Using your motorcycle owner’s manual remove the existing spring.

Step 1

Once the spring is removed be sure to not lose any of the unattached parts, install the spring.

Step 2

Once the suspension component is put back together re-fit your suspension to the bike.
Setting up the static sag and rider sag

* Rider sag is the amount a bike sags with the rider in a seated position.
* Static sag is the amount that a bike sags under its own weight.

First, measure and set rider sag, and then measure static sag.

Rider sag is set at a predetermined amount, to allow the suspension to operate in the correct part of its stroke. Typically, rider sag is about one-third of suspension travel. Motocross bikes and offshoots of them like the WR400/426 typically use 100mm of rider sag. Bikes like XRs, TTRs and other trail bikes use 85mm, and bikes in between, such as DRZ, use 90-95mm. The KTM PDS system works best with 90mm. Road bikes do vary model to model, but 35-40mm is often used for sports bikes. Sag is adjusted by increasing or decreasing spring preload by turning the threaded preload collars on top of the shock spring. Increasing spring preload will give you more ride height/less sag, and vice versa. Rider sag and static sag are determined by making measurements of the bike when loaded and unloaded. It is vital that the measurement is made from the same two points in each stage of the process.

Step 4

Rider sag test

• Put the bike on a stand with the rear wheel off the ground. With a texta, make two marks, one on the rear fender, directly above the axle, and the other on the top of the axle nut. Measure the distance between the two marks. Our example is 650mm.
• Take the bike off the stand, and have the rider to sit on the bike in their normal riding position, with all their weight on the bike. Take another measurement between the same two points. Our example is 550mm
• The rider sag in our example is 100mm. If you're making this measurement on an MX bike you're spot-on.

Step 5

Static sag test

• Allow the bike to rest on the ground, without a rider. You will need to help it balance. Take another measurement from your two-texta marks. Push the seat down and then let it up by itself. Take a measurement. Pull the seat up and then let it go. Take another measurement. If there are any variations, use an average. If there is more than 5-7mm difference, you may have a problem with binding in the linkages. Our example is 610mm.
• Subtract this measurement from your first one (650mm, remember?). Static sag should be between 18mm and 32mm for dirt bikes and 5-15mm for road. (please see www.teknikracing.com for the road bike suspension tips in more detail) If it's less then 18mm, the shock spring is too soft for you. If it's more then 32mm, the spring is too hard. 25mm to 30mm is ideal. In our example, static sag is 40mm, so a softer spring needs to be fitted.

After all this, you might be wondering how important sag height is. A spring is just a spring right? Wrong!

* Soft springs need too much preload to prevent the bike riding low in the shock’s stroke, causing harshness, and making it kick on the entry to corners, especially in braking bumps.
* Hard springs won’t allow proper squat, making the rear-end uncompliant. Your bike will ride high in the rear, increasing headshake.
Many MX bikes are made with a higher steering head angle, which causes them to steer slower in the bush. For MX models, reduce static sag by 5mm to tighten the steering angle.