996 forks springs

[FrankenDuc]

  I'm in rapid fire documentation mode for work right now, I appear to be taking it home with me

Think you've got the right idea though, less talk and more ride 

[MonsterHPD]

No need to be diplomatic here, we're just trying to find the best starting point for choosing spring rates.
I've also been down the route trying to make sense of static and dynamic loads etc, but at least for me some basic professional advice when I bought my Öhlins fork ("use 8 N/mm spings ..."), and what has proven to work on trackdays as well as road riding, was the quicker route.

Of course one can not match a precisely defined bike sag with a precisely defined rider sag when the bike weight is pretty constant and rider weights vary, sometimes wildly, no matter what spring is used.

However, juggling spring rates and pre-load and working with sensible ranges for the sag values mentioned has proven to give results most people are happy with, if only because what they had before was wildly off. Really quick riding might require a more scientific approach; I'll probably never know first-hand   

That said, your thoroughness, Frankenduc, really impresses me. I've done a lot of thinking about this and related things, but I think you take off where I let go 

Jerryz, sounds like you have some interesting riding surroundings, and not least, climate. It's -8°C here now ..... have a nice trip!       

[jerryz]

HPD and Franenduc what do you guys do for a living , i wish i was less isolated here but i do spend a few months of the year in Uk riding my M750 and 750ss there , thaty have nonadjustable forks and work fine ,amazing as the s4 has fully adjustables and all they do is pose questions .

i have often enjoyed riding in California and oregon in the past

[MonsterHPD]

HPD and Franenduc what do you guys do for a living 

I spend too much time at work, really. Maybe I should sleep some more 

[jerryz]

had a bit of a breakthru today  , my friend Dom came down from Bangkok on his hyabusa ,  he brought some 5w motul factory line fork oil so we drop the forks again and changed the oil

so bike now has .85 spring 5w oil , whilst we were putting it back together  I was stuying my extensive notes from over 7 years on modifying the nike when I noticed an anomaly ......doh!!!!!   ,BUT what i had forgotten was that I used to run the Old forks 15mm lower thru the forks for better turn in , but they were so flawed in damping that i eventuall replaced them with the modified 996 forks after 5 years.

the old Standard  showa S4 forks were 15mm shorter than the 996 forks so when i fitted them i set them 15mm thru the triple clamp plus 5mm=  total 20mm  but the bike is sitting 10mm higher than i liked it before   ( so I have had a massive brain fart)  no wonder there may be not enough weight over the front whell and also trail is too much so turn in will be heavy .......DOH!!!!

any way we set the forks another 10mm lower so in reality the forks are -15mm now  , to compensate i reduced rear compression also by 2 clicks

The rain had stopped so we went for a 50 mile ride  after  10 mies i stopped for gas an felt that the bike was much nicer especially in the turns at all speeds , no running wide or understeer very flickable not like before , also front felt like it needed mor rebound so 2 clicks more  now 12 in   compressionwas upped from 2 in from softest to  3 in   and i put 2 turns on preload

we rode on and the bike feels much better , the 5 w oil has helped a lot ,i can feel every thing the tyres are touching front and back also no slides from the rear now at all even on wet roads.

the only negative is high frequency vibrations on the handlebar thru the forks , not engine related I have gel grips but may be need heavier bar weights ?

so a basic  error by me on geometry has been blighting the bike ........IDIOT ... forks may still benefit from damping or spring change  as i think they could be a bit more compliant or is it the handlebars

cheers jerry

[MonsterHPD]

Nice to hear you got the fun back 
I did same sort of thing when I installed my Öhlins which are also longer than the stock Showas and the bike steered like a shopper. Pushing the fork legs up through the triples cured that, and I also run the fork legs some 10 to 15 mm lower than stock and the bike steers quite OK.     

[jerryz]

This morning I picked up some really heavy nicely finisged Stainless Bar end weights the old ones were feeble a few grams thes boys are 2 oz aboy 60 grams each , made a big difference to the vibes  ,

no rain today so gave the bike a real test. thrashed her hard on my favourite roads , steering is perfect , can lay the bike over at extreme angles  and flick side to side, tracion good  ...awesome

Bad is that .low spped damping is still a little harsh BUT high speed above 60 mph up to 130mph  the suspension is perfect even on very bad roads .

tarmac roads are pretty good but washboard style concrete roads are a little bouncy until over 70mph then they get a bit more tolerable

not sure how the damping circuit on Kspeed  valve stack works or the 996 or wether more can be done to dial in the low speed damping
front tyre is nearltt finished  so that cant help

a great day out today 80 miles  of perfect biking

[FrankenDuc]

nice to hear!!!  

