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Comment by SoftTalker | Hacker News Reader

But more tires, more tire wear, more micro-plastic pollution from the tire wear, etc.

Nope. Twice the number of tires means half the weight per tire. Half the weight means 1/16 of the wear per tire. Twice the number is 2X, so overall 1/8 the impact.

Any reason why we don’t put as many tires on (existing) trucks as possible? Seem like a good deal reducing tire wear.

It will complicate the control of the truck and add more components (increasing the cost).

Truck drivers don't have to pay for the negative externalities of tire wear

It would probably increase wear, not decrease it. When a vehicle with more than one non-steering axle turns, some of the tires must slide. It's mostly not too noticeable unless the corner is fairly tight or the trailer has at least three axles. You don't really want any more wheels on the ground than you need to support the load. Or you need to allow those axles to pivot.

Heck, even with my modest two-axle travel trailer I leave tire marks on my driveway where I have to turn sharply to get it onto the road.

Increased friction -> uses more gas/energy. Complicated the mechanical design; more moving parts you have to maintain in a more crowded area.

I think we need to look at it as a throughput question. How do we transport X tonnage from pt A to pt B? What’s more efficient? One truck with more axles or two separate trucks, with fewer, for example; taking into consideration roadwear, tire wear, bridge capacity, etc.

Fewer vessels for fewer total trips is the more efficient option as a rule. See: cargo trains and gigantic container ships. Australia has some super long cargo trucks they allow called road-trains, I think, which are justifiable if you can fit them onto roads.

The thing that needs to be balanced in the case of # of axles is the cost of outfitting each truck with additional axles and associated suspension/braking hardware versus the savings in tire costs due to reduced wear on the larger number of tires.

I wanted to add that there are a bunch of factors at play in this optimization problem that might not be obvious. For example, there are diminishing returns in reduced wear from distributing load over more tires at some point. More tires & rolling parts also tend to increase rolling resistance, even ignoring extra weight that tends to come with a more complex design. Another potential advantage of having more axles is to reduce the frontal area of the vehicle by arranging tires in the direction of travel instead of putting them side by side on the same axle. Frontal area is a big component of the drag on a vehicle, along with speed and drag coefficient.

Probably a train. Doesn’t even need to carry its own electricity source.

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