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I've had to learn a bit about this subject in the last three years since I got into racing and I've been fortunate to have a couple of old hands at the game mentor me through it.
Previous to this I viewed suspension set up as a bit of a dark science, mainly because I didn't understand it.
I'm not saying I know it all now though - far from it. Just the other day I got a good tip off member @Engine-R about only doing your suspension adjustments when the suspension oil has been warmed up. Makes sense as this is the state the suspension will be in when your riding.
So I'd like to pass on a couple of things I've learned regarding the basics of setting up a race bike with adjustable suspension and also some of the mistakes I made.
Lets start off with the first assumption/mistake I made: Hard is good, soft is for road bikes. These days I'm running double the amount of static sag I was when I first started out and (on my SV) I have changed both front and rear springs for softer ones. Result: My lap times have improved and I now have better front end feel.
That rigid feel may be good for lessening pitching, nose dive under braking and wallowing but lets face it, how many tracks that we ride on are billiard table smooth? When your cranked right over and you hit an imperfection in the track if your suspension cant absorb some of that then your going to bounce of it and lose tyre contact knocking you off line and unsettling the bike, which in turn will unsettle you!
You also dont have that same feel of just how much your pushing the front end when its set up stiff and remote like.
So much of getting the correct set up is about spring rate. You must be prepared to change your springs to suit your body weight. After setting my spring preload to get the correct amount of static (bike) sag my rider sag figure was still too little because I'm a light weight. I tried to race it like this rather than invest in springs of the proper rate (and also because I thought hard = good) but ultimately I had to change my springs. Same goes if your a heavy weight. Screwing up your preload adjusters until you see better sag figures and turning your compression and rebound damping up is only going to mask the underlying issue that your spring rate is wrong for your body weight.
Setting your sags: First time I ever went to do this I couldnt work out why there was only about 1 mm difference between my unloaded figure and my static (bike weight only) figure no matter how much I adjusted the preload adjuster. Reason: I was using the paddock stand to unload the rear shock and of course this does not do that. Sure, the rear wheel comes off the ground but the suspension is still not unloaded because I wasn't holding the bike up by the foot pegs. Seems obvious now huh.
Static sag is the difference in measurement between that fully unloaded state I was struggling to find (topped out) and then measured again with the weight of the bike on the suspension.
Rider sag is taken using that same first unloaded measurement as a baseline and then re-measuring with the rider sitting on the bike and calculating the difference.
Front suspension is easier to measure because you just measure the amount of chrome showing on the stanchions. Make sure though that your using a stand that lifts underneath the steering stem to fully unload the suspension.
On the rear I like to stick a piece of pointed sticky tape directly above the rear axle nut on the tail section. Then I just rest the tape measure on top of the axle nut and measure up to the piece of tape. Its easier if you have someone to hold onto your bike for you.
Easiest way to get your rear end fully unloaded for measuring and working on the suspension is to lift it up on the paddock stand then slip two of those cheap automotive axle stands under each of the foot pegs (only works if you have solidly mounted foot pegs like on rear sets) now let the paddock stand down and you are good to go.
I'm almost reluctant to suggest sag figures as there are lots of personal opinions on this but, as a guide only:
Static: front 20 - 25mm, rear 5 - 10mm (I use 10, helps keep rear wheel on ground under heavy front braking)
With rider: (wearing all gear inc helmet) front 35 - 40mm, rear 25 - 30mm
Set your static sag up first using your preload adjusters then adjust your rider sag by changing your springs if need be.
As you can see the front requires considerable more sag than the rear end to be effective.
When measuring rider sag I get someone to do the measurements while I lean my elbow ever so slightly on an adjacent wall to hold the bike up. A third person is even better for doing this job though.
Something else that I'd like to mention is front fork friction.
After fitting the front axle you need to leave the pinch bolt loose until you have tightened the axle nut or screwed the axle fully into the fork leg depending on your set up. Then drop the front wheel off the bike stand and bounce on the front end a couple of times. This aligns the forks properly and now you can tighten the axle pinch bolt. Your forks will slide best in this position with least friction.
