Why don’t they make airless car tyres?
Humwee NPT from Resilient Technologies and Wisconsin Madison research center on polymer engineering.
Also Michelin does them.
Airless tires have the advantages of
- Being pierce proof
- Lasting more, so fewer replacements are needed
- No need to inflate them
- Maintenance free
- Higher weight to have same amortization.
- Not suitable for high velocity, very noisy.
- Cost more to make.
- Vulnerable to freezing and mud
- Ride height and load can’t be adjusted
So you will see them in forklifts, golf carts and lawnmowers, but not in consumer cars.
Consumer cars have already air tires which are resistant enough to piercing, so as long as you drive in clean road and replace them before they wear too much, they are safe and reliable.
Higher cost is balanced by longer lifespan and ruggedness, which makes them ideal for rugged vehicles. Freezing and mud aren’t a problem in hot deserts or regular roads.
Filling void with foam is also a valid way to seal the wheel, as adopted by the Mars rover.
Air tires can be adjusted through lowering or raising the internal pressure. This can’t be done with airless tires, but it is a marginal drawback as air tires are made for have best performance in a narrow interval of pressure. Even tough, this is very relevant for trucks, were a slight more efficient tire is worth it in terms of safety and fuel savings.
Modern air tires do not explode when pierced, the hard rubber keeps the spike inside, or seal the hole with sealant agents inside. Having said that, they are relatively vulnerable on the sides so tyres often blown when rubbing up against the pavement/sidewalk.