Quick Tips: Checking Dirt Bike Sag
So many quick motorcycle maintenance jobs are incredibly simple, yet so beneficial to a machine’s performance. Measuring dirt bike sag is one of them.
Sag is the distance the suspension compresses (or sags) from its fully extended state when a rider is up on the bike. Correctly setting the sag on a dirt bike or dual sport is one of the most important adjustments you can make to improve your bike’s handling, and it can be done with a simple measurement tool.
Static sag (aka race sag or rider sag) is the amount of suspension compression from the weight of the motorcycle plus the rider. Free sag is the amount of suspension compression from the weight of the motorcycle alone without a mounted rider.
If the static sag is too tall, the rear shock won’t compress as much with the rider’s weight on it. This transfers weight to the front of the bike and reduces the weight at the rear. It also aids cornering, but is less stable along straightaways.
When the static sag is too low, the rear shock compresses too much with the rider’s weight on it, which transfers weight to the rear of the bike and reduces the weight at the front. It also aids tracking and stability in a straight line, but reduces front-end traction and cornering.
Tips For Checking Dirt Bike Sag
To check your dirt bike’s sag, use a tape measure or (preferably) a sag scale tool to measure the distance between a reference point on the rear fender and the rear axle. Mark the reference point on the rear fender so you’ll always measure from that exact same point.
Measure the sag only when the rear shock is cool and not hot from riding. Make sure the bike has a full tank of gas and is at its maximum weight. Have the rider wear his or her normal riding gear so that the weight matches their typical riding weight.
NOTE: Rider pictured is only a stand-in. When measuring sag, make sure the rider is wearing their full riding gear.
Next, ask the rider to stand on the footpegs to give a more consistent sag measurement than sitting on the seat. Finally, have the rider bounce up and down a couple of times to free up any stiction and allow the suspension to find its natural position.
Ready to measure the sag on your dirt bike? Watch the video above to see how to measure sag using a Motion Pro Sag Scale II tool.