spring rate

Questions and comments about converting to beefier forks..
Post Reply
sluggo69
Member
Posts: 46
Joined: 10:56 pm Jan 03 2005
Country:
Location: southeast,La.

spring rate

Post by sluggo69 »

i have a set of 03 kx250 forks(.44s stock) on my bike . i am 200#'s and i ride alot of technical trails that are full of roots,sand whoops, ect.. im running at damn near full soft on both ends and they still rattle my teeth.they take the big hits (drop offs ) very well but kill me on the large and small squared hits. i was going to have a local tuner revalve them but decided to try changing the springs to .42s to see if it can make a difference before i dump several more hundred dollars into them. i can get a set of .42s for 80 bucks.will this make a difference? im not sure i want to put more money into this bike because the great pumpkin is looking better and better each day. ie.300xc-w
03 kdx/kx200... my lil woods weapon
07 zuki ozark250...xmas present for my son
User avatar
Jeb
Gold Member
Gold Member
Posts: 1894
Joined: 08:01 pm Jul 14 2006
Country:
Location: Cincinnati / Northern Kentucky

Post by Jeb »

sluggo - Try using the spring rate calculators on racetech.com and mx-tech.com to compare. Swapping to lighter springs might be the way to go - certainly the way to go if both sites calculations indicate so, but I'll bet its worth a shot trying a few things first (if you haven't already). I'm no pro at this but will offer some food for thought only because I've been spending a little time "tuning" things a bit and have managed to improve things from when I first did my USD conversion . . .

What is your fork oil level set at? 115mm to 125mm seem to be what works for lots of folks that ride predominantly in the woods. I followed the advice and lowering the fork oil level seemed to soften things up some for me on the small-bumps side of things.

If you ride hard for a while, relieve some of the built up pressure by momentarily opening the air bleed screws. Better yet, get some of the push-button air bleed gizmos - no screwdriver needed ($28).

What you described as "full soft" - rebound and compression fully counterclockwise - will be best suited for only specific conditions (and I'm not sure what those conditions are BTW). Having rebound adjusted incorrectly can give you a rough ride whether they are set too hard/fast or soft/slow depending on where/how you're riding. For where/how I predominantly ride, my forks seem cushier with the rebound out about a dozen clicks (I think about half-way out) and compression 2 clicks shy of fully out. The forks are a tad stiff and I may eventually spring for some aftermarket valves after I've fiddled some more, but those settings seemingly work best when I'm riding through a lot of small but square-edged, rough stuff. 'Still not done, but things have gotten better.

My point isn't that my settings will work for you; rather, understanding that rebound and compression have specific functions is key to maximizing that suspension. Here's a link that describes it best, in my opinion (click on the "Suspension Knowledgebase" links at the left of the site):

http://brucessuspension.com/

Good luck! It would be interesting to hear what you do and how it works, you might end up further along than I am!!
"No farmer ever plowed a field by turning it over in his mind" -George E. Woodbury

CLICK FOR PICS!
sluggo69
Member
Posts: 46
Joined: 10:56 pm Jan 03 2005
Country:
Location: southeast,La.

jeb thanks for the info

Post by sluggo69 »

im going to install .42 springs and run the fork oil height at 115 mms. i will report back with the results
03 kdx/kx200... my lil woods weapon
07 zuki ozark250...xmas present for my son
User avatar
80elkster
Supporting Member II
Supporting Member II
Posts: 135
Joined: 08:43 pm Jan 01 2006
Country:
Location: Maple Valley WA

Post by 80elkster »

Sluggo;
Dude the lighter springs may make the front end slightly softer, but they will want to dive when you hit brakes. You have to remove a few of the valve shims in both the base and mid valves to get rid of the harshness over the square edge stuff. Those forks are set up from the factory for doubles and triples, fast woopdees and so on. Bradf is an excellent resource for tuning those forks for the woods. Try a search in this forum filtering on his name you may also try PMing him. My son and I revalved a set of USD KX250 forks that we had swapped onto an 05 KDX200. We ended up taking out quite a few shims from the base valve and a couple from the mid. You may also want to disable the bladders along with modifying the restrictive barriers. Overtightening the forks in the triple clamps (over 12 in-lbs) can cause "Stiction". Misaligned axle and front wheel can cause binding. There is a very specific method to aligning/installing the front wheel, axle and forks into the triple clamps so that there will be minimum "stiction" and binding. All the things I've mentioned and probably some that I haven't contribute to poor fork performance. Please be patient and persistent with your forks, they can be valved to work excellent in the woods. The difference between the 46mm USD forks and the stock forks is night and day. The difference between stock USD forks and valved for the woods is just as awesome.
Oh and we ended up with 2.5 wt fork oil in them at 120 mm from the top of the forks. :rolleyes:
PM me if you would like a copy of an axle alignment pdf file I have. Bradf has sent me some fork mod info also but I would rather you ask him for that.
06 DR650 Farkled
91 WR250 2T
00 300EXC (Sold)
79 XS850 (Sold)
79 CR250 (Sold)
78 IT400 (Stolen)
75 G5 100 Kawi (Gave it away)
73 F7 175 Kawi (Sold)
70 175 Brigestone (Recycled)
05 KDX200(Son's)
93 KDX200
75 KT250 Trials
250 Quads
Just glad to be ridin!
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

Sluggo,

Let me know if you want to sell those .44 springs. I have '03 KX125 forks on mine. There were no bladders on them that year from what I understand. My forks were bit too plush before I rebuilt them. They have Gold valves in them with a dual stage valve stack set up for a novice level MX dude. I'm just telling you this to show that you can tune those forks to work for Gitanic Free-style jumps, all the way down to super plush for a lady to ride. I haven't really gotten to ride since the rebuild so I don't know if they're any better yet.
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
Post Reply