Is it a crack or ???

orezok · Sep 28, 2019

I was airing up the tires on my B7800 and notices this on my rear wheel. Thoughts?

jones6780 · Sep 28, 2019

All I see is a weld with a little undercut. Point to what you see.

orezok · Sep 28, 2019

jones6780 said:
All I see is a weld with a little undercut. Point to what you see.

Heres a better image with annotation. The other 5 areas the paint is smooth over this area.

oosik · Sep 29, 2019

I see a spot where somebody welded on the rim to make a repair. Rust or ??? Is this tire going flat on you? Soapy water on this spot to check for air leaks. If it's leaking here - instal a tube. Otherwise - maybe a new core in the stem.

The other five areas - ???? There are six "welded tabs" on this rim - ??? Check them all with soapy water. If this tire is already tubed - could be that one of the welded tabs is sharp on the inside and has cut the tube.

radios1 · Sep 29, 2019

this pitted weld is the kind you get if you don't clean the metal properly first.

orezok · Sep 29, 2019

oosik said:
I see a spot where somebody welded on the rim to make a repair. Original factory weld Rust or ??? Is this tire going flat on you? Soapy water on this spot to check for air leaks. If it's leaking here - instal a tube. Otherwise - maybe a new core in the stem.

The other five areas - ???? There are six "welded tabs" on this rim - ??? No, three on each wheel Check them all with soapy water. No leaks yet. If this tire is already tubed - could be that one of the welded tabs is sharp on the inside and has cut the tube.

. I dont think the crack goes through the rim, just between the rim and the hub. I plan to chemically paint remove some of the paint to see the virgin metal, but I didnt want to do that until the comments were received.

5030 · Sep 29, 2019

All I see is a porous weld caused by mis-application of a MIG gun. If it was mine, I'd gouge out the weld and re-weld it (of course removing the tire and tube first).

rScotty · Oct 1, 2019

orezok said:
Heres a better image with annotation. The other 5 areas the paint is smooth over this area.

View attachment 622906

With a picture of the whole wheel shiowing all the welds I could help more. As is, I'm not understanding exactly where on the rear wheel this weld is? and why there are another five similar welds? But if those six welds are part of the normal wheel manufacture and if they are better.... and if they don't involve the tire rim or tube area too much..... then on something light like the B7800 I'd probably just fill those pin holes in with paint and ignore. And here is why...

What I'm seeing is what is called "porosity". When the pin holes are round like that it is most likely caused by poor welding technique instead of contamination.
Sure it could be the result of trying to weld over contamination.... or even of welding something that is wet with water....., but usually when the bubbles look like that it is from welding too hot or with the arc the wrong length. Looking at that weld, It's kinda undercut as well, so I'd say too hot and he/she were trying to keep the arc a little too short.

Both of those are the kind of poor welding mistakes you see in production runs where they are trying to weld as quickly as possible. Too hot, too short, too fast.
You can grind it out and reweld, but that's a hassle, and it probably isn't necessary. Especially if the rest of the wheel is good. Truth is that most welds have some porosity, even if it is microscopic. That much in the photo is a bit too much, but porosity doesn't necessarily mean the weld is weak - just that it could have been much better.
A porous weld without cracking is still stronger than the adjoining area that doesn't have any weld at all.

BTW, If you ever do want to make crappy welds like that look good, it's easy to do by just grinding out the porosity and welding it again.
It's even easier when doing oxy/acetylene or TIG welding and there's a reason you don't often see porosity with oxy/acetylene or TIG welds. That's because using those techniques you can go back and remelt the weld itself as deep as you want. Then, by playing with the heat a bit and chasing the molten metal around you can cause it to flow & harden with a smooth surface without adding additional metal....or at least not much...just enough to make the surface smooth.
rScotty

5030 · Oct 1, 2019

I would not be at all surprised if those welds are robotically applied.

Egon · Oct 2, 2019

Angle grinder and new weld would work.

nyone · Oct 3, 2019

Looks like theres alot of porocity in that weld. Between that and the edge like that i would grind and reweld it.

rScotty · Oct 3, 2019

nyone said:
Looks like theres alot of porocity in that weld. Between that and the edge like that i would grind and reweld it.

I'm still not sure what the rest of the welds look like. That might change things But I'd probably leave it alone. After all, the OP says here are 5 more & better welds.
With grinding it out and re-welding, what do you gain besides a better look to the weld surface?

Most of the time, porosity is largely a surface feature. I'm also thinking that the same errors that make porosity happen on the surface of welds are the very things that make for a better deep weld & more penetration.

All that said, if it were mine and I'd done the welding I'd have gone back over it to reflow the surface when it was first welded.
rScotty

arkydog · Oct 3, 2019

keep an eye on it and drive it like you stole it.

ArlyA · Oct 3, 2019

Looks like poor welding to me.... but to take it all apart and re-weld it when its not cracked for sure?? As arkydog says "keep an eye on it"

KevinThatcher · Oct 5, 2019

First, clean the parts of the vehicle properly then check for the damages.

LD1 · Oct 5, 2019

Its a little B7800. If there are indeed FIVE other GOOD welds on that rim/hub....leave it alone. Heck if that weld wasnt even there it wouldn't be a problem.

rScotty · Oct 5, 2019

LD1 said:
Its a little B7800. If there are indeed FIVE other GOOD welds on that rim/hub....leave it alone. Heck if that weld wasnt even there it wouldn't be a problem.

Agreed.

orezok · Oct 5, 2019

Yeah, I think wait and watch is the way. Thanks for your guys input.

Gary Fowler · Oct 5, 2019

I really dont see porosity. What you are seeing is weld splatter that should have been cleaned off prior to painting. It could just be undercut at the toe of the weld and only way to be sure is to lightly grind the area to remove the possible undercut and then examine. I would also be concerned with the vertical crack line in the picture. I would grind that area slightly also to remove the paint and examine it. The only sure way to tell is to do a dye penetrant test on the area (after cleaning away all the paint and weld splatter. But if the crack is large, cleaning with a light grinding should still show the crack line. If you dont see a dark line after grinding, I would just repaint the areas.
If it is a crack, it needs to be repaired so it doesn't get worse. This would entail removing the tire to do it though.

SmallChange · Oct 5, 2019

As far as the thin rusty line at the outer edge of the weld, I'm not sure, but I thought it was a crack in the paint, not metal. Grinding down into that crack with a small Dremel style tool and a cutoff abrasive wheel - that is, grinding a short groove something like 1/16" wide and half an inch long - would resolve that question, and leave practically no damage after a touchup.

If you're all sure, well, then, never mind.