from the top tube. You could pressurize the top tube and see if it leaks. Or look at it under magnification.

I've handled hundreds of 531 tubes, and never seen one with a significant problem. Like I said in the other thread, it's always possible that it was a defective tube because there was some hand manipulation. I've just never seen a bad one.

Here are some photos. Remember... it is not just a paint scratch, if you run your fingers over it you can feel a slight eruption in the metal.

http://i805.photobucket.com/albums/yy338/ivandarken/CIMG4983.jpg

http://i805.photobucket.com/albums/yy338/ivandarken/CIMG4984.jpg

I responded in the other thread. I assume it's a scratch, especially if there is no rust.

There are usually vent holes into the head tube and possibly the seat tube from the top tube. You could pressurize the top tube and see if it leaks. Or look at it under magnification.

I've handled hundreds of 531 tubes, and never seen one with a significant problem. Like I said in the other thread, it's always possible that it was a defective tube because there was some hand manipulation. I've just never seen a bad one.

You are on target. Most likely a die mark or fixture mark on the tube made during tubing manufacture or frame construction before painting. Also the mark is very straight and parallel to the tube axis. i do not believe a top tube crack would propagate in that direction based on top tube loading.

I certainly see why you think it's cracked. I'm still open to the idea that something else is going on. This is what some people call a "crack indication."

if it is cracked, it does seem like a defect in the tube's manufacture. There isn't a lot of stress driving a crack in that direction, so my interpretation would be that there just isn't a lot of material along that line. So a replacement makes the most sense if that is economic. Bicycle frames don't just crack out in the middle of a tube, they crack at the ends or at braze on locations. Something has to be drastically wrong with a tube for a crack to occur in that location.

What brand is it?

I wouldn't ride it, but then again I tend to ride my bikes pretty hard. If you aren't going to be riding down any mountains, I'd probably just ride it and monitor it. I would be a lot more concerned if there was something near a lug.

No rust suggests that it might not be the tube. If you REALLY want to find out, sand off the paint in the area of the crack to visualize the metal directly. If it is a crack, drill out the ends and fill the whole thing with silver solder.

It will be much more appropriate to hang it on a wall than to go full on into surgery. After all, her road racing days are far behind her.

I just want to make sure that once I have it completely cleaned up, that my occasional leisurely rides on it won't end up in catastrophy.

I find it strange that such highly regarded tubing, high end for the era, would fall victim to manufacturing anomalies. Ours is not a perfect world.

It is a steel frame. Run it by a machine shop and have them magnaflux it. That will tell if it is cracked. It is not an invasive test (shouldn't require sanding the paint).

http://en.wikipedia.org/wiki/Magnaflux