Tiller is the measurement from the string to the limb pocket — top and bottom independently. When both measurements are equal, the bow is in neutral tiller. When one limb bolt is backed out relative to the other, the tension on that limb is reduced, which shifts the effective pivot point of the bow and changes the nock travel path through the shot.
What tiller adjustment actually does
Backing out a limb bolt reduces the preload on that limb. With less preload, that limb contributes slightly less to the draw force curve through the shot. The result is a geometry shift: the cam on the lower-tension limb moves through its cycle at a marginally different rate, the string's departure angle changes slightly, and nock travel deviates from the manufacturer's intended path.
This is mechanically similar to what cam timing adjusts — both are manipulating the relative energy contribution of the two limb-and-cam systems through the shot cycle, and both express their effect as a change in vertical nock travel. Tiller is a coarser and less direct way to achieve something that timing does more precisely. It introduces the geometry change at the limb preload level rather than at the cable, which means the whole draw force curve shifts, not just the cam synchronization.
Where tiller has value: recurve
On a recurve, the archer draws with fingers and the bow has no cams. Tiller adjustment changes the balance of limb energy at the shot, which shifts the arrow's launch angle and can be used to fine-tune nocking point height without physically moving the nock. Because a recurve has no cam timing to set and no draw stop to reference, tiller gives the technician a geometry lever that would otherwise not exist. The indicative value is real.
On a compound, that lever already exists in the form of cam timing, draw stops, and the nocking point itself — all of which are more direct and more precise than tiller adjustment. The recurve use case does not carry over.
Do not use tiller to adjust the hold of a compound bow
Some compound archers adjust tiller to change how the bow feels at the back wall — to make the hold feel softer or stiffer on one side. This is the wrong tool for that problem. The feel of the back wall on a compound bow is a function of draw length, cam design, and wall hardness — not limb preload balance. Tiller adjustment to change the hold introduces a geometry imbalance that will express itself in nock travel, cam timing, and group consistency, without reliably solving the feel problem it was meant to address.
Axial's position: hold manufacture geometry
Axial recommends that compound bows remain in perfect manufacture geometry. Both limb bolts should be at the same position — and when possible, both should be maxed out. A fully-seated limb bolt puts the limb at its maximum preload and holds the limb pocket geometry at the position the bow was designed around. Backing out a limb bolt to achieve equal tiller on a bow that is not quite symmetrical is less correct than leaving both bolts fully seated.
If a bow shows unequal tiller with both bolts maxed, that is a manufacturing tolerance issue — not a tuning opportunity. Address it by checking limb seating and limb pocket geometry. Do not compensate with asymmetric bolt position.