996 forks springs

Started by jerryz, December 04, 2012, 12:16:00 AM

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jerryz

The 996 forks are on my S4 they have improved the handling massivly over the standard forks but .......the bike is a road bike used on very bumpy roads so a plush fork is needed .

what is the standard nm weighting of standard 996 fork springs ? 8.5nm 9.0 nm or 9.5nm as the springs in mine are way too hard i have them set on ZERO preload and forks still to hard oil is 7.5w and 140mm airgap

compression set at 4clicks and rebound 13 clicks bike handle fine but crashes over bumps seems to me and others who have tried the bike that springs are way to strong ????

bike has Ktech revalve kit and possibly Ohlins springs supposedly 9.0nm but i have my doubts about what spings are really in the bike I do have a set of standard 996 springs .

FrankenDuc

Are you sure it's the springs, and not the oil level or the midvlavle's compression flow restriction causing your troubles?
What is the oil level currently at (how much air gap, with the forks fully compressed, between the oil and the cap)?
If you were to wheel the front end of the bike onto a regular drug or department store scale (with you on it, in your normal riding tuck), what would the scale say?

Another question - what is your static sag without you on the bike, distance between full unloaded and load of the bike only, and what does the front end weigh using that dime store scale, again, without you on the bike?  This will tell you your real spring rate.

We're neglecting the topout spring here, but it's an SBK fork right?  Topout spring should be short and stiff, i.e. negligible.

The spring alone should not make the forks sooo harsh....
"hammer to fit, paint to match"

FrankenDuc

BTW - when you're trying to figure out your stiction, spring rate, etc., it's best you test with your clickers full soft

I've got about 0-3mm of stiction on my forks with compression and rebound full soft, depending on the sunspots, moon phase, atmospheric pressure, and many other irrelevant metrics.  At my normal settings, my stiction goes to ~20mm...
"hammer to fit, paint to match"

jerryz

oil air gap is 140mm it was only 110mm from ktech after the rebuild , when i told them how harsh the forks are they said raise airgap so i drained  some oil , static sag is 12mm .

preload is zero ,fork spring appears to be 9.25nm on  local ohlins agent test rig  test rig .

the invoice from Ktech says the springs are 9.0nm but i dont believe it as the preload is now set at zero , I did actually ask for 8nm springs but they said they would be too soft , now i am not happy with this situation as the front end is painful ,I did try some hyperpro 8.5nm progressive springs but they made the bike dangerously unstable at high speed so linear springs seem best , just need softer ones .
if i can source some 8nm springs from somewhere  i think it would be worth it

the compression and rebound damping circuits work very well the bike is fine of racetrack smooth roads but in real world its nasty

when a customer spends $800 on a revalve and spring setup you would think they would build it to the spec I require????

ducpainter

According to Race-Tech stock 996 springs are 1.0kg/mm

Depending on your weight you could go anywhere from .8 to .9 on a monster.

My experience is that ride harshness is generally a function of damping more than spring rate.

I think your stack needs to be modified.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



Speeddog

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Reseda, CA

(951) 640-8908


~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

FrankenDuc

A useful conversion - 9.81 Newtons to 1 Kg (at sea level :) ), so 9.25N/mm is ~0.94Kg/mm

Yes, not to get too personal, but what do you weigh?  I won't judge you by it... I promise!...

At my ~210lbs, on a watercooled Duc, ~0.90Kg/mm on the front feels nice to me on some pretty gnarly road surfaces.  On the track, I'd add 0.05KG/mm easy, maybe 0.10Kg/mm...  But, if you're wrists are not happy (not to say you're gripping the bars too tight... no matter how hard you try, if the bars are all over the place, your grip gets tighter and your wrists hurt more... just plain instinct...), drop some...  My experience, around 0.85~0.95 Kg/mm, the springs are actually too soft for hard track use, but seem very harsh for road use.  This isn't actually the springs, it is the damping...

The Showas are pretty well damped, actually, relatively speaking... VERY well damped, to be honest... But if you don't like the damping you'll have to find your way through the mess... If you can find a good suspension guru, they'll help you through it, including softening the shimstacks for your weight/damping needs, lowering the shim thickness from 0.15 to 0.1mm on the first two to four shims in the stack on both compression and rebound, to match your lowered spring rate, etc...

