Widening Wheels: It’s A Trap!

Photo © Rim and Wheel Works, Inc.

"Can you widen my wheels?"

[I seem to get this call about twice a month. It can go only one of two ways. Usually it goes very well, but every once in a while it can go brilliantly wrong. Let's listen in:]

"No, sir."

"You can't?"

"I won't, and I strongly recommend that you not try."

"Why not?"

[Because you seem to be a nice guy, and I have no reason to want you dead. Yet.]

"Because it's hugely unsafe. Look, what you're asking is for me to saw your wheels in half parallel to the barrel and then weld in a piece of metal between the two halves. That means we would be welding a joint where the two edges simply press together, with no lateral support at all. That might be good enough to hold air if we're just talking about a show car that never, ever gets driven anywhere, but almost any kind of real road impact would destroy the wheel."

"But I need my wheels widened!"

"I'm sorry, but what you need are new wheels. There are also considerations of how much wheel can fit in your wheel well without scraping against the suspension. It's kind of a complex issue, but we would be glad to work with you and set things up right."

"Do you know anyone who would do it?"

[If I knew anyone who was willing to do it I wouldn't trust them.]

"I don't think you're fully understanding me here: Imagine if I took two pencils and glued them together eraser to eraser.

If I just press straight inward, that joint will take lots of pressure. But if I take one finger and push anywhere at a 90-degree angle to the joint, it takes almost no pressure at all to break the glue. That's called shear force. It's like that with welding a joint all the way around the barrel of your wheel - one good shear force impact at 90-degrees to the weld, like a pothole or a raised manhole cover, and the weld will fail catastrophically.

That will let all the air out of your tire in half a second and can potentially kill you or someone else. It basically adds two gigantic glaring failure points to your wheel."

[Sometimes, if the caller seems particularly hip, I'll try for geek humor:]

"It's like putting in an exhaust port on your Death Star that leads straight to the reactor but only beam-shielding it."

[Yeah, fine, but when it works, it works well. Most of the time by this point the person on the other end of the phone understands that what he wants is unwise, and all is well. Sometimes, however, the caller feels the need to push, as if by convincing me of his great need to do this we can somehow conquer physics together, and this is where things start to go amusingly wrong. One of my favorite calls was the teenager who half-wailed:]

"But what if I don't care?"

"Um... we do?"

[However, nothing beats the older gentleman who cheerfully informed me:]

"That's all right - I'm going to be selling the car!"

[Wait, what? Seriously?]

"I'm sorry sir, we really can't help you. Thanks for calling."