Cars and motorcycles typically use tyre pressures of 30-40 PSI.
By the standards of literally almost every non-car non-motorcycle type of vehicle that uses pneumatic tyres, this is ridiculously low:
- Truck tyres are typically inflated to 80-150 PSI (depending on the truck and the tyres).
- Aircraft tyres routinely go up to 200 PSI.
Now, both of the above could be justified as needing higher tyre pressure to compensate for a heavier vehicle, but...
- ...bicycle tyres are typically inflated to the 60-100-PSI range (with the exception of specialized fat-tyre bikes for use on loose snow, which use tyre pressures in the typical car/motorcycle range)!
Higher tyre pressures minimize tread deformation and sidewall deflection under load, which is advantageous in multiple ways:
- Since the tyre isn't squashed as far out of round as it would be at a lower pressure, less energy is wasted in continuously squashing it in new directions and unsquashing it in old directions as the tyre rotates; this decreases the tyre's rolling resistance, making it more efficient.
- The reduction in deformation under load reduces the amount of mechanical fatigue damage incurred by the tyre as it continuously bends and unbends, increasing the tyre's lifespan and decreasing the chance of failure in a given timespan.
- The reduction in deformation under load also reduces the amount of heat generated as the tyre flexes, dramatically reducing thermal degradation of the tyre material, and, again, increasing the tyre's time-between-failures.1
So why do cars and motorcycles still use low-pressure tyres?
1: On the flop side, driving with underinflated tyres dramatically increases heat generation and thermal damage. (This is why it's not safe to drive with a flat for any length of time - such a tyre will produce so much heat when rotated that it can be counted on to disintegrate violently in a very short period of time.)