Tire pressure affects more than just rolling resistance. Getting it right can improve your aerodynamics in ways most riders overlook.
The Connection
Tire pressure determines tire shape. Shape affects how air flows around the tire-rim interface. This matters more than many realize.
Over-inflated tires create a narrower profile but can actually increase drag by disrupting smooth airflow over the rim.
Finding the Sweet Spot
Modern wide rims work best with lower pressures than traditional setups. Most riders run too much pressure based on outdated recommendations.
For 25mm tires on 21mm internal width rims, try 75-85 PSI front and 80-90 PSI rear for a 70kg rider. Adjust based on road surface and conditions.
The Evidence
Wind tunnel testing shows optimal pressure creates the smoothest tire-rim transition. This can be worth 2-4 watts at typical speeds.
Combined with rolling resistance benefits of proper pressure, getting this right is one of the easiest free speed gains available.
