Motorcycle suspension setup for a track day starts with sag: how far the suspension compresses under the bike's weight and then under yours. Set sag first, put the damping back to a known baseline, then make one small change at a time and write it down. Most riders get more from that discipline than from copying a forum's click settings.
This guide explains the terms, how to measure sag, what preload can and cannot fix, and where damping fits in. It's general background. Your bike's owner's or service manual, the suspension manufacturer's guidance and a qualified suspension technician should take priority over any figure here.
Before you touch an adjuster
Suspension adjustment can't compensate for worn parts. Evans Brasfield's Motorcycle.com damping guide recommends sorting old fork oil, a tired shock or worn tyres first, because they change how the bike behaves whatever the clickers say.
Check your tyre pressures too. They affect how the bike feels before suspension does, and track pressures follow different rules from road pressures. Our track-day tyre pressure guide covers cold and hot readings.
Finally, record where every adjuster is now. If you can't get back to where you started, every later change becomes guesswork.
Free sag vs rider sag: why the names get confusing
Sag guides often seem to contradict each other because they use the same words for different measurements.
| Term | What it usually means |
|---|---|
| Free sag | How far the suspension compresses under the bike's own weight. AMCN calls this "static sag". |
| Rider sag | How far it compresses with the rider aboard in kit. Motorcycle.com calls this "static sag"; Race Tech uses "static" or "race" sag. |
Race Tech's sag instructions define static or race sag as "the amount the bike compresses from fully extended, with the rider on board", and free sag as the bike alone. AMCN's rider-sag guide uses "static sag" for the bike alone and "rider sag" for the loaded measurement. Neither is wrong. Just check which one a source means before comparing numbers.
In this guide, free sag means the bike alone and rider sag means you on board.
How to measure sag
You'll need a metric tape measure or sag tool, a notebook and, ideally, two helpers. Motorcycle.com's sag guide describes the method below, and Race Tech's rear-shock instructions use the same formula:
- Choose fixed measuring points. At the rear, measure from the axle to a point directly above it on the bodywork or subframe. At the front, Motorcycle.com measures from the fork wiper to the bottom of the triple clamp on conventional forks, or to the top of the axle clamp on upside-down forks.
- Measure fully extended (L1). Lift the wheel off the ground so the suspension tops out. Race Tech lists measuring L1 with the bike on the ground as error number one. If you do, sag "will not change with changes in Preload".
- Measure loaded, pushed down (L2). With the rider in their normal riding position and kit, push the bike down a little and let it rise slowly, then measure.
- Measure loaded, lifted (L3). Lift the bike a little and let it settle back, then measure again.
- Average L2 and L3. Sag = L1 − (L2 + L3) ÷ 2. Repeat the process without the rider for free sag.
The gap between L2 and L3 is caused by friction, often called stiction. Averaging them gives a fairer reading. Race Tech says that if the difference at the rear is more than about 4–5 mm, the linkage needs attention.
What sag figures should you aim for?
This is where you need to be most careful. The right figure depends on the bike's suspension travel, its design and what the manufacturer recommends. Here is what the sources above suggest as starting points:
| Source | What it suggests |
|---|---|
| Motorcycle.com | Rider sag of 25–30 mm for track and 30–35 mm for road; free sag of 0–5 mm |
| AMCN | Rider sag of 25–40 mm or more, with a rule of thumb of 25 mm for track and 30 mm for road; bike-only sag (its "static sag") of 5–10 mm |
| Life at Lean | Rear rider sag of about 25–30 mm for track, while some newer bikes run 45–50 mm at the front; free sag of 5–10 mm |
| Race Tech | Gives no general figure; points riders to its setup sheet or product search for recommended spring rate, preload and sag |
Track figures tend to be lower than road figures, but the sources disagree on free sag and the front end. Dan Netting's Life at Lean sag guide is a good example: some modern bikes run far more front sag than a generic rule would suggest. Start with your manual's figure where it gives one, and treat these ranges as a check that you haven't made an obvious mistake.
Preload changes sag, not spring rate
Preload is the adjuster most riders reach for first. It changes where the spring sits in its travel, which changes ride height and sag. It doesn't make the spring stiffer.
- Too much sag: add preload. Too little: take preload off. AMCN suggests one full turn of a front preload adjuster usually changes sag by around 1 mm, but check your own bike.
- Free sag tells you about the spring. Motorcycle.com explains that once rider sag is set, too little free sag suggests the spring is too soft for you, and too much suggests it is too stiff.
- Running out of adjustment is a clue. Visordown's suspension guide with Niall Mackenzie warns against running the front preload fully wound in. If there's still too much sag with the preload already wound well in, you need stiffer springs, not more preload.
A spring change is a job for a suspension specialist. Ask them which rate suits your weight in kit and how you'll use the bike.
Damping basics: rebound and compression
Once sag is right, damping controls how quickly the suspension moves. Rebound damping controls how fast it extends again after compressing. Compression damping controls how it resists being compressed.
Motorcycle.com's damping guide is clear on the order: start "with the sag properly set. If you don't, you won't get a good baseline." It then suggests:
- Find the factory baseline. Count the clicks as you turn each adjuster gently all the way in (clockwise), then return it to the factory setting.
- Check rebound in the paddock. Push the front down and release. It should return to where it started "and not beyond", in roughly a second.
- Test compression in small steps. Ride at the baseline, then try "a couple of clicks firmer" and "a couple clicks softer", noting how each one feels.
- Check the balance. Push down on the tank: the front and rear should compress and rebound together.
Visordown's advice is to "make adjustments one step at a time." Change one adjuster, at one end, by one or two clicks, and ride a full session before you decide.
Is the bike using its travel?
A cable tie around the fork leg shows how much fork travel you used during a session. Slide it against the fork seal before you go out and see how far it has moved when you come in. Visordown suggests aiming to leave around 10 mm of travel unused. Use that as a rough check, not a precise measurement: one big braking zone or kerb can move the tie.
What your telemetry can tell you about suspension
A GPS logger or lap-timer app doesn't measure suspension movement. Speed, position and estimated lean angle can show where a change coincided with a different lap, but they cannot tell you the fork bottomed out or the shock packed down. To record suspension travel directly, you need suspension sensors and a logger that accepts them. Our RaceBox vs AiM Solo 2 comparison notes that the AiM Solo 2 DL takes suspension sensors, while the standard Solo 2 and the RaceBox Mini don't.
Even without sensors, data helps you judge a change honestly. Did your lap times, corner speeds or consistency change after the adjustment, or did the track get busier or the temperature rise? Compare clear laps from sessions before and after, using our beginner's telemetry guide if the traces are new to you.
Keep a setup log
Write down, for each session:
- Front and rear preload as a measurement in mm, such as exposed adjuster thread, rather than only a count of turns
- Front and rear compression and rebound, as clicks out from a stated reference
- Tyre pressures and tyre condition
- Track, date, weather and session number
- What you changed and what you felt
That record is how you learn your bike. ApexIngest lets you record preload, compression, rebound, tyre pressures and gearing for each session, and shows how they differ from your last session at the same track. Try a supported recording in the import demo to see what ApexIngest makes of your data.
If you're unsure about anything here, ask whether your track-day organiser has a suspension technician in the paddock. A short setup session with someone who can see your bike is often the best money you'll spend on the day.