Sag & spring check
Three measurements, five minutes, and the single biggest improvement most bikes can get for free.
Sag & springs
Three measurements tell you whether your preload is right and whether the spring suits your weight.
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Measure from the rear axle centre to a fixed mark on the fender, and use the same mark all three times. Have someone hold the bike upright for L3 while you sit in your normal riding position.
This reads the direction your spring is off, not which spring to buy. That depends on your bike’s stock rate and how you ride — take these numbers to a suspension shop before ordering.
How to measure
L1 — get the rear wheel off the ground so the suspension is fully extended. Measure from the centre of the rear axle to a mark on the rear fender directly above it. Use the same mark for all three measurements.
L2 — bike on the ground, no rider. Push down on the seat and let it settle, then lift and let it settle, and take the middle of the two readings.
L3 — sit on the bike in full riding gear, feet on the pegs, in your normal riding position, with someone steadying the bike. Settle it the same way, then measure.
What the numbers mean
Race sag is how far the bike settles with you on it. It is set with preload, and it is the first thing to get right.
Free sag is how far it settles under its own weight. Once race sag is correct, free sag tells you whether the spring matches your weight: too little free sag points to a soft spring, too much points to a stiff one.
This gives you a direction, not a part number. Which spring to fit depends on your bike’s stock rate, your weight in gear and how you ride — take these readings to a suspension shop before buying.
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