fork oil - level & wt

[Blue9R]

I have a Honda F2 track bike. I've got to have the front pre-load setting almost maxed out to keep the front end from diving. I'm going to change the fork oil. The manual recommends Honda SS-8 fluid. I believe this is a 10 wt fork oil.
Should I stay with the 10 wt oil and add a little more volumn? If so, how much extra should I put in? Or should I use the recommended amount and go to a heavier wt oil.
I want to try different oil before messing with the springs.

Thanks for your help.

[GSXR RACER MIKE]

Since I don't know those forks I am going to shy away from a specific answer, but I do have a couple other questions. Does that fork have compression and rebound adjusters on it? If so I wonder if you need to slow down your compression valving a little bit (don't go crazy on this if you do it though - only like a 1/4 to 1/2 turn in to start with because too much resistance will cause other problems in handling). The other thing I think of is weight transfer, are you transfering alot of your upper body weight into the handlebars under braking? You should be able to hold the grips loosely when under HARD braking by scooting back in the seat a little and gripping the gas tank with your legs to transfer your bodyweight into the bike at a lower point that is further back on the bike. There are pads you can buy that adhere to the sides of the tank for extra grip made just for this reason, though there are numerous ones out there the only one that pops into my head currently is STOMP GRIP. If you buy some pads of any brand I would suggest the rubber ones (often times clear in color), these will provide grip without hurting your leathers (the sand paper type pads will abraid your leathers over time).

Just a couple alternate ideas for you.

[Philbie]

What Mike said and I'll add this. Preload needs to be used in conjunction with the correct spring rate for your weight and riding type (track in your case). Along with the internal preload spacers the external adjuster will move your sag #'s up and down but within the "correct range" meaning that your free sag and total sag difference stays relatively constant even though the #'s themselves change.

I don't know the Honda forks either but going with a heavier oil will increase damping.

Increasing oil height will help prevent bottoming but also make the progressiveness of the "air spring" more noticable.

Honestly, I'd start with the correct springs. If there are damping problems (especially not enough rebound damping now) then a heavier oil would most likely help.

What is your weight and the current spring rates?

[96SNAKE/03RR]

I agree with these guys. I will add that being maxed out on preload is never good. It really makes for a crappy handling bike. Using Preload to compensate for brake dive isn't a good idea either. Use it to set your sag and custom tailor pre-load a little by feel/geometry desires if you choose.

I would get the correct springs and set oil level to stock height. Then test your compression damping and rebound settings during your maximum braking point(before turn 1) with these new springs. Just don't overdo it with these settings for braking as it will also change the bike's handling everywhere else. That's where good oil level/air gap testing will pay off. I prefer strong springs, less preload just as a reference.

Good luck.

[Blue9R]

The bike still has the stock springs in it. My wt is 210 + gear. I definitely need to improve my body positioning. I know that I'm relying on my arms too much.

Thanks

[Philbie]

To give you some idea how far off the spring rates are I did a little reseach for ya.

91-93 CBR600f2
Stock fork rate is .648kg/mm
Stock shock rate is 13.3kg/mm

94 CBR600f2
Stock fork rate is .72kg/mm
Stock shock rate is 13.8kg/mm

Recommended for your 210lb ass is:
Fork rate .957 (.95's)kg/mm
Shock rate 16.0kg/mm

To give you some idea how far off you are, you'd have to weigh 52lbs to make the stock spring in the 94 work according to the chart. So, you can either go on a diet of water and crumbs for about a year or put the more correct springs in it.

[Fargin_Bastige]

I would consult a suspension expert first. There are several differing views of spring rate and oil level from different people.

I used to run .95 springs on my bike when I was your weight. I found it to be too stiff and actually hindered my progress. When I softened the springs and worked with oil weight and damping adjustments, it resulted in a much better handling bike.

My suggestion is call GP suspension, Traxxion Dynamics.

I personally prefer GP suspension. 4&6 racing uses them (Safety First racing).