I´ve been researching recommended springs for me (220 in gear) and my 2011 yz250f. And the recommendations vary alot from tuner to tuner!  Öhlins chart says 58N/mm. Mx-tech 55N/mm(5,6kg) "other" tuner 54 or 56 if I´m very fast..   Racetech 55N/mm (5.6).

Race sag seems to be the same 100+-5mm there about. But RT says 20+-5 free sag and Öhlins 30+-5mm.  No wonder the recommendation differs!  Who should I "trust" ?  I just want the bike to handle like it´s intended to do.
Had 5.0N/mm on my 09 450F in the forks so I combined one 5.0 and one 4.5 for a 4.75N/mm in the fork. And the 60N/mm spring from the 450 just to try! but to my surprise I get 105mm race sag in gear and 33mm static...  Which according to ohlins way of measuring indicates everything is great!? but RTs 20+-5 indicates its WAY stiff! I had guessed on and almost ordered a 56... Now I dont know.

Its very stiff compared to stock, but stock was VERY wallovy... LSc Clickers went from full hard to almost full soft but I havent done much testing, fork is soft initial stroke but doesnt bottom out.

The spring you have now is good,  30-35mm no less on a4 stroke,  on a 2 stroke 25-30 is fine

ok. I´ll just ride it some more with the stiff spring and evaluate. The numbers dont lie although it felt like a big jump from 52 to 60 N/mm!   Is it a known "problem" that the rear shock has light rebound damping? Feels that way. Think I set it at 2 out last time at the track.

Yes it needs way more damping in reb, 2 out will also  make the comp feel harsh

25mm free is what works for me.

Static sag and rider sag should be based on a percentage of actual wheel travel.  Front and rear.  You should have no more than +-3mm variance to be correct.  Most of the online spring calculators are very wrong.  20mm on a modern bike is crazy wrong.  Most modern bikes are in the 35mm range.  You should have 11% of avaliable travel in static sag ( I prefer +-2mm variance) and no more or less than 33-34% of actual travel in rider sag. (I prefer 34% with any variance going to the lesser side).
Be sure to also set your fork sags too.  What works on a MX / SX track on spring rates are usually way off for a offroad rider .  I like rider sag of 25% of actual travel and 14% static sag.  Also +-2mm variance.  MX riders have berms to help with turns and while stiff fork springs help with deep whoops they really make the bike suck at turning on flat ground.  Also too stiff a fork spring will make riders run too much preload on rear to try to transfer some weight to front  to help with turning.  This makes for a very harsh ride overall.

Dwight_Rudder, on 02 June 2012 - 11:43 PM, said:

Answered like a boss.....

What if, as in my case, I race cross country, A level rider, I weigh between 215 an 230 depending on time of year and trining/riding, bike is a 2011 yz 450,

So I change the rear spring as I cannot get correct sag numbers, but get the correct fork sag numberswith stock springs, would the bike not be unbalanced ?

Or is a balanced bike one that has correct sag numbers, not necessarily spring rates that correspond

mog:  do you have a rebound stack that works and are willing to share?       I´ve noticed that its not good having the clickers closed or nearly closed..

Dwight: thanks for the excellent explanation!  I´m spot on in the rear then.  The front not so much... BUT, I think the "all-balls" seals arent the best ones out there!? Dont seem to last and doesnt slide smoothly. SKFs are expensive but I think I´ll give them a try once these start to leak. My static fork sag is 15mm and race is 50mm. I´ll have to recheck as I forgot to relieve them from airpressure.

Stu2:   I´ve been thinking about that as well!  Since I´ve gone from 52N/mm --> 60N/mm in the rear and only 4.5-->4.75N/mm in the front. But from my limited testing I feel its rather stiff then soft up front.

jonsson_, on 03 June 2012 - 10:32 AM, said:

It should have more than 15mm static with stk springs. I would bet you have a lot of stiction either the seals/bushings (esp. if the bushings weren't replaced when the seals done) or r/s fork bound up.

I almost always try to set rear sags up as close to 35/100-105 as possible. Except KTM's & mini's of course.....

doc

If you add 2 *40.3 to the rebound it should get you close

do you mean 36.3's

No its the 2011 shock 50mm

Shockdoc:     15/50 is with 4.75N/mm, stock springs are 4.5.   Previous owner had ohlins ttx front and rear. Suspension is supposed to be 10hours since new.   I changed one of the seals when I replaced the spring(minor leak).
Forks are aligned.

mog: Thank you!  I'll try that and see how I like it.

mog:  I checked the stock rebound stack and i must ask if you´r sure about the 40mm shims?

stock stack:
5 - 36.2
28.12
36.25
34.25
32.25
30.25
28.25
26.3
24.3 b

havent opened up the shock but 36--> 40

Comp side has 40mm faceshims though.

Edited by jonsson_, 05 June 2012 - 10:41 AM.

Yours is a 250 not 450 , you shiikd have said ;-)

Even for a 5.0 rear I would be changing the lower shims in hs to 0.3

Hahaha      

I think I´ve seen a rebound stack posted earlier with all the .25s swapped for .3s. Maybe that was you posting  

whats the opinion on the 12 kx450f suspension?   I was very surprised when i testrode a friends bike and the suspension is REALLY good! Its difficult to compare as I´m alot faster on my own 250F but the Kawi is plush yet with good feedback. soaks up the bumps VERY well....  Looked at the kawi valving and the mid is alot stiffer then on the Yam and more rebound.  The 12 kawi is SO much better then the 09 he had before! Light and nimble for a 450.