Shimming fork springs

[FinalImpact]

You need to aim for 10-15mm free sag with a rider sag of around 35mm. 25mm is track stuff... and still.

Free sag too little = spring too soft
Free sag too much = spring too hard

If you want to improve the dive under braking, raise the oil level in thr fork. I will asume that you bottom out the front end... add oil until you're just shy of hitting the bump stop. Figure it out when the spring & oil is out. Using a tyrap has a travel gauge work great.

To give you an idea on my FZ09. I use 0.90kg/mm fork spring. 42mm rider sag with no preload (adjustable om the 09). Free sag is 22mm. Oil level is 130mm instead of 148mm.

That's good for the track by the way... and still comfy on the road.

Rear sag is 35mm.

Off the top; how much does the 09 weigh and how much travel does it have front and rear? Did you swap the fork springs (implied above)? I ask as it also has larger tubes with more volume.

The 6's are in the 450 lb w/ ~5" of travel front and rear.

 

[Marthy]

Can't remember the fork travel on top of my head but it has more than a R1.

Oil level thing is fine tuning. First you need to make sure you have the right free sag/rider sag with the proper springs. You won't compensate a wrong spring with more oil. Oil level tune the amount of spring (if you want to call it this way) that you exponentially add the the over all spring rate of the bike. The "air spring" is progressive... in other words. Smaller the initial volume, higher rate it will increase as the fork compress.

So basically once you have the proper front & rear spring rate for your weight, use the fork oil weight that suite your bike/riding style the best. Then with some hard braking (use a tryrap on the fork) add oil until it doesn't bottom out on hard braking.

I didn't make this up... it's all out there. Just need to dig for the information.

Here's a good graph to explain the way it work. Actually use this to eyeball how much to raise my oil level. 148mm is OEM, I went for 130mm and it work great for me. Sonic spring call for a 120mm on the 09. Do some test...