How to Set Rider Sag DOWNLOAD INSTRUCTIONS 1) Rider sag is how much the suspension settles from FULL EXTENSION with the rider sitting on the bike.

The only way to get accurate full extension measurements is with the WHEELS OFF THE GROUND while the initial measurements are taken. This can be done by putting the bike on the center stand. If the bike does not have a center stand, then the wheels can be levered up one wheel at a time against the side stand and the other wheel.

See Picture #1.

 2) It is important to set the rear wheel to correct rider sag first as it affects the front fork sag.

Take the fully extended measurement with the rear wheel off the ground. At the rear wheel this is measured from the rear axle straight up to a good reference point on the bodywork or sub-frame.

See Picture #2.

 3) In this case, we have put a Sharpie dot on a piece of painter’s tape stuck on the body workto use as a measuring reference point.

Note that the measurement with the suspension fully extended is 568mm.

See Picture #3.

 4) Now the rider sits on the bike in the riding position with their gear on.

The bike should be on level ground. Both feet should be down with the rider balancing as much weight as possible on the seat. The rider’s hands should be on the handlebars, but do not pull on the control levers. The rider needs to HOLD STILL and not bounce on the bike.

See Picture #4

 5) The person taking the measurement should LIGHTLY push down on the seat behind the rider and release so that the suspension is settled into the rider sag position.

Then a measurement is taken from the rear axle to the mark on the subframe/bodywork that was used in the original fully extended measurement.

See Picture #5.

6) The second measurement taken with the rider on the bike is 508mm. To get the rider sag, you subtract the measurement taken with the rider on the bike from the fully extended measurement. So: 568mm - 508mm = 60mm

7) This particular bike has 200mm of rear wheel travel. You are after 30% of wheel travel in rider sag. 200mm x .30 = 60mm. So, in this example, the spring preload on the rear shock is set for the correct rider sag. If the sag is not correct, you adjust the spring preload on the rear shock to get the correct rider sag. Add spring preload to decrease the rider sag, subtract preload to increase the rider sag.

 8) Now that the rider sag is set correctly on the rear suspension, we will set the rider sag at the front of the bike with the fork spring preload.

With the rider off of the bike, and the suspension fully extended with the FRONT WHEEL OFF THE GROUND, measure the length of the exposed chrome slider on this USD fork.

See Picture #6.

 9) In this case, using the top edge of the dust seal as a reference point, the fully extended measurement is 222mm.

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See Picture #7.

 10) Now the rider sits on the bike again in the same manner as when the rear suspension measurement was taken.

Grasp the fork leg, crash bar, or whatever works for this particular bike and move the front fork up and down a little to get it to settle to its natural sag position. Take the second measurement. See Picture #8. The measurement in this case is 162mm.

11) Again, you subtract the measurement taken with the rider on the bike from the fully extended measurement. So 222mm – 162mm = 60mm.

12) This particular bike also has 200mm of front wheel travel. You are again after 30% of wheel travel in rider sag. 200mm x .30 = 60mm. So, the spring preload on the front forks is set for the correct rider sag. If the sag is not correct, you adjust the spring preload on the front forks to get the correct rider sag. Add spring preload to decrease the rider sag, subtract preload to increase the rider sag. If your forks have external preload adjusters, then use them. If your fork does not have external preload adjusters, the fork will need to be opened up to change the amount of spring preload internally.

13) Note that this is just the process for measuring sag and is assuming that the spring rates were chosen correctly in the first place.

 14) The bike in this example has a USD fork and a chain drive double sided swing arm. There are alternate suspension systems on other bikes.

For a shaft drive rear suspension, measure from the rear through axle if it is a double sided swing arm. If it is a single sided shaft drive swing arm, measure from the center of the final drive.

See Picture #9.

 For a BMW Telelever fork,

measure from the top of the dust seal on the slider on the front assembly to the bottom of the upper fork cross brace.

See Picture #10.

 For a conventional fork,

measure from the top of the dust seal to the bottom of the lower triple clamp.

See Picture #11.

 DOWNLOAD INSTRUCTIONS JAF 10/30/2024