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Tiller calculator

Tiller is the balance between your two limbs: the top limb gap minus the bottom limb gap, measured with a bow square. The right number depends on how you hold the string. Enter your two readings and your hook to see your tiller, what it should be, and which limb bolt to turn if it’s off.

How to use it: String the bow, measure each limb gap with a bow square at a right angle to the string, set both sliders and pick your hook.

// The calculator

How you hold the string

7 1/4″
7 1/16″

With the bow strung, hold a bow square at a right angle to the string and measure to each limb’s belly right where it leaves the riser. Same spot every time.

Your tiller

+3/16″

Right for split finger

In millimetres+4.8 mm
Usual for split fingertop 1/8–1/4″ (3–6 mm) more

Nothing to fix: write the number down next to your brace height and go shoot.

7 1/4″ − 7 1/16″ = +3/16″

Tiller by hook (top gap minus bottom gap)

Split fingertop 1/8–1/4″ (3–6 mm) more
Three undereven, or the bottom up to 1/8″ more
String walkingbottom 1/8″ or more, more than the top

One-piece bow? Its tiller was set when it was built: a reading that changes points to a limb problem, so take it to a shop rather than turning anything.

// The math

How it’s calculated

Tiller = top limb gap − bottom limb gap. Each gap is measured with a bow square at a right angle to the string, from the string to the limb’s belly right where it leaves the riser (Lancaster Archery; Improve Your Archery).

What it should be depends on your hook (Olympian Jake Kaminski; Bow International; Glasgow Archers): split finger, the top 1/8–1/4″ (3–6 mm) more than the bottom; three under, about even or the bottom up to 1/8″ more; string walking, the bottom 1/8″ or more, more than the top. Tighten a limb bolt and that limb’s gap shrinks; loosen it and the gap grows. A quarter turn at a time.

A worked example

Top gap 7 1/4″, bottom gap 7 1/16″: 7 1/4 − 7 1/16 = +3/16″ (4.8 mm). For split finger that’s inside 1/8–1/4″: nothing to fix. Shooting three under, it’s set for split finger, so a quarter turn tighter on the top bolt starts evening it out.

The full explanation: Tiller in the glossary.

// FAQ

Questions about tiller

Quick answers about measuring tiller and changing it.

What should my recurve’s tiller be?

For split finger, the top limb about 1/8–1/4 inch (3–6 mm) farther from the string than the bottom. Three under runs about even; string walkers run the bottom farther.

Which way do I turn the limb bolt?

Tighten a bolt (clockwise) to make that limb stronger and shrink its gap; loosen it to grow the gap. A quarter turn at a time, and never past the turns your riser’s manual allows.

Can I change tiller on a one-piece bow?

No. The bowyer sets it when the bow is built, so a reading that changes means a limb needs a shop’s eye.

Jedain Aaron

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