Most important though, what are your complaints.. just how exactly is the suspension working well for you... what are you not complaining about. What is the good, along with the bad?
"hammer to fit, paint to match"

jerryz

as of today i weigh naked  73kg (161lbs)    so in gear lets say 175lbs the bike had a new Ktech shim stack put in with the new springs specially set up for my weight and i wanted and specified a soft ride due to the roads in Thailand , i did ask for 8 or 8.5 springs  but the ones thay put in are 9.0 and when tested recentlky by local ohlins agent on his test rig they were 9.25 so it seems they failed me for $800 work , unfortunately there is no one in Thailand who can work on these forks  so if i want more work done on them, its back to UK , not convieneient or easy .

to be honest if i can source some 8 or even 8.5 springs they are not much money $100 it would be the best option to experiment , I am happy with the adjsutment and sharp accuracy and the very precise adjustabilty of the KTech valve stack , just the fact that the nike is on zero preload and too firm makes me think the springs are too hard .

I asked ktech by phone why they put in 9 springs instead of 8 or 8,5 as they list them , they said thay dont have stock , neither do ohlins ,  so although companies list them they seem rare .

ducpainter

At your weight I'd use .85 springs.

How about race-tech?
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



jerryz

Quote from: ducpainter on December 05, 2012, 07:08:12 AM
At your weight I'd use .85 springs.

How about race-tech?

I will give them a call .i still reckon ,80 would work best here as the roads are seriously naff also the bike is more of a sports tourer now than  balls out bike comfort is priority

Speeddog

The OEM Monster S4 springs are ~0.85.

IIRC, they're a good bit longer than the SBK springs, but shortening the spacer is easy.
- - - - - Valley Desmo Service - - - - -
Reseda, CA

(951) 640-8908


~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

ducpainter

Quote from: Speeddog on December 05, 2012, 08:04:02 AM
The OEM Monster S4 springs are ~0.85.

IIRC, they're a good bit longer than the SBK springs, but shortening the spacer is easy.
Aren't they progressive though?

Quote from: jerryz on December 05, 2012, 07:18:12 AM
I will give them a call .i still reckon ,80 would work best here as the roads are seriously naff also the bike is more of a sports tourer now than  balls out bike comfort is priority
I live in NH. Our roads aren't known for quality. .85 works for me, but try the .80

I still think the guys that built the forks used too aggressive a stack and you need to 'soften' it up.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



Speeddog

Quote from: ducpainter on December 05, 2012, 09:32:58 AM
Aren't they progressive though?
I live in NH. Our roads aren't known for quality. .85 works for me, but try the .80

I still think the guys that built the forks used too aggressive a stack and you need to 'soften' it up.

S4, S4R, S4Rs and S4Rt all have linear springs.
Not sure what the Rs has in the Ohlins, but the others are ~0.85.

+1 on a too stiff stack.

My limited knowledge of the K-tech is that all of the compression damping is in the base valve.
- - - - - Valley Desmo Service - - - - -
Reseda, CA

(951) 640-8908


~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

FrankenDuc

I keep forgetting you have the K-tech's - I've read really good things about them.
I hear you on spending $800 already though, I'd definitely be a bit miffed having spent already some good money and not getting what I wanted out of it.
RaceTech should have down to 0.85Kg/mm, I've picked up two sets of 0.85's for different bikes and they both showed up at my door right away.  Perhaps they can source lower rates on request?

Definitely I would rebuild the shimstacks lighter if swapping out to lighter springs and having trouble with a rough ride - the adjusters primarily control your low speed damping, the shimstacks have much more of an impact on the high speed damping:
- during bumps and sharp impacts, damping force will be dominated by the high speed compression valving
- with a lighter spring, there's less rebound force from the spring itself, rebound damping needs reduced across the full suspension velocity range
It wouldn't hurt at all to try the spring change alone, but I think you'd get a lot more out of the forks by getting into the shimstacks.

I know international shipping to send the forks off for work gets costly and time consuming and import/export paperwork can be rough to deal with, and it's definitely a bit of a commitment digging into the shimstacks yourself.
If you dig in yourself, you'll learn a whole lot from the experience. I'd do some research, from K-tech, from here and other forums, from anyone and anywhere I could. Otherwise it's pure guesswork. Just like when adjusting the knobs, big changes you could make the suspension worse, even unstable, but go slow, iterations of small changes each build, test ride with caution, and it'll be all good.

[beer]

"hammer to fit, paint to match"

jerryz

I spoke again to one of ktechs main technicians , and he says that it does seem that my forks are not working properly and that the spec that i asked for was probably not delivered ,(issues with the ex staff member who prepared my forks)

I may be able to modify the shim stack myself if needed but he also said a much softer spring was required ,and we are trying to source an .8 also lithter oil  ,it seems that 10w oil might have been used  , there is no way i can get these forks back to Uk for at least 5 months as they have to be carried in my luggage ,in and out of thailand if i ever want to see them again  and I am off to work next week anyway ,

oh well its an on going project