CRF spring rates

C

clw

Member

Dec 29, 2000

239

0

• Nov 4, 2002

• #1

Looking through my new Dirt Rider and noticed that the CRF450 has a 0.47 fork spring rate. I know this is old news, but why is it so high?

It's a light bike (only 12 lbs. more than my YZ w/0.43's, that's the same as 2 gallons of gas) plus it doesn't have much engine braking. So, what am I missing?

 

Jeremy Wilkey

Owner, MX-Tech

Jan 28, 2000

1,453

0

• Nov 4, 2002

• #2

CLW,
Whats even more scary is that with the added effect of tghr ICS we are way above the .47 rate, more like .49!! The bikes uses the diferent rates beacuase they have very diferent chain torque reqirments/and characteritics. For the bikes to balence out the the fork springs must be way stiffer. Also I'm quite sure that Honda Knows that largr rider demograhpics will come into play as well. If you spring the bike for a rider weighting in at say the same as a 250, then the diferences are not so substantal. As we've learned more abou these next generation forstrokes the rates we reocmend have gone down and the valing has changed signifcanlty as well. Its a learning process, and most guys started by treating these things like XR 650's LOL.... Anyway thats a start!

BR,
Jer

 

T

teggers

Member

Nov 30, 2001

20

0

• Nov 9, 2002

• #3

Me and shockdoc have gone to .50 on the front on my 03 - 450. I weigh 180 and am a vet pro.

 

S

shockdoc

Member

May 3, 2001

327

0

• Nov 9, 2002

• #4

Along with a lighter ICS spring.


doc

 

Jeremy Wilkey

Owner, MX-Tech

Jan 28, 2000

1,453

0

• Nov 9, 2002

• #5

Thats still really Stiff and uses TWO spring changes.. What you got up your sleve with that course of mods Doug?

 

S

shockdoc

Member

May 3, 2001

327

0

• Nov 10, 2002

• #6

Well, Tims bike was 1 of the first ones I did. I didn't have any shims yet for the new 33mm comp. piston. We really didn't think the valving was so bad, but it just wouldn't settle in for the corners so good but yet started bottoming when broke in. I used a lighter ICS spring and then the bike started setteling and cornering good but started bottoming more. More oil made mid-stroke harsher. Then we went to .50, dropped the oil slightly and seem to have the best of both worlds. Thats how we ended up but I could probably achieve the same results a little differently now.


doc

 

F

flynbryan

~SPONSOR~

May 22, 2000

1,066

0

• Nov 11, 2002

• #7

guys ive got the 02 crf450 and cant get the front to settle in the corners right. reading this column got me thinking about it. the local suspension guy i talk to says that that i should go softer on the fork spring rate(i weigh 174 before gear)im currently running the .47 (stock)springs and was wondering if jeremy or others could give me some advice. the tuner also told me that w/ most amatuer riders he works with he does a mid-valve adjustment(i believe he said he sets it like a bleed off) because amatuer dont need as much resistance in the middle of the stroke as showa offers w/that set-up. any comments on this are appreciated, mostly the spring rate is what im looking for right now though. thanx! :worship:

 

S

shockdoc

Member

May 3, 2001

327

0

• Nov 11, 2002

• #8

I would have your suspension tuner check your rebound/midvalve piston nut. Many of the '02's came loose which sped up the rebound some. Make sure thats all working good and then I might consider installing a slightly softer ICS spring.


doc

 

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flynbryan

~SPONSOR~

May 22, 2000

1,066

0

• Nov 11, 2002

• #9

ive heard of that prob as well. w/the ICS spring ive heard both good and bad things about changing that spring rate. also does the ICS spring act as the preload for the fork springs?

 

Jeremy Wilkey

Owner, MX-Tech

Jan 28, 2000

1,453

0

• Nov 11, 2002

• #10

Byran,
There is no need to replace the ICS, its just one more thing for tuners to sell. Fourstrokes need more preload. We've got a string in here if you run a search on the ICS. You should defienlty go down in spring rate however. Forks and shock. Midvalve mods are very critical so thats good your tuner us up on that.


To Clarify the ICS adds prelaod effect in the static postion, and then flat line contributes about .02 to the overall rate.

BR,
Jer

 

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flynbryan

~SPONSOR~

May 22, 2000

1,066

0

• Nov 12, 2002

• #11

Thanks Jeremy, but heres the pickle..... the fork is indeed to stiff for me, but I went to a 5.6 rear spring for the shock because i was at the end of my compression adjustment. i have my race sag set properly at 100-97mm and i keep aware of my riding position and ride over the front of the bike. I was thinking of going to a 0.45 or 0.46 for the fork springs. By the numbers will this be out of balance? right now it already feels like its out of balance with the shock being the softer of the two. thanks for your help. should i put this in a new thread as not to take up these guys string? thanks again.