Why do commercial trucks have convex and concave wheels? | Hacker News Reader

Why do commercial trucks have convex and concave wheels?

jalopnik.com

41 pointsThinkingGuy18 comments

This article made it so close to teaching me something, except it just confused matters more haha.

I think what they're saying is a wheel on the front that's like this [| will have wheels on the back that look like this |][|

Yeah, that's it. Wheels are ] shaped, so if you flip one around you can bolt a pair together into a double wheel ][.

Your sentence surmised it perfectly!

https://www.theautopian.com/heres-why-car-wheels-are-so-flat...

This article stated many things in several paragraphs, but did not explain why at any point. Why are the wheels flipped? Why does that improve the geometry?

A more accurate headline is “trucks don’t have convex and concave wheels: they are all the same”

I stopped reading such kind of articles. Every paragraph starts similar and one reads in in the hope for some new or additional information only to realise at the end of the paragraph that same was said in different words. All the while I was scrolling past ads that get wedged in between the paragraph lines... Skip ...

Even with ad blocking enabled it's a new low for webcontent.

I was hoping it would be a reference to the parabolic cross-section rule as key for achieving supersonic velocity.

They aren’t all concave or convex.

What the article describes are either Unimount (hub piloted) or “Budd” (stud piloted) wheels.

There are also Dayton wheels, but these are increasingly rare.

What does 'hub piloted','stud piloted', and 'Dayton wheels'?

I figured I'd share my research by writing it up... except that toward the end of my research I found conflicting information. And I don't feel like researching more so I'm just going to post as is with pointers to the conflicts.

the wheel is the rubber-tire+metal-rim, the thing you take off when you get a flat tire.

It is mounted to the car/truck by bolting it onto the hub, which is the part of the truck you attach wheels to, the thing that contains the brakes. (and btw, let the rest of the internet know that these are not "breaks")

when you mount a wheel onto a hub, you have lug nuts holding it on. You might have noticed on a passenger car that the underside of the lug nuts have a sort of hemispherical shape such that screwing it on seats and centers the nut into a corresponding dish on the wheel. This (once all the lug nuts are seated) aligns the center of the wheel with the center of the hub. That's the stud-pilot system, the studs do the piloting (centering) also called with a brand name(?) Budd.

There is also a hub-pilot system, where the wheel is automatically centered on the hub because the hub is essentially conical. In this case the lug nuts just bolt on and don't participate in the piloting.

that information came from here https://buytruckwheels.com/pages/hubpilotvsbudd

one type of Dayton wheels is another hub-piloting system, but with one big center screw instead a collection of lug nuts. You have seen these mostly on 1950's style sports cars with flashy wire-spoked wheels and that "flying wing" nut in the center holding the wheel on. https://www.daytonwheel.com/

But I guess that's just for cars, because there is another Dayton wheel for trucks. It is a large metal piece that is something like spokes, but just 5 or 6 big ones and the wheel gets bolted on to the tips of that "star" hub. You can look at the pictures here https://thecampingadvisor.com/dayton-wheels-vs-budd-wheels/ But you'll notice that they also have pictures of the wire spoke style dayton wheel.

I think that's just a crappy website, but I've put enough effort in. YMMV, literally :)

This is something the article doesn't mention, but we learnt in our early teens helping to fit wheel nuts, and of course they look better dome side up.

Loading is probably where I would start - we can take the 40ft container maximum load(capacity+container) as 29tons, divide by 8 to give 7250 lbs.

I discovered tires have 2 load ratings, 150/149 would mean 7400lbs in single configuration, 7150lbs in double. So there is a little inefficiency in concatenated configuration.

Google easily finds me 40' 4-axle trailer. Same company provides similarly 2-axles with the wheels doubled up.

https://www.cheetahchassis.com/containerchassis/40-lightweig...

"if you want to maximize your capacity for certain applications" ..the 'why' still is not answered.

Best I can come up with is the 4-axle config creates tire scuffing (so cost), more axles = more friction = fuel cost. And worse handling.

(But cost is a good thing, if you're marking it up & charging the customer right? - not sarcasm, it's from the link)

This method of wheel concatenation is also used by pickup trucks known as a “dually” for commercial, farm/ranch and recreational use. The same wheels are often used in front and rear axles even if only the rear tires are mounted in pairs. This is presumably done for cross compatibility and/or tire rotation.

https://www.jdpower.com/cars/shopping-guides/what-is-a-duall...

> wheel concatenation

Actually laughed out loud at that phrase. Touche!

I was hopeful that would be an audience context sensitive description. In my mind a dually concats, something with multiple axels appends wheels, examples being the Tyrrell P34 or 6x6 Gelandewagon.

https://en.wikipedia.org/wiki/Tyrrell_P34

https://en.wikipedia.org/wiki/Mercedes-AMG_G_63_6x6

This article is terrible. Well it's more the adverts on the website I can't judge the article quite.

I'm scrolling and moving ads out of the way so much I keep forgetting what it told me.

The article seems to say the front wheels bulb out to hold stuff, but why do the back wheels go the other way?

I think the implicit reason (which I too wish the article would state) is that if you (1) have bowed-out wheels for the front, and (2) want the benefit of all wheels being the same (easy replacement, etc), and also (3) want more wheels on the back (because that's where the load is), then the arrangement of bowed-out-face bolted to bowed-out-face solves it.

If you had a bowed-out-face on the rear wheels, you would need some comically long bolts to join it with the other (inner) wheel.

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