05-01-17, 11:30 AM
(This post was last modified: 05-01-17, 11:41 AM by tommyardin.)
[size=1em]After recently doing some suspension modding on my FZS600, I have been reading a lot about bike/suspension set up and there is one thing that is confusing me.[/size]
[size=1em]Nearly all stuff I have both read (On-Line) and watched (YouTube) say that it is important to set the static (Just weight of motorcycle) sag before doing anything else.[/size]
[size=1em]This procedure is: [/size]
[size=1em]Raise the front of the bike off the ground, to allow front forks to be fully extended. (Centre stand with a prop under the engine) measure from the top of the fork leg oil seal to the underside of the bottom yoke. Mine is exactly 150mm fully extended (Now there a coincidence)[/size]
[size=1em]Set the bike back on its wheels (Off the stand) and bounce the bike up and down a few times without using the front brake and allow the bike to settle under its own weight and remeasure the distance from the top of the fork leg oil seal to the underside of the bottom yoke again. Deduct this figure from you fully extended measurement and you have static sag. Mine is 126mm giving me 24mm of Static Sag on the front end.[/size]
[size=1em]The procedure for the rear of the bike is much the same by getting the weight off the back wheel (Just centre stand will do that ) but you will need to stick a parcel or paper label on the rear seat fairing vertically above the rear wheel axle, measure the fully extended measurement up from the underside of the axle (Sprocket side is easier as no exhaust can in the way) and put a pen mark on the label as a datum point (I used 450 mm)[/size]
[size=1em]Set the bike back on its wheels, bounce up and down on the back of the bike a few times just to settle the suspension and allow the bike to come to rest under its own weight, then measure the distance from the underside of the axle to your datum mark you put on the paper label earlier. Mine is 432mm from the original 450mm measurement giving me 16mm of static sag.[/size]
[size=1em]The next procedure is to set the Rider Sag, again this is taken from the full extended suspension measurements. My front forks full extended 150mm as above, my back shocker fully extended (Using datum mark 450mm), now the rider with all his riding gear on, leathers, boots, gloves and bucket sits on the bike bounces a few times, without touching the brakes and the measurements are taken again, this measurement is then deducted from the fully extended measurement and the remainder is your rider sag.[/size]
[size=1em]Ideal rider sag, now there seems to be a plethora of opinions on this and I think it could be to do riding style, or whether the bike is used for commuting or for track day events, or maybe just personal preferences. The figures I am going to aim for and that seems to be the most commonly occurring figures for a road bike (spirited riding style) is 40mm front rider sag and 30mm rear rider sag.[/size]
[size=1em]Now here is the rub, that which causes me confusion, why do we have to go through the static sag process at all? Because if the rider sag is not within the measurements we are looking for, we adjust our pre-load to get to those measurements, we have now undone all the static sag setup we went through. All the measurement for Static and Rider Sag are taken from the fully extended measurements.[/size]
[size=1em]A couple of mates are very useful when setting up these sag measurements to hold the bike upright without either applying up or down force when the measurements are taken, plus you will be sitting on the bike for rider sag measurements. [/size]
[size=1em]Nearly all stuff I have both read (On-Line) and watched (YouTube) say that it is important to set the static (Just weight of motorcycle) sag before doing anything else.[/size]
[size=1em]This procedure is: [/size]
[size=1em]Raise the front of the bike off the ground, to allow front forks to be fully extended. (Centre stand with a prop under the engine) measure from the top of the fork leg oil seal to the underside of the bottom yoke. Mine is exactly 150mm fully extended (Now there a coincidence)[/size]
[size=1em]Set the bike back on its wheels (Off the stand) and bounce the bike up and down a few times without using the front brake and allow the bike to settle under its own weight and remeasure the distance from the top of the fork leg oil seal to the underside of the bottom yoke again. Deduct this figure from you fully extended measurement and you have static sag. Mine is 126mm giving me 24mm of Static Sag on the front end.[/size]
[size=1em]The procedure for the rear of the bike is much the same by getting the weight off the back wheel (Just centre stand will do that ) but you will need to stick a parcel or paper label on the rear seat fairing vertically above the rear wheel axle, measure the fully extended measurement up from the underside of the axle (Sprocket side is easier as no exhaust can in the way) and put a pen mark on the label as a datum point (I used 450 mm)[/size]
[size=1em]Set the bike back on its wheels, bounce up and down on the back of the bike a few times just to settle the suspension and allow the bike to come to rest under its own weight, then measure the distance from the underside of the axle to your datum mark you put on the paper label earlier. Mine is 432mm from the original 450mm measurement giving me 16mm of static sag.[/size]
[size=1em]The next procedure is to set the Rider Sag, again this is taken from the full extended suspension measurements. My front forks full extended 150mm as above, my back shocker fully extended (Using datum mark 450mm), now the rider with all his riding gear on, leathers, boots, gloves and bucket sits on the bike bounces a few times, without touching the brakes and the measurements are taken again, this measurement is then deducted from the fully extended measurement and the remainder is your rider sag.[/size]
[size=1em]Ideal rider sag, now there seems to be a plethora of opinions on this and I think it could be to do riding style, or whether the bike is used for commuting or for track day events, or maybe just personal preferences. The figures I am going to aim for and that seems to be the most commonly occurring figures for a road bike (spirited riding style) is 40mm front rider sag and 30mm rear rider sag.[/size]
[size=1em]Now here is the rub, that which causes me confusion, why do we have to go through the static sag process at all? Because if the rider sag is not within the measurements we are looking for, we adjust our pre-load to get to those measurements, we have now undone all the static sag setup we went through. All the measurement for Static and Rider Sag are taken from the fully extended measurements.[/size]
[size=1em]A couple of mates are very useful when setting up these sag measurements to hold the bike upright without either applying up or down force when the measurements are taken, plus you will be sitting on the bike for rider sag measurements. [/size]