Welding Aluminum Wheels: To Bead or Not to Bead?

Take it to a pro for examination of the crack

2007 Audi S8 wheels

Aaron Gold

To weld, or not to weld, that is the question:
Whether 'tis nobler in the wallet to suffer
The outrageous cost of new wheels,
Or to take arms against a sea of cracking,
And by repairing, end them: to weld, to leak
No more; and by a weld, to say we end
The heart-ache, and the thousand natural shocks
That aluminum is heir to? 'Tis a consummation
Devoutly to be wished...

It's a common question: Should I weld my cracked aluminum wheel? Opinions vary wildly, from “Absolutely!” to “Nooooo!” and pretty much everything in between.

So here's a definitive answer: Maybe.

The Dangers of Cracked Wheels

Aluminum alloy wheels have a tendency to crack if they get hit hard enough. How hard is enough depends on a few factors: how brittle the alloy is, the design of the wheel, and the tire's aspect ratio being the most important. Usually a good deep pothole or raised manhole cover is what does it. Cracks are extremely dangerous, and not just for the obvious reason that they can let the air out of your tire. There's also the fact that they can let the air out of your tire very quickly and without warning.

Even a small crack in a wheel—one so small that it is covered and sealed by the bead of the tire so that the tire is not leaking—still needs to be dealt with, even though it is not an immediate problem. A crack like that is going to grow, and it will usually not even take as hard an impact to widen it as the impact that originally caused the crack. If the crack turns to one side or splits into a “Y” shape, there is the possibility that you could catastrophically lose an entire chunk of wheel.

To Weld or Not?

When deciding whether to weld a cracked wheel, take these important issues into account:

  • The location of the crack: The only type of crack that is even marginally safe to weld is one on the back or inboard side of the wheel. A crack on the front face of the wheel compromises the structural integrity of the wheel, as does a crack on one of the spokes. A crack inside the barrel is also inadvisable to weld.
  • The direction of the crack: Most of the time, a crack on the back side of the wheel will cross the flange and bead area at right angles to the direction the wheel spins. This type of crack can be welded because it can be opened up to accept the weld. A crack that goes parallel to the spin direction should not be welded, because it will usually cause the wheel to become a little wider at the weld area, meaning that the wheel will probably never run straight again.
  • The skill of the welder: Aluminum alloy must be welded with a process called TIG (tungsten inert gas) welding. Aluminum wheels that are MIG (metal inert gas) welded are a disaster. The bead is much thinner and weaker, and the process burns the heck out the surrounding alloy, weakening the entire area around the weld. Wheels should be welded only by an experienced welder who knows TIG welding as well as knowing how to deal with wheels specifically.

Why a Pro Should Handle It

Ideally, the wheel should be straightened before welding. An impact that will crack a wheel will almost certainly have bent it as well, and trying to substantially straighten a wheel after welding stands a good chance of breaking the weld. Most of the time the electrical current used to weld will also warp the wheel very slightly, requiring some minimal truing even afterward, but this is much more easily done if the wheel is straight before the weld occurs.

After the wheel is welded, there will be a large bead of solder to deal with. That bead must be made completely smooth, at least in the area where the tire contacts the wheel, or the tire will be making imperfect contact and will leak. Some shops will grind the bead down and smooth it out on both sides or even smooth the whole area with a computer numerical controlled (CNC) lathe, usually in preparation for repainting or remachining the wheel. Some shops will smooth the outside of the barrel but leave the bead on the inside to make sure the weld stays as strong as possible.

Basically, all this is a very good reason to have your wheel welded by professionals if you're going to have it done at all. Which brings me to the final point to consider—a weld will never, ever be quite as strong as the original material. The vast majority of wheels done professionally will hold up just fine, but there are always some that take a good hit in the same place and pop the weld. Usually those are able to simply be rewelded. However, some will take a good hit somewhere else and crack in an entirely different place on the wheel. There is an element of randomness here.

So this can be a difficult decision, and there are no easy answers. The best option is always going to be to replace the wheel, and in cases where the replacement cost of a wheel is anywhere near the repair cost—say, with a good reconditioned original equipment manufacturer (OEM) wheel—just replace it. In cases of wheels that are either extremely expensive or difficult to replace, welding can still be a viable option, sometimes. Aye, there's the rub...