You know the feeling — you throw a leg over your bike and either need a stepladder or feel like you’ve accidentally hopped onto a kid’s minibike.
Welcome to the wonderful world of preload and sag — two of the most misunderstood (and most critical) aspects of dirt bike suspension tuning.
Today, we’re starting with the basics:
How preload affects sag, and how sag affects everything else — seat height, handling, comfort, and how soon you might be cartwheeling off the trail if you get it wrong.
Preload: It’s Not Just for Show-Offs
Preload is how much tension is on your springs before you even sit on the bike.
Think of it like stretching a rubber band — the more you stretch it, the more energy it’s ready to unleash.
On most dirt bikes, preload is adjusted with a big threaded collar around the rear shock (and with spacers or internal settings in the fork).
Adding preload raises the bike’s resting height. Reducing preload lowers it.
👉 More preload = higher ride height, quicker steering, but a harsher feel.
👉 Less preload = lower ride height, slower steering, plus a cushier feel — until you bottom out and cry.
Sag: Where the Magic (or Misery) Happens
Sag is how much your bike settles down into its suspension under weight.
There are two flavors you need to measure:
- Static Sag (bike alone)
- Rider Sag (bike + fully geared-up rider)
Typical target ranges:
- Static Sag: 30–40mm
- Rider Sag: 95–110mm
If you’re way outside these numbers:
- Too little sag? Your spring is too stiff (or you skipped breakfast for a week).
- Too much sag? Your spring is too soft (or you ate all the tacos).
Quick Guide: How to Set Your Sag
- Lift the bike so both wheels are off the ground. Measure from the axle to a fixed point above (like a fender bolt or grab handle).
Write this down — it’s your Fully Extended Measurement. - Set the bike down and let it rest under its own weight (no rider). Measure again.
Subtract this number from the fully extended measurement = Static Sag. - Now, gear up like you’re ready to ride (helmet, boots, backpack — the whole nine yards).
- Sit neutrally on the bike (no bouncing, no feet down) and measure again.
Subtract this number from the fully extended measurement = Rider Sag. - Adjust preload to get your Rider Sag into the 95–110mm range.
(Bonus points if Static Sag also ends up between 30–40mm.)
Pro Tip:
If you can’t hit the right numbers even after cranking preload all the way up or down, your spring rate is wrong.
(It’s not you. It’s physics.)
Seat Height: Your New Best Frenemy
Chasing a “perfect” seat height?
Tuning preload and sag properly is step one — but lowering seat height too much through preload alone is a bad idea. You’ll destroy your handling.
Too much lowering =
- Wallowy cornering
- Headshake at speed
- Easy bottoming out
- Endless regrets
Real solutions for a lower bike:
- Lowering links
- Shaving seat foam
- Professional suspension lowering services
Don’t ruin your ride chasing that extra inch the wrong way.
Coming Up Next: Part 2 — Clickers, Compression, and Rebound Sorcery
In Part 2, we’ll dig into clicker tuning — what all those little knobs do, why random twisting is a bad idea, and how to set up your suspension like you almost know what you’re doing.
Stay tuned — and stay rubber-side down!
