DIY Suspension Setup

I have to confess that I now 3/5th's of stuff all when it comes to suspension however my limited knowledge has made me aware that suspension and riding skills are the number one factor when it comes to trail bike performance.
 
Think about the last time that you were passed by alittle 250 whilst you were pushing as hard as hell on your trick 400. A classic example of this is Shane Watts. Wattsy managed to beat all comers at the Aussie ISDE a few years back on a well set up 125cc 2 stroke.

In recent times I have been shown first hand the dramatic effects that suspension and the adjustments that can be made and what it can do to a bike.

During the Finke Desert race I had plenty of problems with the bike wanting to go into tank slappers at high speed. With nothing mor ethan adjustment of the rear spring preload and adjustment on the compression and rebound of the shock and forks it was almost cured. Although not completely fixed it certainly made me more confident in racing the bike.

In most cases the front springs are pretty rite as they don't carry the bulk of the weight, that is the responsibility of the rear spring. Unless you are a featherweight or a heavy weight the front springs should be o/k.

So where do you start? that is simple, firstly you have to make sure that the shock spring is capable of handling your weight.Most of the trail bikes that are produced are for riders that are around the 80to 85 kilo mark. If you weigh more than 90 kilos then it is more then likely that the rear shock spring will have to upgraded. Prior to doing any work youwill have to check or do the following:

• Ensure that all the suspension linkages are free, greased and in good serviceable condition
• Make sure that all levels are at their maximum, this includes the fuel tank.
• Completely back off the compression and rebound to the softest setting taking a note of how many clicks you moved them.
• Put all you riding gear on including boots.

Why you ask? Have you weighed all your gearlately?

It will turn a 80 kilo rider into a 90 kilorider with no problems.

You will also need the following tools and equipment.

• A pen and a writing pad.
• A tape measure
• A stand that will get the back wheel of the ground.
• A helper

1. Place the bike on a stand with the rear wheel raised from the ground. Using a tape measure, measure the distance from the rear axle to a fixed point on the rear guard. Make sure that you mark these points that you have measured from as you will keep coming back to these exact points to ensure consistency.   Write this measurement down and title it "Free Height"_____________________
2. Remove the bike from the stand and sit on the bike in the normal riding position. Get your helper to bounce the bike up and down then let the bike settle. It is usually a good idea to do this near a wall as you have to have your feet on the pegs balancing the bike so that your helper is free to take another measurement. With you balancing on the bike get your helper to measure from exactly the same points as in the Free Height measurement. Write this measurement down and title it "Rider Sag"________________________
3. Now it is time to go back to school. Subtract the Rider Sag from the Free Height to determine the Rear Ride Height Sag.	eg: Free Height = 609mm Rider Sag = 518mm Ride Height Sag = 91mm
4. Ideally the figure should be between 85mm and 100mm with 90mm plus or minus 5mm the target. If the figure is to low then then the spring will have to be tensioned and likewise if the figure is high then the tension of the spring will have to be backed off. To adjust, loosen off the lock nut on the shock were the spring sits and then wind the spring up or down according to the figures that you have constantly checking the measurements till you get it right.	Free Height = Rider Sag = Ride Height Sag =
5. Now that you have the Ride Height Sag set correctly you can now check to see if the correct spring is fitted to the bike to match your weight. With the back wheel on the ground and you off the bike bounce the bike up and down a few times and let it settle. In exactly the same places as before, measure the distance again, and title it as "Static Height" ____________________________ Now take the Free Height measurement again and subtract the Static Height to determine the "Static Sag"________________________________________	eg: Free Height = 609mm Static Height = 587mm Static Sag = 22mm
6. Now here is the key to whole thing. Ideally the Static Sag should be between 10 and 25 mm. If the figure is below 10 mm then the rear spring is to soft for your weight. Likewise if the Static Sag is greater then 25 mm then the spring is to hard for your weight. If you have to high or to low figures then take the figures to your bike shop or suspension shop and discuss it further with them as it is more than likely that you will need to replace the spring.	Free Height = Static Height = Static Sag =

 By Rod Bahn