Wouldnt a solid rubber tire do the same job with no risk of punctures?
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Heat. The answer is heat, thermal gradients would destroy a solid rubber tire in short order. Suspension could be softened up to compensate for stiffer (solid) tires, but they do not dissipate heat well.
The first tires were put on wooden wheels and were not inflated with air. The ride was extremely uncomfortable by today’s standards as pneumatic tires (tires that hold air pressure) help absorb impact, similar to your car’s suspension.
As you pointed out, the main problem of pneumatic tires is that they are prone to punctures. Another issue is uneven wear due to over/under inflation and impact breaks from hitting potholes or curbs.
Some tire manufacturers are attempting to move away from inflated tires to airless tires, but it is very difficult and costly to replicate the impact absorption of a pneumatic tires with a flexible, supportive structure.
Check out [Michelin’s Tweel](https://michelinmedia.com/site/user/images/Tweel.jpg).
Michelin makes these for skid steers, golf carts, and other vehicles that cannot maintain a high speed. Another core problem with airless, rigid tires is tire deflection. This is when a fast spinning flexible object deforms at high speed. The core challenge with this is that you have to develop a structure that can flex for ride comfort, but also be rigid to avoid deflection.
rubber is heavy, air is light.
rubber is also significantly stiffer than air, which is a problem that can be addressed with a different suspension philosophy. its the unsprung mass that kills the idea. all that mass on the wheels themselves really dampens engine performance, steering feel, and suspension response times. imagine strapping weights to your hands and feet then going for a swim.
This reminded me of an episode of darkwing duck where he goes back in time to a dinosaur city where they are doing everything backwards. Roads are bags filled with air (constantly being patched) and the tires made of stone. That was a fun episode. Sorry, what were we talking about?
Not sure if anyone linked this already. [They have been working on airless tires for some time now](https://michelinmedia.com/michelin-uptis/). I’ve never seen them IRL but the design helps with the harshness and weight issues people have mentioned. It would be cool to not have to ever worry about punctures, or having to periodically inflate them, or pay for maintenance on tire pressure sensors.
You can compress a gas as much as you want. You cannot compress rubber as much as you want.
There are so many vehicles and use cases that require different pressures that a gas solves more problems. It also provides more cushioning than solid rubber making the ride smoother
A solid rubber tire would significantly increase two undesirable variables, both of which relate directly to both fuel efficiency and ride quality:
1. Unsprung weight — wheels, tires, brakes, etc are all unsuspended components, which means they are below the suspension on your vehicle. The heavier these are, the harder it is to get your vehicle moving from a stop. Takes more power, more gas, more time, and is harder on the drivetrain.
2. Rigidity — If you could get hit in the face with a lacrosse ball or a dodgeball, which would you choose? Dodgeball is a thin rubber shell with a lot of air inside; it might hurt if it was thrown hard, but you’d be fine. Lacrosse ball on the other hand is thick dense rubber to the core and if it hits you in the face at high speed you’re probably gonna need stitches, dental work, and/or a trip to the hospital. Solid rubber tire on a car is a lacrosse ball up your butt, is my point. And nobody wants that.
They cushion the ride better than suspension. People driving with low profile tires have a much worse ride. You feel every bump.
I’ve used solid rubber tires before, and they are really terrible for outdoor uses. Handling in wet conditions is generally awful, and it’s a very rough ride generally. The only cases I’ve seen them used to a benefit have been forklifts in warehouses where the floors are flat and dry.
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