biketools.cc
Tool 02

Tire Pressure Calculator

CategoryTires
Setup30 mm on 21 mm · tubeless

Defaults per discipline

40%

Share of system weight on the front

Front — consensus3.26 bar47 psi
Rear — consensus4.45 bar65 psi
System weight83.0 kg40/60 front/rear
30 mm labeled21 mm internalhooked bead seat
fig. 1 — cross section at labeled widths (§5)
five methods, bar (§1–§5)
MethodFrontRearNote
Berto 15% drop3.2647 psi4.8971 psiTraditional 15% drop guideline (Berto, 1988).
Impedance2.7039 psi4.0559 psiLower for rough surfaces (impedance research).
Heine / BQ2.2533 psi3.3849 psiWide-tire philosophy, lower across the board.
ENVE chart4.4565 psi4.4565 psiFrom ENVE 2026 chart: SES 2.3 / Foundation (21 mm rim), 27 mm tire.
Silca pro4.7068 psi4.8270 psiReverse-engineered Silca Pro formula.

Consensus is the median of the available methods. The spread between rows is real disagreement between published methods, not noise — pick the philosophy that matches your priorities (§1–§4).

Notes — methodology

  1. §1

    Berto 15% drop

    Pressure for a 15% tire drop under load, per wheel. The oldest published load-based guideline and the baseline the other formula methods scale from.
    Source: Frank Berto via Sheldon Brown
  2. §2

    Impedance

    Berto scaled down by surface roughness and a tubeless allowance. Past the breakpoint pressure, vibration costs more than casing flex saves.
    Source: Silca / Poertner impedance series
  3. §3

    Heine / Bicycle Quarterly

    The wide-tire philosophy: supple casings at lower pressure roll as fast and ride better. Berto scaled by a discipline factor, lower across the board.
    Source: Jan Heine, Bicycle Quarterly
  4. §4

    ENVE chart · Silca pro

    Two manufacturer references for cross-checking the formulas: ENVE's 2026 published chart (tubeless only) and a reverse-engineered Silca pro-model fit. Out-of-range inputs are stated, not extrapolated silently.
    Source: docs/methodology/tire-pressure.md
  5. §5

    Hookless ceiling

    Hookless rims carry a hard 72.5 psi / 5 bar maximum per ETRTO and manufacturer spec. Values that exceed it are capped and flagged red — consider a wider tire instead.
    Source: ETRTO standards manual