From the 1991 Dodge Viper’s three-spoke wheels to the 2020 Alpina B7's 20-spokers, there are lots of options when it comes to the number of metal bits radially connecting a wheel’s lug hole-containing centre disc to its outer barrel. But a spoke count you don’t see outside of steering wheels is “one,” so in move that can only be described as ingenious, a Russian man hacked all but a single spoke from his alloy wheels to see what would happen.
This comes from the world’s number one source for absurd automobile-related experiments, the YouTube channel Garage 54, whose Russian host, Vlad, had three different aluminium wheels sitting around his shop. Seeing no reason to keep them, he decided to use a marker and an angle grinder to slice off a bunch of spokes to see how the wheels would fare with with a little bit of structural support missing.
In the video, he cuts the five-spoke wheel down to three-spokes, the eight-spoke wheel down to four, and the 16-spoke wheel down to eight. He then bolts the alloys to an old Lada, drives the crap-can through some muddy potholes, and find that things work out just fine. The wheels don’t break, and really don’t seem to deform much during driving.
So then Vlad’s team takes the wheel with eight thin spokes down to four, and both the rim with four skinny spokes and the one with three thick-ish spokes down to two. Even then, the Lada manages to blast through some ruts without destroying the wheels and ejecting the barrel-mounted tires.
From there, the next step was to cut two of the four thin spokes from one rim, and then turn the remaining two-spoke rims into one-spoke rims. The result isn’t particularly surprising: All the remaining spokes experience lots of torsional deflection as the centre disc’s axis rotates about them and out of alignment with the barrel’s axis. Eventually, a one-spoke wheel on the front of the car where most of the weight is breaks in tension.
To help provide a bit more of an understanding of the loads that a wheel experiences as a vehicle drives down an uneven road and around corners, I conducted a cursory Google search of Finite Element Analysis models on automobile wheels, but admittedly, I didn’t find any particularly clear and concise sources. Still, just looking at a single-spoke setup, you can imagine that, as the road acts upon the wheel through the tire’s bead seats, and counters the vehicle’s weight acting through the lug holes of the centre disc, the spoke will experience compression, tension, shear, and bending stresses as the wheel rotates.
The torque through the driven wheels, and rolling resistance will create other loads, plus there are other dynamic loads acting along the axis of the wheel during turning, which could create bending and torsional stresses in the spoke. And of course, fatigue.
And that’s not even considering the stresses in the barrel. Clearly, I’m no expert on wheel design, but even without a nice, descriptive FEA model showing stresses on a wheel in various driving conditions, it’s obvious to me that wheels are under constant assault from a hodgepodge of stresses conspiring to do whatever it takes to break metal. So it’s no surprise this one-spoke wheel failed, though the surprise, I think, is that it lasted as long as it did.