As much as your own machine’s manufacturer specifies — measured in the position they specify. The figure and the position are one instruction, not two: the same chain reads differently on a side stand, on a paddock stand and with a rider seated.
Why the position is part of the figure
The swingarm pivots. As it moves through its travel, the distance from the gearbox sprocket to the rear sprocket changes, and the chain is tightest at one point in that arc. A manufacturer specifies slack at a defined state of the suspension so that the chain is never taut at the tight point. Quote the number without the state and you have quoted nothing.
Where to measure it
At the point the manual specifies, usually mid-run between the sprockets, pushing the chain up and down and reading the total movement. Do it at several points around the chain by rolling the wheel: a chain with uneven wear will show more slack in one place than another, and the tightest point is the one to set.
What too tight does
A chain with no slack at the tight point of the suspension travel loads the gearbox output bearing and the wheel bearings every time the suspension compresses. It is the more damaging of the two errors, and it is the one people make when they set slack with the machine on a stand and never check it with weight on.
What too loose does
The chain slaps, wears its rollers and sprockets faster, and in the worst case can leave the sprocket. It is also the state a chain drifts into, because chains stretch with use — which is why this is a regular check rather than a one-off adjustment.
The uneven-slack signal
If the slack varies noticeably as the wheel is rolled, the chain has stretched unevenly and is near the end of its life. At that point adjustment stops being the answer, and the sprockets it has been running against are usually worn with it.
Questions riders send in about this
Can I use a figure from another machine?
No. Slack depends on swingarm geometry and varies widely, which is why it is published per machine and always with the position it was measured in.
How often should it be checked?
At the interval your manual gives, and additionally whenever the chain has been cleaned, after a long trip, or if the noise from the chain changes.
Last reviewed 18 September 2026