Flex Archery: Arrow Spine & Shaft Stiffness Explained

In flex archery, arrow flex — also called arrow spine or shaft stiffness — describes how much an arrow bends as it leaves the bow. When you release the string, the stored energy transfers into the shaft, causing it to flex forward. How much it bends, and how quickly it recovers, directly affects whether the arrow flies straight or veers off course.

How Arrow Flex Is Measured

Arrow flex is quantified as a spine value — a number such as 300, 400, 500, or 600. Manufacturers measure it by applying pressure to the center of a supported arrow shaft and recording the force required to deflect it a set distance. A lower spine value means a stiffer shaft; a higher value means a more flexible one. The key variables that determine appropriate stiffness are the arrow's material, length, and diameter.

Why Flex Archery Matters for Accuracy

Choosing the wrong spine value is one of the most common causes of inconsistent groups. An arrow that is too stiff or too flexible for your setup will not recover properly after the shot, sending it off its intended path. Getting flex archery right is therefore a foundational tuning step, not an afterthought.

Key Factors When Choosing Arrow Flex

• Draw weight and draw length: Higher draw weights and shorter draw lengths call for stiffer arrows. Lower draw weights with longer draws require more flexible shafts. The force the bow applies to the arrow must match the shaft's resistance.
• Shooting style: Recurve and longbow archers typically need a higher spine value because those bows apply more direct force to the shaft. Compound archers using a release aid generally shoot a stiffer, lower-spine arrow because the release is cleaner and imparts less lateral force.
• Arrow length and weight: Longer, heavier arrows need a higher spine value to flex correctly; shorter, lighter arrows perform better with a lower spine value.
• Arrow material: Carbon, aluminum, and wood shafts each have distinct flex characteristics and spine value ranges. Match the material to your shooting goals — whether target archery or bowhunting.

Using Manufacturer Charts as a Starting Point

Most arrow manufacturers publish spine selection charts organized by bow type and draw weight. These are a reliable starting point for flex archery tuning, but treat them as guidelines. Real-world variables — point weight, nocking point height, and rest type — all influence how an arrow behaves in flight. Test and adjust until your arrow flight is clean and your groups are consistent.

For a deeper look at how spine values are defined and charted, see our full entry on arrow spine and how it affects your setup.