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Sag Setup 101

The single most important setting on your bike — and the first thing we check on every build. Here's how to measure and set it right.

What sag is (and why it matters)

Sag is how far your suspension compresses under weight. It sets your bike's ride height and balance — get it wrong and no amount of clicker fiddling will save the handling. There are two numbers that matter:

  • Static sag (free sag): how much the bike settles under its own weight, no rider.
  • Rider sag (race sag): how much it settles with you on it, in full gear, in your normal riding stance.

Rider sag is set by shock spring preload. Static sag is the tell-tale that confirms your spring rate is right for your weight.

What you'll need

  • A tape measure (mm)
  • A bike stand or a helper to hold the bike upright
  • A second person to read the numbers
  • Your full riding gear (boots, helmet, pack if you ride with one)

How to measure rider sag

  1. L1 — fully extended: put the bike on a stand so the rear wheel hangs free. Measure from the rear axle straight up to a fixed point on the fender or side panel. Write it down.
  2. L2 — with you on it: off the stand, bike upright, you seated in your riding stance with all your gear. Bounce the rear and let it settle. Measure the same two points.
  3. Rider sag = L1 − L2.
💡 Bounce and settle twice — once compressing, once from full extension — and average. Suspension has stiction; the true number sits between.

Target numbers

Starting points for a full-size dirt bike (adjust to discipline and feel):

Setting Typical target
Rider sag — Motocross 100–105 mm
Rider sag — Off-road / GP 105–110 mm (a touch more for comfort/traction)
Static sag 30–40 mm

Set rider sag first with shock preload (turn the collar in to reduce sag, out to add it). Then check static sag.

The spring-rate check (the important part)

Once rider sag is in range, look at static sag:

  • Static sag too little (< ~30 mm) → your spring is too soft; you cranked in preload to hit rider sag and the bike now tops out harshly.
  • Static sag too much (> ~40 mm) → your spring is too stiff; you backed preload way out to hit rider sag.
  • Both in range → your spring rate is right for your weight. 👍
⚠ If you can't get both rider sag and static sag into range at the same time, no clicker will fix it — you need a different spring rate. That's exactly the kind of thing TBT sets from your weight before touching anything else.

Don't forget the fork

Fork sag matters too, but it's usually set by matching front ride height / fork height in the clamps and correct fork springs rather than a preload collar. If the front pushes in corners or the rear feels high, front-to-rear balance (sag front and rear together) is usually the culprit.

Want it done right — or done for you? Bring it to TBT and we'll dial it in.

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General guidance from TBT Racing. Every bike, spring rate, and rider is different — when in doubt, or for a fully dialed setup, have TBT do it. Work on suspension at your own risk; components are under pressure.