So, yeah, you're probably a little tight on the low speed damping, which is not necessarily a bad thing at all - if you can tolerate what it does. It helps you with brake dive and squat under heavy acceleration, deep in corners the bike stays on its line way better no matter what sort of nasty things you're doing on the controls...  You can change that pretty directly with the compression clicker.  Having a lot of LS compression damping does make a pebble on the road more noticeable though, and IMO as long as I don't mind that and it's not bucking me off the bike it's all good.  

The higher frequency stuff is probably due to running your clickers nearer to closed and overall having higher low speed damping - you could make that go away, but it's sort of like one of those relationship compromises...  Although, I did come up no too long ago with a midvalve compression shimstack that, in conjunction with the other stacks in my forks, would cause a small wholly undamped oscillation at a certain frequencies (~2-3Hz) if perturbed the right way... I could lean off the bike and watch it, the wheel would never leave the ground and it would never happen under cornering loads so I thankfully always had very good control, but eerie still. If you notice something bumping you at a constant rate while you're on a smooth road, it's probably good to take a step back and look at it

How are the bar ends working out, do they help?

I've got GXSR forks on my Monster, they're longer than stock by, oh, an inch or so, I drop the front a good half inch or so triples to forks and raise the rear about the same to get the turn in I like.  Maybe a little higher on the front than the rear for me.  Love the extra ground clearance.  You can do the similar for turn-in/stability with preload, turn down the front some or up the rear some to get quicker turn in...  Opposite makes you push a little harder to keep it leaned over, which gives a little more of a stable feel.

I spend too much time at work, really. Maybe I should sleep some more  

Concur!!!
I'm an Electrical Engineer, for many years I did a lot of analog closed loop control system designs at chip and board level - power supply/conversion, PLL's, test and measurement - and loved it. That's probably why I enjoy to wholly and completely overthink on suspension - it's open loop, discounting the rider's inputs but still a control system. The mechanics are vastly different and not what I'm used to (kind of wish I hadn't slept straight through Statics and Dynamics in school), but the concepts are still very much the same. And control.. Who doesn't like it

[freeclimbmtb]

I couldnt have found this thread at a more helpful time, but I really dont want to thread jack here...  So Ill wait for someones go-ahead before drawing the thread to my own questions...

[Speeddog]

I couldnt have found this thread at a more helpful time, but I really dont want to thread jack here...  So Ill wait for someones go-ahead before drawing the thread to my own questions...

Fire away!

[freeclimbmtb]

Not the OP...but Ill take it. 


Right now:
Bike: 2011 Monster 796, for this discussion call it stock. (except clipons which affect weight bias, and call it 10lbs of shed weight)
Rider: 5'6", 132lbs in street clothes...say 147 in gear.

Changes to be made when the triples arive:
Ohlins from an 1198R (stock forks to the best of my knowledge), 1098/1198 brake/clutch controls, IMA special parts full replacement triple trees and adjustable clipons.

Heres why:
I'm a skinny guy.  Ducaticant possibly have had someone smaller than me in mind when they built the 796, yet I've bottomed the forks out on potholes more than a small number of times in the last 12k miles. It dives super hard on hard braking, and just genrally feels crappy.  Ive even had friends comment that my fork is always moving, yet when they sit on it are in disbelief as to how short the range of travel seems to be.


NOW...  based on what Ive read above, a 8.0 N/mm spring should be about right, (at least for street, perhaps an 8.5 for track?)  Ill deal with the rear later.  But thats about all I can contribute to setting it up.  (owing to lack of experience, not lack of understanding...I learn more by doing than reading)  I dont know what to do about valving or oil, or really even where to start with rebound/compression adjustment. (a product of having always been on a non-adjustable suspension.)

The up/down side...Ive got plenty of time to get the project done in the winter months, but no way to test/tune until the weather changes. 

[Speeddog]

You're on the right track with the 8.0 spring.

I suspect you'll want to soften up the valving.... but not having the forks in my hands, that's just a suspicion.

I recommend staying with the standard Ohlins fork oil, #1309.

I *think* those forks will take the 04745 series springs, but verify prior to buying....

[freeclimbmtb]

Ok.  More than likely I will go with the 8.0 springs, I will verify with an Ohlins shop before buy the springs.  That should get me to a point where I can at least ride to Boston for a tweak and tune session with the guru down that way.


Now briefly on the rear.  I know the DU737 is THE replacement for the sachs unit I have, and Ive heard good things about it.  Now, what about a superbike rear end as well?  the 796 and 848 share the same swing arm, so is the shock an option as well?  (pending clearance issues with the external reservoir)

[Speeddog]

796 and 848 swingarms aren't the same, 848 has a linkage, 796 is direct-connected to the shock.

I don't think any of the shocks with a piggyback reservoir will fit.

[freeclimbmtb]

Gotcha.  Just looked at a blowout diagram and had the DOH moment.