Confused?

There are so many suspension adjustments on modern sports bikes that it is difficult to know where to start. Shock absorber spring ratings will have an affect on how well you can setup your bike to suit your size. Spring ratings are of course designed to suit the average sized rider and may need to be replaced if found to be unsuitable for you. Probably, the easiest place to start with is with your preload setting.

Preload Setting

Inadequate preload will result in wallowing, under brakes. Excessive preload will result in a rigid feeling from the rear, slow steering and a tendancy to stand up. Start with the rear because it has a greater influence on the front than visa versa.

'Free Height' Measurement

Place the bike on it's center stand or race stand. Lift the rear of the bike so that the rear shock is fully extended. Using a tape measure, measure the distance from the rear axle to a fixed point on the rear of the bike. Write this measurement down and title it 'Free Height'.

'Rider Sag' Measurement

Remove the bike from the stand and sit on the bike in the normal riding position (with all your riding gear on). 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'.

Ride Height Sag Calculation

Subtract the Rider Sag from the Free Height to determine the Rear Ride Height Sag. Ideally it will be 30-35mm (1.18-1.38") for touring and
25-30mm for (1-1.18") for sports bikes. To adjust, loosen off the lock nut on the shock were the spring sits and then wind the other nut up or down, constantly checking the measurements till you get it right.

Static Sag Calculation

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'.

Spring Rating Analysis

For a tourer you want 6-12mm and for a sports bike your want between 3-7mm. If you have less static sag than you should, then you have wound up too much preload on the spring to achieve the desired amount of rider sag & the spring is therefore too soft. If you have an excess of static sag then obviously you have too little preload indicating the spring is too strong 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.

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