Tire pressure influences performance on two levels:
Grip: When it comes to tires, the area of contact of the tire with the surface and the grip provided are related, i.e. if a tire has the right amount of pressure allowing the entire width of the tire to make contact with the surface that it is rolling over, the steadier the grip of the tire will be, conversely an over-inflated tire is likely to roll only on the central strip, and hence not have a good grip of the surface.
Rolling resistance: Rolling resistance is how much friction occurs between a tire and the surface i.e. more friction leads to more rolling resistance. Both under-inflated and over-inflated tires tend to provide too much contact with the surface, and hence an increased rolling resistance. This can affect one’s energy levels and overall performance as one may find themselves pedalling with great difficulty without yielding significant results or speed. For an optimal grip and rolling resistance it is necessary to get the correct tire pressure based on the kind of bicycle you ride, your weight and your tire type.