05/02/2026
๐๐ก๐ ๐ซ๐๐๐จ๐ฎ๐ง๐ ๐ฌ๐ฉ๐ซ๐ข๐ง๐ ๐จ๐ซ ๐๐๐ ๐ข๐ง ๐ ๐ฌ๐ก๐จ๐๐ค ๐๐๐ฌ๐จ๐ซ๐๐๐ซ
In many racing shocks there is a ๐ซ๐๐๐จ๐ฎ๐ง๐ ๐ฌ๐ฉ๐ซ๐ข๐ง๐ mounted. The rebound spring is a short spring that works in extension of the shock, in opposing direction of the main spring. It is called a top out spring or TOS by many because it works against the topping out of the shock to full extension
The rebound spring is normally mounted around the shaft in the bottom of the shock absorber tube. It is designated by the rate x the stroke of the rebound spring for example 90N/mm x 12mm stroke is often labeled as โTOS 90x12โ
Many people call the reason for a rebound spring is to make the start of the stroke โsofterโ. However when we look at the graphs it shows the opposite, the wheel rate gets higher.
The rate of a spring can be seen in the force graph as the slope of the curve or (delta Force / delta Stroke). When we look in the graph we see the rebound spring makes the graph more steep.
In te rebound spring aera the total spring rate is the rate of the main spring + the rate of the rebound spring.
By having a more steep graph the start force can be lower, and this is the real benefit of the rebound spring. Every time the force of the shock comes below the preload force, without the rebound spring the contact with the road would be lost. When the contact with the tire would come back without the rebound spring, there is an impulse caused by the jump in force.
By using a rebound spring there is less of an impact and the wheel keeps on moving at lower wheel force, to be able to absorber all small movements of the rear tire.
Points of attention during setup of the rebound spring are
1) The unsprung mass (Swingarm, wheel and tire weight) is just hanging on the shock and the shock Is very close to full extension
2) Use the rebound spring with the lowest rate, a higher rate make the bike more nervous
3) Be aware of which point in the stroke the rebound spring comes in to action. You donโt want to move over this point to many times in critical areas like corner exit. It will make the bike nervous.
4) A very important thing is that the rebound spring has great effect on the feeling during entry. In fact it happens often that changing the rebound spring makes a rider feel that you made a change to the front of the bike!
Common rates and length of rebound spring of SBK shocks are rate 100, 125, 150 , 188 N/mm with a stroke of 8 or 12mm. By the use of hashtag geometry software you can analyze the effect in
numbers and graphs.
๐๐ง๐จ๐ฐ ๐ฐ๐ก๐๐ญ ๐ฒ๐จ๐ฎ ๐๐ซ๐ ๐๐จ๐ข๐ง๐ ๐ฐ๐ก๐๐ง ๐ฒ๐จ๐ฎ ๐๐ก๐๐ง๐ ๐ ๐ฒ๐จ๐ฎ๐ซ ๐๐ข๐ค๐๐ฌ ๐ฌ๐๐ญ๐ฎ๐ฉ!
