Advanced Arrow Spine Selector
ALR-based recommendation · Moderate cam · 1″ insert depth · Nearest standard spine
Physics-based selection — applicable to all manufacturers. Spine is determined by draw weight, arrow length, and point weight.
Method
Axial Load Ratio
Applied Force ÷ Buckling Force
Applied Force ÷ Buckling Force
ALR band →
< 1.2 Very stiff
1.2–1.3 Physics Optimum / Stiff
1.3–1.5 Competition ✓
1.5–1.8 High FOC / Forgiving
1.8–2.2 Underspined
2.2+ Dangerous
Cell: SPINE — ALR / max GPI for ≥11% FOC
1
Find your draw weight row — left column in pounds. Use your peak draw weight as set on the bow.
2
Follow across to your arrow length — carbon shaft only, nock groove to end of shaft. Does not include the protruding point.
3
Read the spine number. Green outline = Axial recommended band (ALR 1.2–1.5). Blue cells have the option to step to a weaker (higher number) spine. Small number is actual ALR. For custom setups: axialbowstrings.com/tools/spine-calculator.html
ALR formula: Applied force = draw weight × 0.67 (moderate cam) × √(point ÷ 100). Buckling force = 8,757,000 ÷ (spine × eff. length²). Effective length = shaft length − 1″ insert depth.
Each cell shows the nearest standard spine to ALR 1.35 for that combination. Color reflects the actual ALR that spine produces — variation is real.
Fit: Very Stiff / Stiff / Ideal / Forgiving / Weak / Avoid. For aggressive or mild cams, non-standard insert depths, or custom point weights, use the online calculator.
Free for pro shop display. Print, frame, and distribute without restriction. No permission required.
© 2026 Axial Bowstrings
© 2026 Axial Bowstrings
axialbowstrings.comFull calculator & ALR methodology online