(Eli5) Why do Buses & Trucks use 2 skinny wheels put together on each side of the axle? Instead of just using one fat wheel?
In: Engineering
If you look up “wide base tires” One fat tire is also an option. I see it in mexico a lot, I’ve been told they do better on washed out roads, but the guy that told me that isn’t a truck driver…. and doesn’t own a car.
To add; when a bus or truck turns two wheels aren’t damaged.
A small circle has less distance to go than a large circle around the same point. This means on tyres one edge has to travel further than the other while rotating the same amount; the solution is one side drags.
On thin tyres the dragging is minimal, but on a large tyre the edges will get dragged every time they turn a corner meaning it wears out faster and stops the vehicle from turning well
Because it’s easier to make it flat that way.
Anything pressurized wants to be round, but tires work best when they have a nice flat surface to meet the nice flat road. This problem gets worse as the tire gets bigger. That’s why your bike tire can basically have a circular cross section and it’s not big deal, it just squishes some as you roll on it. But if you do that with a really big tire at speed all that flexing in the sidewall generates a lot of heat and the tire fails.
A truck or bus is so heavy that you need a tire about about 2 feet wide to provide enough surface to take the weight from the axel, but a single tire 2 wide will bulge out way too much. Two skinnier tires side by side has almost as much surface but doesn’t bulge nearly as badly because you have a sidewall in the “middle” to hold everything down.
You also have the advantage that if one goes flat the whole wheel doesn’t drop.
Not Five Explanation: Trucks and buses generally have double wheels at the back to increase the area of contact on which their weights acts and hence reduces the pressure on the ground. It also provides the ability to replace one side if it is punctured, as well as being more cost friendly.
Five Explanation: two wheels is more stable, two wheels is cheaper than big fat wheel, two wheels is easier to replace if one side is broken. two wheel good.
Edit: Listen, I haven’t talked to a kid in years. I don’t know how smart they are.
Some trucks run super singles, it’s basically one big tire instead of two smaller ones. Every trucker I’ve talked to that has them absolutely hate them. I guess they are horrible on ice and snow
despite what you may think its actually the air pressure in the tire that holds the weight and not the rubber itself. to hold more weight you can increase pressure, but a single tire can only hold so much pressure safely. this is where adding more tires comes in
each tire is rated to hold a specific amount of weight at a specific pressure, so if you need to hold more weight you add more tires.
Probably because of tire explosions. If only one of the two skinny tires blows up, it’s a smaller explosion and easier to replace than one big tire.
Here’s something that no ones added yet,
All the individual double wheels and front wheels on buses and trucks are actually identical and the outer double wheel is just flipped around, which is why the rear wheel looks concave and the front wheels look convex. This means that they can all be easily rotated and replaced, and you can theoretically pull a rear wheel off to replace a flat in the front and still have plenty of wheels left to drive on.
Please note that there are many trucks that do use single fat tires rather than skinny tandem tires. There is a lot of science in the world of pavement-tire interaction and the “fat” tires are increasingly being used these days.
Rudundancy. If one wheel goes flat or blows out the vehicle still remains stable. As well it is added traction at the drive wheels. That much weight on the wheels causes greater wear, by adding more tires it spreads that weight reducing wear.
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