SumoMuffin

I hope this is the proper forum to post this, I figured you all would likely know the most about this.

I obtained a Univega Gran Premio not long ago and have spent considerable time cleaning it, lining the lugs with gold enamel, and touching up the paint. Last night, however, tragedy struck when I realized that there was a fairly large crack in the head tube/down tube lug. I had noticed it before, but just figured it was a imperfection in the paint. So, first question: is it a crack? I know the only definitive way to tell would be to take off the paint, but I'd rather not. Also the bike does seem to have been raced pretty hard back in the day, judging from the components that came with it, dent in the top tube, and the number of knicks in the paint. I'm thinking the crack could have been a result from a frontal crash.

So, question two: is it safe to ride? I would rather not risk it even if the chances of failure are low, but if it's ok it would be great to finish putting the bike together.

Question three: How easy would this be to repair, and is it worth it? I dished out $50 for the bike, and got that worth in components alone (cyclone derailleurs, shimano 600 brakes, stronglight crankset, gran compe stem, etc..)

I was really looking forward to building and riding this bike and have already spent considerable time working on it, but if it's in any way unsafe I don't want to risk it. Any advice or opinions would be greatly appreciated. Sorry for the lengthy post...

unterhausen

sure looks cracked. Do the two closeups show both ends of the crack? Maybe if you take a closeup from either side it would help us figure out why it started. It's a little bit weird for a lug to crack right there unless it started at a stress riser. Don't really see any stress risers.

It's possible it started in the center. Pressed steel lugs have a weld down the center, and there often is a gap at the top of the lug

Andrew R Stewart 

SM- That's a shame. It sure looks like a crack to me but further investigation is warranted. First- can you sight up inside the head tube from the lower end? Is there evidence of the crack coming through there? It's possible the crack (if that is what it is) only goes through the lug (and into a void?) or goes through the DT miter and not the HT. Second- no obvious evidence of the classic head end impact can be seen from the photos. Is there and rippling under the DT or TT? Is the HT end deformed from being circular? Third- the beauty of steel is it's slow failure mode. So if you were to ride the frame you'd keep an eye on the length and spread of the crack. Like every ride. If you see changes then you'd stop and walk (or not ride this bike that day). The repair would be extensive. After documenting the geometry the lug area would be stripped of paint. Further attempts to ascertain the extent of the problem would be done. But assuming the worst the HT, DT and lug would be removed and replaced. I suppose the lug could be ground away from the outside until the underlying tubes and miter face were exposed. Then if the crack didn't enter a tube the lug could be replaced. But this would be quite the undertaking. Lot's of time and still the miter face would have to be melted/broken open. I'd expect a few hundred $ for the more straight forward tubing and lug replacements, before repaint. Perhaps it's time to cut the loss and move on. Andy.

unterhausen

from the way it looks, I'm guessing there is no filler where that is. But it isn't worth fixing

SumoMuffin

With a yearning to know, a good match of touch up paint, and some sand paper I decided to see what was underneath the paint. To my surprise it looks ok! Unless with sanding I smoothed out the crack (is that possible?)

Good point about there being no signs of frontal crash. The head tube is indeed cylindrical and true. The worst ding to the bike is the dent in the top tube, which doesn't seem to be too serious.

There was a pretty large seam of rust under the "crack", though, as can be seen on the edges of the sanded area. I guess it was just an imperfection in the paint. Despite the new knick on the paint, I'm glad to see it wasn't too bad under the paint, it'll go well with the other touched up areas on the frame

So would you all say the frame has a clean bill of health?

Andrew R Stewart 

No. Why did the paint crack where the frame is the stiffest (the thickest amount of metal)? Because some underlying problem is present, IMHO. The first photo (of series #2) might still show a crack. If you sanded across the crack you might see the actual surface issues better. The sanding marks are currently parallel to the possible crack and help hide it. It's good that no deforming damage is present. But I still think that there's a crack in there. Andy.

unterhausen

I wouldn'ta done that.
If you really want to know, you need to polish it to at least 300 grit or so. A closed crack can be very hard to see, especially when you have scratches from 80 grit sandpaper that go in the same direction

SumoMuffin

Ok, understood, that was a dumb move. Later today I'll take it down a little further with perpendicular sanding, then polish it up with a finer grit. I think as of now I will ride the frame, but stop immediately if the crack resurfaces or grows.

SumoMuffin

ok, so I shined it up a bit with 400 grit paper using only strokes perpendicular to the crack. Looking at it under a magnifying lens, the only cracks/scratches that appear to go to an appreciable depth are the couple on the right side. Could imperfections this small really have caused a surface imperfections the size of the one in the first pic?

Not seeing a huge deep crack under the paint has convinced me that the frame is safe. Although I will keep an eye on it. I doubt that cracks this small will cause immediate failure without growing first.

reddog3

I agree with the others, and you'd have a hard time convincing me that it's not a crack. That frame is big with long tubes, and in it's racing career has seen a lot of flexing. And, the dude who rode that frame was big. I'd call the frame used up!

You did a good job of hiding the crack. Put it together and ride it. The crack will resurface if it is indeed a crack. Oh, and do a close inspection of the bottom bracket area as well.