Road Bike Tire Width: 25mm vs 28mm vs 32mm Comparison

Road bike tires come in various widths, each offering different performance characteristics. Tire width affects comfort, rolling resistance, aerodynamics, and grip.

Quick Answer: 25mm tires dominated road cycling for years, but 28mm tires now offer better overall performance. Wider tires (28-32mm) provide improved comfort and grip with minimal speed penalty. Rim width and frame clearance determine maximum tire size.

The Evolution of Tire Width

Professional racing once mandated narrow 19-21mm tires. Testing proved that wider tires at lower pressures actually roll faster while providing better comfort. Modern road bikes accommodate 28-32mm tires, with many gravel-capable frames fitting 40mm+.

Width Recommendations by Use

• Racing/criteriums: 25-26mm for aerodynamics and responsive handling
• Training/sportives: 28mm balances speed and comfort
• Endurance/touring: 30-32mm maximizes comfort for long days
• Rough roads: 32mm+ reduces vibration and pinch flat risk

Tire Pressure Guidelines

Wider tires run at lower pressures than narrow tires. The larger air volume provides suspension while maintaining low rolling resistance. Over-inflating wide tires actually increases rolling resistance by reducing the tire’s ability to conform to road surfaces.

A 25mm tire might run at 100-110 PSI, while a 28mm tire achieves better performance at 80-90 PSI. Rider weight influences optimal pressure—heavier riders need more pressure, lighter riders less.

Rolling Resistance Reality

Contrary to old beliefs, wider tires don’t automatically roll slower. At correct pressures, 28mm tires often roll faster than over-inflated 23mm tires. The key is matching tire width to pressure for optimal contact patch deformation.

Tire compound and construction affect rolling resistance more than width alone. A quality 28mm tire with supple casing rolls faster than a cheap 23mm tire with stiff casing.

Aerodynamic Considerations

Tire width affects aerodynamics, but the impact is smaller than most cyclists assume. At typical riding speeds (15-20 mph), aerodynamic differences between 25mm and 28mm tires cost mere seconds over long distances.

Matching tire width to rim width matters more for aerodynamics. A 28mm tire on a 19mm internal rim creates smoother airflow than a 23mm tire on the same rim.