Tire pressure and vehicle handling

Low pressure adds passive per-wheel braking while the vehicle coasts. The penalty reaches zero at 20 PSI for Old tires, 25 for Normal, and 30 for Modern; higher pressure does not add a traction or performance bonus in the traced path.

Pump targets

Inflating requires a Tire Pump; deflating does not. The vehicle menu fills to the tire’s normal target, then offers a second fill five PSI higher.

The normal targets are 30 PSI for Old tires, 35 for Normal, and 40 for Modern. Those values keep a ten-PSI buffer above the point where the pressure penalty begins.

What the physics applies

Below the threshold, the vehicle adds pressure-derived brake input to each affected wheel. In the traced physics path this acts as extra rolling resistance while coasting; the effect grows as pressure falls and with the current speed factor.

Pressure and tire friction are separate inputs. No pressure-derived traction bonus was found, and pressure was not shown to change engine force. Tire quality, condition, road surface, forest and rain can still affect friction through their own paths.

Very low pressure

With the engine running above 10 km/h, pressure below 5 PSI enters a pressure-dependent tire-removal check. At 0 PSI, the qualifying update removes the tire unconditionally and drops the item by the vehicle.

Tire condition is a separate failure system. Low condition has its own removal chance, and pressure is not used by the traced tire-wear calculation.

The second inflation option adds five PSI above the normal target. That extra pressure is not needed to avoid the low-pressure braking penalty.