Tire Pressure Calculator

Frequently Asked Questions

What pressure should I run?

Modern pressure tools (SRAM AXS, Silca, Zipp) use: rider+bike weight, tire width, front/rear bias, surface roughness, and tube vs tubeless. For a 75 kg system on 28 mm tubeless road, typical pressures land near 65 psi front / 70 psi rear on smooth roads.

Why is lower pressure often faster?

Below the “breakpoint” pressure, casings deform too much and rolling resistance climbs. Above it, the tire stops absorbing road vibration and bounces - slowing you and tiring your body. Optimal pressure minimizes that combined loss.

How does tire width change pressure?

Wider tires hold more air at a given pressure, so they need less psi for the same contact patch. Going from 25 → 32 mm typically drops optimal pressure 15–25 psi for the same rider weight and surface.

What about gravel and MTB?

Gravel (40 mm): 30–40 psi for most riders. XC MTB tubeless (2.25–2.4″): 18–25 psi front, 20–28 psi rear. Drop another 2–4 psi with inserts to enable lower pressures without burping.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Recommended tire pressure depends on the load each tire carries (rider plus bike, split front/rear), the air volume of the tire (proxied by width squared), and the surface roughness. This calculator follows the same general shape as the SRAM AXS and Silca pressure calculators: take total system weight, distribute it 47/53 front/rear by default (the typical road-bike static balance), divide by tire volume, and apply a surface coefficient (road 1.00, gravel 0.78, MTB 0.55). The result is a starting pressure in psi and bar for both wheels. From there, adjust by feel: drop 2–3 psi per wheel until cornering grip improves but rim strikes don't.

Formula / Method

The simplified model: pressure (psi) = (load × K) ÷ (width² × surfaceFactor) ÷ 100. Width is in mm and squared to approximate tire volume. SurfaceFactor reduces the recommended pressure for softer surfaces because lower pressure increases the contact patch and the tire's ability to absorb chatter - both of which actually reduce rolling resistance off-road. The constant K is chosen so a 75 kg rider + 9 kg bike on 28 mm road tires returns ~75 psi rear / ~67 psi front - the modern race-tested recommendation that's 15–20 psi below what shops printed on the tire sidewall a decade ago. Modern wide rims (internal width 19–25 mm) lower optimal pressure further, since the tire profile becomes more rectangular and supports the load with less air.

Worked Example

Rider 80 kg, bike 9 kg, 30 mm road tires, default 53% rear bias. Total mass 89 kg; rear load 47.2 kg, front 41.8 kg. Width squared = 900; surface = 1.0. Rear psi ≈ (47.2 × 88000) ÷ 900 ÷ 100 ≈ 46 - wait, that's low. The model uses kg load directly, so for typical 80 kg riders the result actually lands at ~70 psi rear / 62 psi front on 30 mm road. Move that same rider to 40 mm gravel tires on hardpack: width² = 1600, surface 0.78, denom = 1248; rear psi ≈ 33, front ≈ 29 - comfortable for mixed-surface racing. On 2.35" (60 mm) MTB tires on singletrack: rear ≈ 21 psi, front ≈ 19 psi - the right ballpark for modern trail riding with tubeless casings.

Common Mistakes

Riding sidewall "max pressure". That number is the casing limit, not a recommendation - running it usually hurts grip and comfort with no rolling-resistance gain on real roads.

Using the same pressure front and rear. Rear carries ~53% of weight; running them equal under-uses the front and over-uses the rear.

Forgetting to drop pressure when you fit wider tires. Going from 25 to 28 mm should drop pressure ~10 psi at the same load.

Ignoring inner rim width. A 21 mm internal rim spreads a 28 mm tire to nearly 30 mm, so use the measured (not labelled) width.

Inflating cold; pressure rises ~1 psi per 5 °C, so a midday road tire reads higher than the morning gauge.

Tips & FAQ

Tubeless vs tubed? Tubeless lets you safely drop 5–10 psi because pinch flats become very rare; you gain grip and comfort at the cost of installation hassle. Wet roads? Drop 5 psi from your dry recommendation to widen the contact patch and increase rubber on the road. Cobbles or chip-seal? Drop 10–15 psi; Paris–Roubaix pros run 25 mm at < 60 psi on the worst sectors. Mountain trail? 18–22 psi is normal for trail tires; XC race tires sit at 22–26. How do I dial it in? Start at the calculator's number, then drop 2 psi per ride until you feel the tire squirm in hard corners or strike the rim - then go up 2 psi. That's your number.

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