Spring vs Rebound Stock 08 Sprint ST

Ok first off a thanks to BruceC for allowing me to visit for awhile and take some readings and adjust some settings on the forks.

If anyone has ever pushed on the front end of a Truimph Sprint ST you will find that they are very soft in regards to the rate of the springs in the forks. Why the engineers did this who knows. Bruce and I took some measurements with the stock springs and without a rider just to see how soft they were.

With no rider and the preload adjusters all the way in to the last line we got 32mm sag (Remember this was with no rider) , After that measurement we backed the adjusters all the way out and got 36mm sag (No rider here either). As you can see without adding any more preload to the stock springs they are marginal at best. Normally without a rider (Free sag) you would want right about 20mm of sag.

We also had a little time to hook up some data acquisition and take a few readings. What you see in the graph is what happens after I performed the push test on the front forks and how they reacted in regards to rebound and if there was any signs of a pogo effect.

In this first image the preload adjusters were all the way in to the last visible line, As you can see with the adjusters turned all the way in and stock fork fluid in the forks we have the start of the pogo effect. So the rebound is too fast and you would either need to change the fluid to a heavier fluid or revalve the forks. When you change the fluid you would also affect the compression side of it.


In this image you will see the effects that backing the preload adjuster all the way out have, It brought the rebound under control as compared to the first image, It still shows a little sign of the pogo effect.


This image is after the Installation of some .95 Racetech Springs, Notice the pogo is back again? Yep she still needs a little work on valving or some heavier fluid in the forks.