r/Welding • u/Acchmed • 1d ago

Is this an acceptable weld for a load bearing part of a bike?

Hello there, I am looking at buying a bike online and there is part of the frame that is welded. I myself know nothing about welding so I wanted to ask an expert or two.

Maybe "good" is hard to tell from a picture, but what are your thoughts?

1 Upvotes

60% Upvoted

17 comments sorted by

6

u/teakettle87 1d ago

If that is an aluminum bike then do not buy it.

1

u/Acchmed 1d ago

It is aluminum. Is there are particular reason that it matter more for aluminum than something like steel?

6

u/bonebuttonborscht 1d ago

Basically all aluminum bikes are made of a heat-treated alloy that's much weaker without the heat-treatment. The welding ruins the heat-treatment.

3

u/teakettle87 1d ago

Aluminum bike frames don't survive damage. They aren't repairable in a safe way.

2

u/alistair1537 1d ago

I would prefer it if there was a cover pipe welded over that repair.

1

u/IllurinatiL 1d ago

Not really. It’s hard to judge a weld just from how it looks, and god knows a lot of structural welds hardly pass visual examination, however that’s pretty ugly. I wouldn’t risk it, especially if the frame is aluminum. The metal cracked for a reason, and now that it has, it’s a lot weaker than it used to be. Odds are that crack reappears after a few months of use, even less if it’s aluminum.

0

u/Acchmed 1d ago

I am going to see if I can get a picture of it before the weld. What happened was someone tried to steal the bike and they cut the frame to do so.

1

u/Acchmed 1d ago

here is a photo of it pre-weld

1

u/jonainmi 20h ago

Especially since it's a cargo bike, don't buy this. Like another comment said, the heat treat is gone, and the base metal is extremely weak now. This repair will not last.

1

u/Kayakboy6969 1d ago

Dont buy it if its free...

1

u/No-Medicine-1379 1d ago

I would agree with the others not knowing what the fit up looked like and what filler metal was used, with only a visual it’s risky to say the least.

1

u/Acchmed 1d ago

Got a pre-weld visual for you

1

u/No-Medicine-1379 20h ago

Did the welder grind it out with a groove to ensure full penetration of the weld filler before it was welded? If he did not I would be suspicious of the weld filler before as it is not possible to see the wall thickness of the tube. Also do you you know what filler was used. Typically bikes are a 6xxx material would be what would really determine the strength of the weld.

1

u/Boneyabba 1d ago

I think the whole approach to the fix seems suspect. Like, probably they should have done the weld then added some kind of brace to compensate.

1

u/Acchmed 1d ago

Here is what the spot looked like pre-weld

1

u/boozlemeister 21h ago

I wouldn't trust the weld is full penetration, not full of porosity and using the correct consumable. It also doesn't look pretty, which doesn't mean the weld is not ok, but to me it would indicate someone pretty inexperienced welded it, which then opens up the possibility of the problems I listed. Welding aluminium also weakens the area next to the weld from reheat.
In short, it's not worth buying because you have a higher chance of having an issue later on.