[Mathieu9836]

Hi folks, i've been lookinf for a while a different solution to get a better front suspension. Here in the great north there is not much big suspension shops and i try to make things on my own. I came across a set of used ohlins that sold in 15 minutes... So i was thinking if getting a gold valve was worth the money or if the OE piston get the job done. I think i adjusted the suspension pretty much spot on, but there is still a little something missing. Roads are not the greatest where i live, so i need a plush yet stiff enough for high speed curves. I use 5W oil, added an additional 10mm oil in the forks for a test so i can get a smoother compression up top and its getting more firm at the end of the stroke, front end is 5mm lower, i will add a 5mm shim on the rear shock. Any idea other then that? Oh and if you guys have good read about suspension and geometry tuning, it would be much appreciated!

 

[JCW]

Traxxion dynamics make a very good AK-20 cartridge kit... but priced about the same as Ohlins nix30.
I believe I recall they will reshim/revalve your stock forks if you are on a budget to fit your needs, too. If you call them up they can maybe help point you in the right direction.

Trouble shipping forks back and forth to canada?

 

[alexei]

Are you dealing with harshness? I'd suggest you look into fork stiction before anything else.

 

[Mathieu9836]

Traxxion dynamics make a very good AK-20 cartridge kit... but priced about the same as Ohlins nix30.
I believe I recall they will reshim/revalve your stock forks if you are on a budget to fit your needs, too. If you call them up they can maybe help point you in the right direction.

Trouble shipping forks back and forth to canada?

Yes and no, i would prefer to do it myself to save on cost, but also to learn. I’m a Mechanic and most of the things i dont know is a knowledge problem, not a “am i good enough” problem.

Are you dealing with harshness? I'd suggest you look into fork stiction before anything else.

I replaced the all balls seals for the EO seals because i was having a faire amount of stiction to my taste, added fresh oil and i’m going to test again this summer. The issue i’m having is that when i ride at the speed limit the suspension is plush enough, but as soon as i send her, it become too soft, the front dive in high speed curves with bumps and become hard to control, the 10mm oil level higher is to try to compensate for that, hopefully compression will become stiffer as the stroke bottoms out

 

[Chuckster]

I don't think you're going to be able to have your cake and eat it too. If you're raising oil to prevent some dive, I'd think you're probably undersprung.

 

[matt365]

I don't think you're going to be able to have your cake and eat it too. If you're raising oil to prevent some dive, I'd think you're probably undersprung.

Agreed.

I'd check the racetech site to see what spring rate is proper for your body weight.

Stock valving seems to work well for me, but a gold valve and a new shim stack set up for your usage will help.

All Balls fork seals aren't very good. If they last a season, I'd be surprised. Good that you changed them.

I'd go back to stock oil height. Valving controls the flow of oil; IMHO, overfilling is a mistake.

Sent from my SM-G960W using Tapatalk

 

[Chuckster]

The gold valves were more about improving flow and eliminating the effect that valve body had on the damping. The BPF is sort of the same idea, so not sure if you'd even gain anything.

Oil height adjustments are fine as long as you don't go too high. Mine is run WAY below what the manual specifies (like 70% lower). But, if you raise your oil too high, you'll create pressures that were not intended for the fork and will likely blow out a seal. Not a good thing....

 

[JCW]

Fork oil and air gap is really good at adjusting amount of dive at full compression usually seen under braking. In cornering, the bike is not as close to full compression and might not have as much of an effect.

If your issue is with bumps, you are looking at adjusting the high speed compression characteristics of the forks. The high speed shims and spring can be adjusted to your liking... but I would talk to someone that specializes in this...
Talk to traxxion dynamics... they will definitely steer you in the right direction EVEN if you want a DIY and cost effective solution.
Cartridge kits can be DIY as well but not as cost effective unless you talk about changing setting for many different tracks.

This guy is one of the kings of suspension tuning as well... Motorcycle Suspension Tuning - Thermosman
I think he did a lot of work with the BPF's to make them work well without resorting to cartridges.
In some ways, cartridges are the easy way out...

 

[JCW]

Springs should be chosen for the correct loads you'd expect from your riding under cornering, braking and accelerating forces. Not so much to adjust compression characteristics...
Spring serve one main function- support the weight of the bike and you under load. you ideally want the softest spring rate to maintain contact of the tire to the ground. This is somewhat a difficult idea to understand... at least I had trouble. watch this... this is about cars, but applies as well to forks to an extent.

