Spoke Length Calculator

Classic and straight-pull hubs — Damon Rinard formula

Version

Lite Spoke lengths only, left and right Pro Tension targets, bracing angles, spoke catalog and stretch

Hub type

Classic (J-bend) Straight-pull

Rim

ERD, mm

Offset spoke bed (OSB), mm

0 for a symmetric rim

Hub

Left flange Ø, mm

Right flange Ø, mm

Left flange to center, mm

Right flange to center, mm

Spoke hole Ø, mm

Lacing

Number of spokes

Crosses

Spoke lengths

Left side (NDS)

0mm

Rounded: 0 mm

Right side (DS)

0mm

Rounded: 0 mm

* Verify lengths on a sample wheel before ordering a full set.

❓ How it works

Computes spoke length for classic J-bend (Damon Rinard) and straight-pull (chord + spoke offset). Shows bracing angles, tension ratio, target tensions and stretch estimate from a Sapim / DT / Alpina catalog.

📐 Formulas

Classic

L = √[(D/2·sin θ)² + (ERD/2 − D/2·cos θ)² + W²] − S/2

Straight-pull

L = √[...] + spoke offset (no hole Ø)

Tension

T_L / T_R = (W_L/L_L) / (W_R/L_R); tighter side = rim max

Stretch

ΔL ≈ F·L / (A·E), E = 210 GPa steel

📏 ERD and spoke offset

ERD = A + 2B (two opposite nipples plus two nipple lengths).

Spoke offset (straight-pull) is flange mid-line to head seat; 1:1 effect on length. Usually 0 for radial.

✅ Tips

All sizes in mm; use a dot as decimal separator.
Straight-pull cross count is fixed by hub geometry — do not invent it.
Target tension is a guide; match your tensiometer chart for the spoke model.
Stretch is informational and not added to order length (same as SpokeCalc).