Animated service guide
Dirt Bike Sag Check, Animated
Sag is how far the rear settles under the bike alone (static sag) and with you on it in gear (rider sag, also called race sag). It sets the bike’s ride height and balance. Three measurements and a bit of math tell you if the preload is right, and the static number tells you if the spring suits your weight.
The animated guide loads here. Every step is also written out below.
Looking for the full article? How To Set Dirt Bike Suspension: Sag, Clickers And Setup By Rider Weight covers this job in depth. This page is the animated, step-by-step version used in the MotoMind app.
Before You Start
Tools
- Lift stand
- Sag gauge or a metric tape measure
- A helper
- Hook wrench (spanner) for the preload ring
- Brass or plastic drift if your ring has no locknut tool
Parts And Supplies
- Your full riding gear
- Notepad or phone to write down A, B and C
Safety
- Have a helper hold the bike upright for every loaded measurement.
- Clean the threads before you turn the preload ring. Grit locks the ring and damages the threads.
- On KTM shocks the ring is set with the shock off the bike. The shock holds high-pressure nitrogen, so follow the manual’s removal steps.
Step By Step
Know the two numbers
Static sag is how far the rear settles under the bike’s own weight. Rider sag (race sag) is how far it settles with you on board in your gear. Both are measured from fully extended, with the rear wheel off the ground.
Measure A, wheel hanging
Put the bike on a stand so the rear wheel hangs and the shock is fully extended. Measure from the center of the rear axle straight up to a fixed mark on the rear fender. KTM puts a SAG mark there. Write it down as A.
- Lift stand
- Sag gauge
Shop tip. Use the same two points every time, and measure on the line the axle travels. Factory Connection says reading off the swingarm arc can throw you off by up to 15 mm.
Measure B, bike alone
Take the bike off the stand. Your helper holds it upright by the bars, no rider on it. Measure the same two points again. That is B. A minus B is your static sag.
- A helper
Static sag (bike alone) Bike Spec Source KTM / Husqvarna / GASGAS MX 35 mm KTM 250 SX-F 2024 owner’s manual, PDF p. 47; 250/300 SX/XC 2024, PDF p. 40 Your manual may not list static sag. Yamaha’s 2026 YZ-F manuals only give the rider figure. Factory Connection treats static sag as a check on the spring, not a setting.
Measure C, rider on
Sit on the bike in full gear, feet on the pegs, in your normal riding spot. Bounce a few times and let it settle. Your helper measures again. That is C. A minus C is your rider sag.
- Full riding gear
- A helper
Shop tip. Race Tech takes two loaded readings, one after pushing down about 15 mm and one after lifting about 15 mm, then averages them. If they differ by more than 4 or 5 mm, the linkage needs attention.
Compare with your spec
Most motocross bikes want rider sag near a third of the rear travel. KTM’s 105 mm on 300 mm of travel is about 35 percent. Use the number your manual gives for your model.
Rider sag (race sag) Bike Spec Source KTM 300 XC (2024) 100 mm KTM 250/300 SX/XC 2024 owner’s manual, PDF p. 40 KTM / Husqvarna / GASGAS MX 105 mm KTM 250 SX-F 2024 owner’s manual, PDF p. 48 (same on 250 SX, 450 SX-F) Yamaha YZ250F / YZ450F (2026) 90 to 100 mm Yamaha YZ250F 2026 owner’s service manual, PDF p. 400; YZ450F, PDF p. 402 (“sunken length” with rider) Honda’s 2025 CRF-R owner’s manuals print no sag number. Check the Honda service manual or Competition Handbook for your model, and use your own manual for any other bike.
Shop tip. Not sure what to aim for? The free sag calculator on motomind.app turns your A, B and C into static and rider sag and compares them with common targets.
Set preload for rider sag
Loosen the locknut, then turn the adjuster ring. Tighter adds preload and reduces sag. Looser adds sag. Go in small steps, retighten the locknut, and measure C again.
- Hook wrench
- Drift
Shock spring preload Bike Spec Source KTM / Husqvarna / GASGAS MX 8 mm KTM 250 SX-F 2024 owner’s manual, PDF p. 49 (shock removed, hook wrench; M5 ring screw 5 Nm) Yamaha YZ250F / YZ450F (2026) 8.0 mm (1.5 to 18) Yamaha YZ250F 2026 OSM, PDF p. 122-123; YZ450F, PDF p. 121-122 (standard 8.0 mm, range 1.5 to 18 mm, 1.5 mm per ring turn) Check your manual for the standard preload and the allowed range.
Careful. KTM sets preload with the shock removed, and the shock holds high-pressure nitrogen. Follow the manual’s removal steps or let a shop do it. Never force the ring past the range your manual lists.
Shop tip. On a 2026 Yamaha YZ-F, one turn of the ring changes the installed spring length by 1.5 mm.
Check static sag
With rider sag right, look at static sag again. If you needed lots of preload and static sag is now too small, the spring is too soft for you. If static sag is too big with little preload, the spring is too stiff.
Use the static sag (bike alone) from the table above.
Shop tip. Factory Connection treats static sag as a check, not a setting. If it lands in range once rider sag is set, your spring rate is probably right.
Change the spring if needed
If preload can’t get both numbers in range, fit the spring rate made for your weight in gear. Then set preload, measure static and rider sag again, and reset rebound damping to suit the new spring.
Shock spring rate Bike Spec Source KTM 250 SX-F (2024) 39 / 42 / 45 N/mm KTM 250 SX-F 2024 owner’s manual, PDF p. 50 (riders 65-75 / 75-85 / 85-95 kg in full gear) KTM 450 SX-F, 250/300 SX (2024) 42 / 45 / 48 N/mm KTM 450 SX-F 2024 OM, PDF p. 49; 250/300 SX/XC 2024 OM, PDF p. 42 (riders 65-75 / 75-85 / 85-95 kg in full gear) Yamaha YZ250F (2026) 54 N/mm Yamaha YZ250F 2026 owner’s service manual, PDF p. 401 (standard; 52 to 60 N/mm optional) Yamaha YZ450F (2026) 56 or 58 N/mm Yamaha YZ450F 2026 owner’s service manual, PDF p. 403 (standard rate depends on market version) Your manual or the shock builder lists spring rates by rider weight. The rate is usually stamped or color-coded on the spring.
Shop tip. Write down A, B, C and the ring position each time. Next time you only need to remeasure C to know if the spring has settled.
Sources
Log It And Know When It Is Due Next
MotoMind logs engine hours and every service job with notes, parts and cost, and shows each task as upcoming, due or overdue. Available to download on iOS.
