Cracked seat lug
- Thread starter Peterc123
- Start date
bulgie
Dirt Disciple
I'm a retired framebuilder and a bit of a bike snob, so my opinion may be a bit harsh, but that looks like careless and/or unskilled brazing to me. Yes I know how to tell paint issues from braze issues, paint doesn't fool me.
I don't know the builder, is he considered one of the good ones? I don't want to judge someone by the worst bit of brazing he ever did, but if that's his normal, then I'd say return it and wait for something better.
With all due respect to @vcballbat, I think welding it is a very bad idea. If you get good weld penetration (as you should), you will be vaporizing the brazing filler underneath, and nearby braze on the outside too, where the seatstay attaches to the lug. Brazing filler mixing with a weld makes the weld all frothy and brittle.
Maybe you're a better welder than I am, but I have never heard of a successful weld repair over a brazed joint. And I know plenty of people who've tried it. Brass (or silver) anywhere near the weld is a deal-breaker.
Fillet-brazing (as we say in the US — maybe you lot call it "bronze welding"?) over the whole lug is a valid repair method. If smoothed out well, it can be — and look — not only "as good as new" but in fact better, won't ever crack there again.
Rebrazing the seatstay cap where it looks like the braze is cracking is difficult though, hard to get braze to penetrate inside the crack due to the corrosion inside, that you can't clean up without removing the cap entirely.
Removing the cap, cleaning and making a new cap is prossible, but more work than this frame is worth.
Replacing a seat lug is beyond difficult, I'd put it more in the "impossible" category. Sure, nothing is impossible, but I'd rather make a new frame than replace that lug. Only worth it for an extremely rare Holy Grail frame, like maybe if Reg Harris won a World Championships on it.
I don't know the builder, is he considered one of the good ones? I don't want to judge someone by the worst bit of brazing he ever did, but if that's his normal, then I'd say return it and wait for something better.
With all due respect to @vcballbat, I think welding it is a very bad idea. If you get good weld penetration (as you should), you will be vaporizing the brazing filler underneath, and nearby braze on the outside too, where the seatstay attaches to the lug. Brazing filler mixing with a weld makes the weld all frothy and brittle.
Maybe you're a better welder than I am, but I have never heard of a successful weld repair over a brazed joint. And I know plenty of people who've tried it. Brass (or silver) anywhere near the weld is a deal-breaker.
Fillet-brazing (as we say in the US — maybe you lot call it "bronze welding"?) over the whole lug is a valid repair method. If smoothed out well, it can be — and look — not only "as good as new" but in fact better, won't ever crack there again.
Rebrazing the seatstay cap where it looks like the braze is cracking is difficult though, hard to get braze to penetrate inside the crack due to the corrosion inside, that you can't clean up without removing the cap entirely.
Removing the cap, cleaning and making a new cap is prossible, but more work than this frame is worth.
Replacing a seat lug is beyond difficult, I'd put it more in the "impossible" category. Sure, nothing is impossible, but I'd rather make a new frame than replace that lug. Only worth it for an extremely rare Holy Grail frame, like maybe if Reg Harris won a World Championships on it.
vcballbat
Senior Retro Guru
Try not to overthink it, a small blob of weld on the small crack on the thick steel lug with localised heat shouldn't be a problem and would certainly get you out of the shit, that's the beauty of steel...it can be fused back together