Why do racers typically use a stiffer spring? They corner harder, brake harder, accelerate harder and the load through the suspension is greater. This compresses the suspension more and the higher spring rate brings the ride heights back to the functional range of the suspension and more importantly sets the fore/aft attitude of the bike and determines handling characteristics.
Notice how I never mentioned sag... i think most racers/tuners don't even know what their sag numbers are.... they just know how much the bike "sags" under dynamic load.

I added this post just to say that dont pick springs to adjust your suspensions compression characteristics... it's not what they are for. They are there to support the bike under load.

 

[Chuckster]

Weight is a product of mass and the acceleration of gravity. When you corner hard, you're creating lateral acceleration. A racer will see a "heavier" load than most people on the street.

 

[Mathieu9836]

Thanks for the comments everyone, so if i understand correctly: i can't have the bread and butter with the stock fork, i cant have a plush ride at speed limit AND a suspension properly working at high speed with the same settings. Sag numbers are just numbers, i should focus on how the bike behave under heavy load and not what is the actual number ( considering i have good springs). According to RaceTech, the OE springs are 0.9km/mm and for ''track day" use i should have 0.95kg/mm, that being said, does having stiffer spring allow me to run a lower compression setting? This could mean the front end would not lower as much under load and compression damping setting could be set lower? Am i mixing stuff up? I guess i need to find a book about suspension tuning XD

 

[JCW]

You can have both a plush ride and control over bumps... to a point.
You have to adjust the high speed shim stack to adjust high speed compression for better control over bumps.
But best you speak to an expert...

On a cartridge you can just turn the high speed compression knob.

 

[Mathieu9836]

You can have both a plush ride and control over bumps... to a point.
You have to adjust the high speed shim stack to adjust high speed compression for better control over bumps.
But best you speak to an expert...

On a cartridge you can just turn the high speed compression knob.

I Think i will wait summer, then feel what the bike does and find a shop that does that for a living and ask them what i should get, if can just replace the shim stack or i should save and get cartridges.

 

[alexei]

I replaced the all balls seals for the EO seals because i was having a faire amount of stiction to my taste, added fresh oil and i’m going to test again this summer. The issue i’m having is that when i ride at the speed limit the suspension is plush enough, but as soon as i send her, it become too soft, the front dive in high speed curves with bumps and become hard to control, the 10mm oil level higher is to try to compensate for that, hopefully compression will become stiffer as the stroke bottoms out

On the stiction, there's individual stiction (fork legs alone, removed from bike), and there's the fully assembled stiction (with the wheels and triple clamp tightened), and the later deals with 'straightness' of the whole front end. Suggest you look into this. Grease the lower stanchion just lightly, and allow a thin coat on the exposed section, especially after a wash.

My stanchion is rainbow colored that looks like leaking seals, I don't mind it, as long as I care that it is lubed for the seals to travel happily.

From your description, I'd surmise (guess) that the fork is losing control when ridden aggressively.
Fork oil warms up just as shock oil, but slower. Once they do, they lose damping because warmer oil is less viscous. Suspension is best tuned when warm, and Dave Moss have a fork warmer for this purpose.

• Do experiment with the compression and rebound clickers. More damping = more control, and sometimes increase harshness, so there's the compromise.
• High end cartridges provides similar level of control, but less harshness. So we get more feel and feedback without the anxiety due to the harshness.

On my side, due to the climate (summer, all year long) we choose to go up on fork oil wt. i.e. 2.5wt to 5wt, or 5wt to 7/7.5wt, or even 10wt. Look around for fork oil viscosity chart for better understanding.

Use good oil for suspension. Silkolene RSF, Maxima fully synthetics are some of the consistent ones. Maybe the BPF is less susceptible to lesser oil quality but when oil travels pass the shims, there are microscopic events that affects damping. BFF is an even more wonderful system.

Spring rate is (almost) linear, but air gap is exponential as the fork is compressed. Too little air gap makes the forks too progressive far too early.

Oh, and another thing, what front tyre and pressure are you using?

 

[MadisonMotorsportUK]

Wow! You use 5w fork oil????? That's seriously light. I tend to run 15w or 20w fork oil and UK roads aren't in the best condition.

 

[JCW]

For some reason, fork oil weights are all over the place. One company's 10w might not be the same as another company's 10w. I know... it makes no sense.

I have a chart somewhere around here comparing probably 20+ fork oils and their measured viscosities. I'll have to look for it.

Might be able to google find it as well.