The right pressure for your tires
Seven questions, your rear and front pressure, and your tire rolling on your road so you can see what that pressure changes.
Tap a tire to see it roll
Your rear tire, rolling
How it's calculated
- The questions are the ones from SILCA's calculator (total weight, surface, measured width, wheel size, tire type, speed, weight distribution).
- The starting pressure gives a 15% tire drop on a smooth new road: the tire compresses by 15% of its width (Frank Berto, “All about tire inflation”, 2006, 50 tires measured). Above 37 mm, Berto's table is extended with the same contact law (pressure proportional to width to the power −1.5). Each wheel follows its own load: 50, 52, 53 or 53.5% of the weight on the rear depending on the bike (SILCA's weight distributions).
- The surface sets the target drop: 13% on an indoor track, 14% on an outdoor track, 15% on a smooth new road, then 15.5 · 16 · 16.5 · 17 · 18 · 18.5 and 19% up to Category 4 gravel (our own setting). On a tire wider than 32 mm, which already soaks up bumps, the gap from 15% is scaled down in proportion.
- Tire type and speed adjust the pressure based on our simulation (half the measured effect, to be safe): very supple casing −6%, mid-range +11%, flat-resistant +18%, butyl tube +21%; from −2% at the slowest speed to +6% at pro level. The drop always stays between 11 and 20%.
- The rolling tire: the wheel and rider are simulated with M. M. Turner's model (“Cycling on rough roads”, arXiv 2405.00019, 2024). The tire is a spring that stiffens as pressure rises, lightly damped by its casing (assumption: 8%), and it can leave the ground. Bike and gear are assumed to weigh 8.5 kg (19 lb) on a road bike, 9 kg (20 lb) on a triathlon bike, 10 kg (22 lb) on a gravel bike and 13 kg (29 lb) on a mountain bike.
- Power lost: the vibration your body absorbs (Turner) plus the rolling resistance measured on a drum by BicycleRollingResistance.com, per tire at 42.5 kg (94 lb) and 28.8 km/h (17.9 mph): very supple 6.7 W (Vittoria Corsa Pro Speed TLR 28), performance 9.7 W (Continental GP 5000 S TR 28), mid-range 17.6 W and flat-resistant 22.0 W with a butyl tube (GP 4 Season 25, Gatorskin 25). A butyl tube adds 16% at 55 psi (3.8 bar) and 29% at 25 psi (1.7 bar) (same tire, same drum, 2014). Resistance goes down as pressure goes up.
- Two widths: if your front and rear tires aren't the same width, each wheel is calculated with its own (its load, its width, its target drop).
- What the tire does: it “hugs the bumps” if it's on the ground at least 90% of the time, it “skips” between 75 and 90%, it “bounces” below that, and it's “too squashed” beyond a 21% drop. “At max” is the usual maximum pressure for your width: 116 psi (8 bar) up to 25 mm, 102 psi (7 bar) up to 32, 73 psi (5 bar) up to 38, 58 psi (4 bar) up to 45, 44 psi (3 bar) up to 55, and 36 psi (2.5 bar) above that.
- Comfort: the vibration at the saddle (rear tire) or the handlebar (front tire), from 100 (3 m/s² or less) down to 0 (40 m/s²).
- Limits: hookless rims are capped at 72.5 psi (5 bar) by the ETRTO standard; also stay within the max pressures printed on your tire and rim; the frame is assumed to be rigid.
Frequently asked questions
Why does the rear tire need more pressure than the front?
Because it carries more weight: 52% on a road bike, 53% on a gravel bike, 53.5% on a mountain bike, 50% on a triathlon or track bike (weight splits from SILCA). Pressure follows the load on each wheel: at 80 kg (176 lb) on worn pavement with 28 mm tires, the tool gives 66 psi rear and 61 psi front.
Are rock-hard tires faster?
On perfectly smooth roads, a bit more pressure saves a few watts. As soon as the road gets rough, an overinflated tire bounces instead of rolling: it touches the ground less and your body soaks up the shocks. The tool's “Side by side” view shows it.
What pressure if my rear tire is wider than my front?
Tick “Different widths front and rear”: each wheel is calculated with its own width and its own load. A wider tire needs less pressure for the same tire drop.
What is the maximum pressure on a hookless rim?
72.5 psi (5 bar), per the ETRTO standard. The tool warns you as soon as the recommended pressure goes above it. Also respect the maximum pressures printed on your tire and your rim.
How is the pressure calculated?
We start from Frank Berto's rule: a well-inflated tire drops about 15% of its width under load. The surface changes that target drop, from 13% on a track to 19% on category 4 gravel; tire type and speed then adjust it using our simulation of the tire on the road.