Motorcycle Suspension Setup Basics: Sag, Damping and Preload
Suspension setup is one of the highest-return adjustments you can make to a motorcycle — it costs nothing if the adjusters are already there, and the difference between badly set and correctly set suspension is enormous in both feel and performance. This guide explains the fundamentals clearly and practically.
Sag: The Starting Point for All Setup
Sag is the amount the suspension compresses under the weight of the rider. Setting correct sag is the first step in any suspension setup — it establishes the correct ride height and ensures the suspension can work in both directions from its neutral position.
How to Measure Sag
Rear sag measurement:
- Measure the distance from a fixed point on the rear subframe to the rear axle with the bike off its stand (supported upright by an assistant) — this is the fully extended measurement (L1)
- Sit on the bike in normal riding position. Have an assistant take the same measurement — this is the rider sag measurement (L2)
- Rider sag = L1 minus L2
Target sag figures:
- Sportsbike/supersport: 25–33mm rider sag
- Naked/streetfighter: 30–35mm rider sag
- Adventure/touring: 33–40mm rider sag
Preload: What It Does (and Doesn't Do)
Preload is widely misunderstood. Preload does NOT change the spring stiffness — it adjusts the initial compression of the spring, which changes the ride height and therefore the sag.
Increasing preload raises the bike (reduces sag). Decreasing preload lowers the bike (increases sag). That's all it does.
The common mistake is increasing preload to maximum to try to make the suspension "stiffer" for a heavy rider. This doesn't work — you can't compress the spring to the point of stiffness without running out of suspension travel. If the standard spring rate is too soft for your weight, you need a stiffer spring — adjusting preload will not solve the problem.
A useful guide: if you need more than 5–7 full turns of preload adjuster to achieve correct sag, the spring rate is wrong for your weight and a spring upgrade is the correct solution.
Compression Damping: Controlling Dive
Compression damping controls how quickly the suspension compresses under load — braking, hitting bumps, entering corners. More compression damping slows the compression movement; less allows it to compress more freely.
Too much compression damping: the suspension feels harsh, the bike bounces over bumps rather than absorbing them, and tyre contact is broken over rough surfaces.
Too little compression damping: the forks dive excessively under braking, the bike pitches forward dramatically, and handling stability is reduced.
Start at the manufacturer's recommended setting (typically mid-range) and adjust one or two clicks at a time, evaluating the change before adjusting further.
Rebound Damping: Controlling Return
Rebound damping controls how quickly the suspension returns after compression. It's the most common source of handling problems when incorrectly set.
Too much rebound damping: the suspension compresses over a bump but doesn't return quickly enough before the next one, progressively "packing down" over a series of bumps. The bike feels low and wallowy after a series of rough sections.
Too little rebound damping: the suspension returns too quickly, causing the wheel to "kick back" over bumps and creating an unstable, bouncy feel.
Rebound is typically adjusted separately for front and rear. Work on each independently — adjust front rebound, evaluate, then adjust rear rebound.
Road vs Track Settings
Road and track environments reward different suspension setups:
- Road: Slightly softer settings tolerate rough surfaces and provide better comfort without sacrificing too much precision. Prioritise compliance over outright rigidity.
- Track: Stiffer compression, faster rebound, and higher preload for the more consistent, smooth surface. Maximises feedback and precision at the expense of comfort.
If you use one bike for both, a road-biased setup is the better compromise — a slightly soft track setup is manageable; an overly stiff road setup is tiring and reduces safety.
When Adjustment Isn't Enough
If you've adjusted correctly and the suspension still doesn't feel right, the components may need replacement. Suspension fluid degrades over time (typically service every 15,000–20,000 miles), and springs lose rate. Browse our suspension range or read our suspension upgrades guide.