Bike tire pressure: what’s fastest on real roads

The evidence here is moderate: real tests, but not many of them. 13 sources, listed at the end.

What the tests say

Two separate losses decide the “fast” pressure. The first is casing loss: a tire that deforms more wastes more energy. On a smooth steel drum, higher pressure always wins. Bicycle Rolling Resistance (BRR) measured a 25mm Continental GP5000 (butyl tube) at 14.2 W at 60 psi and 10.0 W at 120 psi (one tire, 28.8 km/h, 42.5 kg)³⁴. But a drum leaves out the rider. On real pavement, a harder tire passes more vibration into the bike and body, and that energy is lost too. SILCA calls this “impedance”. Others call it “suspension losses”¹¹³.

SILCA’s field tests used the Chung (virtual elevation) method with a 190-lb rider-plus-bike system on 25mm GP4000s II tires. They covered milled pavement, chip seal, and fresh and aged asphalt. Total resistance fell as pressure rose only up to a “breakpoint pressure”. Above it, impedance took over and losses climbed steeply¹. The practical finding is the asymmetry: in one test on new asphalt, being 10 psi below breakpoint cost about 1 W, while being 10 psi above cost about 9 W². Rene Herse/Bicycle Quarterly, who sell wide tires, report similar results¹³.

Independent but small studies support the mechanism, not the exact numbers:

• Model. Turner’s 2024 model treats rider and bike as a mass-spring-damper system. Roughness resistance scales with the road roughness index squared, divided by vertical compliance. On moderately rough roads it exceeds rolling resistance, and only on the best roads can it be ignored⁶.
• Thesis. A 2026 TU Delft master’s thesis measured a rider on a 3D-printed brick-like surface. At 30 km/h, roughly 64% of the 234 W total loss was vibration. On that fairly smooth surface, pressure (3.5–5.5 bar) had only a small effect, and there was no clear optimum at low speeds⁷.
• Small study. A 2025 accelerometer study found lower pressure and wider tires both reduced vibration at the bars and seatpost, though speed mattered most¹².

What moves the answer. Heavier systems and rougher surfaces lower the breakpoint, and wider tires need less pressure for the same support². Frank Berto’s classic rule targets about 15% tire drop (how much the tire compresses under load). For a 200-lb rider plus bike, his chart gives about 136 psi for 19mm, 88 psi for 25mm and 60 psi for 32mm tires. It assumes a roughly 45/55 front/rear weight split, so about 10% less up front and 10% more at the rear⁸. In BRR’s tests, going from 32.5 to 52.5 kg raised Crr (the rolling resistance coefficient) by 10.4% at 60 psi but only 4.4% at 100 psi⁵.

Calculators. SILCA’s calculator takes system weight, tire width, tire type and one of 10 surface categories². SRAM/Zipp’s adds casing type, rim type (hooked or hookless) and inner rim width, and gives separate front and rear figures⁹.

Grip. Lower pressure also helped grip. On 28mm road tires, BRR’s wet-grip coefficient rose from 0.69 at 108 psi to 0.78 at 54 psi¹⁰.

Desert angle. BRR measured rolling resistance falling an average of 17.6% as tire temperature rose from 20°C to 40°C¹¹. Heat also raises pressure. By the ideal gas law (our calculation, not a cited test), a tire set to 60 psi at 21°C would read about 65–66 psi if the air inside reached 43°C.

The numbers

• About 1 W lost when 10 psi below breakpoint vs about 9 W when 10 psi above (one SILCA field test on new asphalt, 25mm GP4000s II tires; manufacturer data)¹²
• 25mm GP5000 (butyl tube) on a drum: 14.2 W at 60 psi vs 10.0 W at 120 psi (single tire, 28.8 km/h, 42.5 kg load)³
• BRR figures are for one tire. For an 85 kg rider plus bike, real-world rolling resistance is roughly double the published values⁴
• About 64% of a 234 W total loss was vibration at 30 km/h on a brick-like surface (TU Delft thesis, one rider)⁷
• 15% tire drop for a 200-lb rider plus bike: about 88 psi (25mm) and about 60 psi (32mm)⁸
• Going from 32.5 to 52.5 kg load raised Crr 10.4% at 60 psi but only 4.4% at 100 psi⁵
• Wet grip coefficient on 28mm tires: 0.78 at 54 psi vs 0.69 at 108 psi¹⁰
• Average 17.6% lower rolling resistance at 40°C than at 20°C tire temperature (six tires)¹¹

Myths and disagreements

• “Harder is faster.” That’s only true on very smooth surfaces. Drum tests show it³, and SILCA’s calculator starts at 187 psi for good 20mm tires on a wooden velodrome². On normal roads, impedance flips the result¹⁶.
• “The number on the sidewall is the target.” It’s a maximum, not a recommendation. Calculator outputs are usually far lower²⁹. Hookless rims have their own hard limit (see).
• Disagreement: how sharp the breakpoint is. SILCA’s dramatic asymmetry comes from a manufacturer’s own field tests¹². The TU Delft thesis found pressure had little effect on its smoother surface⁷. The penalty for overinflating probably grows with how rough the road is.
• “Front and rear should match.” The rear wheel usually carries more weight, so Berto’s method and both calculators give a lower front pressure⁸⁹.

How to pick your tire pressure

• Enter your total weight (rider, bike, bottles and bags), your measured tire width, and the roughest surface you ride regularly into the SILCA or SRAM/Zipp calculator²⁹.
• If you’re between two numbers, choose the lower one. Stay within the rim and tire minimums, and above the point where you start getting pinch flats or rim strikes².
• Run the rear a few psi higher than the front, roughly in line with a 45/55 weight split⁸.
• In Phoenix summer heat, check pressure just before you ride, not when the bike has been sitting in a hot car or garage. Pressure rises as the air warms (gas-law estimate above)¹¹.
• Test it yourself: ride the same rough segment at two pressures a few psi apart and compare comfort and speed. The calculators say their output is only a starting point²⁹.

Sources