I think I will save damping for another night. To be continued
Previous to this I viewed suspension set up as a bit of a dark science, mainly because I didn't understand it.
I'm not saying I know it all now though - far from it. Just the other day I got a good tip off member @Engine-R about only doing your suspension adjustments when the suspension oil has been warmed up. Makes sense as this is the state the suspension will be in when your riding.
So I'd like to pass on a couple of things I've learned regarding the basics of setting up a race bike with adjustable suspension and also some of the mistakes I made.
Lets start off with the first assumption/mistake I made: Hard is good, soft is for road bikes. These days I'm running double the amount of static sag I was when I first started out and (on my SV) I have changed both front and rear springs for softer ones. Result: My lap times have improved and I now have better front end feel.
That rigid feel may be good for lessening pitching, nose dive under braking and wallowing but lets face it, how many tracks that we ride on are billiard table smooth? When your cranked right over and you hit an imperfection in the track if your suspension cant absorb some of that then your going to bounce of it and lose tyre contact knocking you off line and unsettling the bike, which in turn will unsettle you!
You also dont have that same feel of just how much your pushing the front end when its set up stiff and remote like.
So much of getting the correct set up is about spring rate. You must be prepared to change your springs to suit your body weight. After setting my spring preload to get the correct amount of static (bike) sag my rider sag figure was still too little because I'm a light weight. I tried to race it like this rather than invest in springs of the proper rate (and also because I thought hard = good) but ultimately I had to change my springs. Same goes if your a heavy weight. Screwing up your preload adjusters until you see better sag figures and turning your compression and rebound damping up is only going to mask the underlying issue that your spring rate is wrong for your body weight.
Setting your sags: First time I ever went to do this I couldnt work out why there was only about 1 mm difference between my unloaded figure and my static (bike weight only) figure no matter how much I adjusted the preload adjuster. Reason: I was using the paddock stand to unload the rear shock and of course this does not do that. Sure, the rear wheel comes off the ground but the suspension is still not unloaded because I wasn't holding the bike up by the foot pegs. Seems obvious now huh.
Static sag is the difference in measurement between that fully unloaded state I was struggling to find (topped out) and then measured again with the weight of the bike on the suspension.
Rider sag is taken using that same first unloaded measurement as a baseline and then re-measuring with the rider sitting on the bike and calculating the difference.
Front suspension is easier to measure because you just measure the amount of chrome showing on the stanchions. Make sure though that your using a stand that lifts underneath the steering stem to fully unload the suspension.
On the rear I like to stick a piece of pointed sticky tape directly above the rear axle nut on the tail section. Then I just rest the tape measure on top of the axle nut and measure up to the piece of tape. Its easier if you have someone to hold onto your bike for you.
Easiest way to get your rear end fully unloaded for measuring and working on the suspension is to lift it up on the paddock stand then slip two of those cheap automotive axle stands under each of the foot pegs (only works if you have solidly mounted foot pegs like on rear sets) now let the paddock stand down and you are good to go.
I'm almost reluctant to suggest sag figures as there are lots of personal opinions on this but, as a guide only:
Static: front 20 - 25mm, rear 5 - 10mm (I use 10, helps keep rear wheel on ground under heavy front braking)
With rider: (wearing all gear inc helmet) front 35 - 40mm, rear 25 - 30mm
Set your static sag up first using your preload adjusters then adjust your rider sag by changing your springs if need be.
As you can see the front requires considerable more sag than the rear end to be effective.
When measuring rider sag I get someone to do the measurements while I lean my elbow ever so slightly on an adjacent wall to hold the bike up. A third person is even better for doing this job though.
Something else that I'd like to mention is front fork friction.
After fitting the front axle you need to leave the pinch bolt loose until you have tightened the axle nut or screwed the axle fully into the fork leg depending on your set up. Then drop the front wheel off the bike stand and bounce on the front end a couple of times. This aligns the forks properly and now you can tighten the axle pinch bolt. Your forks will slide best in this position with least friction.
I think I will save damping for another night. To be continued