KDX220R suspension

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Oct 29, 2003
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#1
OK, so I pretty new to these KDX's but so far I am reading that the front forks are really kinda crap! I am a 215lb guy and I don't want them to be bottoming out all the time on me or washing out from poor control. Is this a easy fix to resolve this issue and how much am I looking at spending?
 

canyncarvr

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#2
Springs will run you around $70 or so.

You can run your weight thru the mx-tech site or some other if you wanna. For 215# you'll end up with something around .42 kg/mm. The race tech site generally gives you a spring that is on the high side of 'correct' (imo). Fredette seems to generally be on the lighter side.

There is a lot of preference to spring choice. If you're a hot-rod, 'A' class type, probably somewhat stiffer. If you ride for fun and don't fashion yourself some kinda mx-jumper guy, .42s should be close.

Put 'em in yourself in a few minutes. Change the preload to something that makes sense (not the 30+mm of the oem setup), maybe around 10-15mm or so.

Use 'search' to find the procedure if you don't know it. Ask if you can't find it.

The springs aren't crap...they're just puny. ;) Actually, they are pretty good springs!

Set your clickers! (oem setup is compression only. 'Washing out' is something controlled by rebound action.)

The correct spring is an excellent place to start.

Oh...and set your shock sag, too!

BTW, the oem 'H' model kdx fork spring is a .35kg/mm.
 
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#3
CC is right! You can set the spring rate correct for your weight and riding, but then your dampning is all wrong. Without rebound adjustment, it will be less than stellar performance wise compared to the rear suspension. The rear is about perfect for just about anyone once sag is set and you know what to do with the compression and rebound adjustments. If you need a heavier weight rear spring, (you are agressive enough rider) then you should consider swapping to a KX front end. Keep doing searchs here and you can get alot more info. Good Luck!
 

ChuckyBoy

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#4
I’ll admit it, I’m ignorant. But why is it so important to have 10 to 15 mm of preload as compared to 20 or 30 mm?

I bought my bike (98 220) with .38 Freddette springs already installed. I recently had my forks serviced and the technician said that the spacer was a “metal OEM looking piece”. After taking all the measurements, he was able to calculate that I have 22 mm of preload.

I am wondering if I need to replace the metal spacers with shorter pieces of PVC to reduce the amount of preload to the more widely accepted 10 -15 mm range. If someone can verbalize the pluses of 10 mm of preload versus the minuses of 20+ mm of preload I would appreciate it.

Thanks,
Chuck
 

canyncarvr

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#5
Exaggerate to make the point...

You have (example) 550mm of space for the spring and its hardware to fit. The purpose of the fork being to suspend stuff..why fill it up with metal tubes that don't do that?

Preload is applied to the spring to keep it 'tight' if you will. Why squeeze it so much? Yes, there is the issue of where in the stroke you want the fork to ride, as the valve body will be sensitive to such positioning. But, if you want to ride higher in the stroke, why not use the correct spring to get you there as opposed to filling the fork tube up with metal?

While others have their point of view, I've never bought any of it. The shants of a longer spring install (mine are 530 instead of the oem 470. Again, why use the fork to hold solid metal when it can hold spring?) of, 'It's heavier,' and 'the motion transfer time will increase,' hold no water in my opinion.

I've used the oem springs, .40 and .42 eibach springs in a 470mm lengths with varying preloads. The .40 XR springs (the longer ones) I use now are so far superior to the others as to be a slam-dunk when it comes to choosing a spring.

AND...the difference in the bike when I changed from 8 to 3mm (on the advice of a local tuner..) was a pretty big deal. Turned the bike into a joy to ride from a non-handling PITA that I was getting fed up with!

If you have the right spring (rate) you won't need 95mm of steel to make up some phony preload number.

.......imo and all that.



Cheers! ;)
 

ChuckyBoy

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#6
CC,

Thanks for your reply. I think I understand now.

When time permits, I'll try some shorter PVC spacers and see how that effects the handling.

Another question for anyone who cares to chime in:

Assuming I have the compression damping clickers set "where I like it", will decreasing the preload from 22 to 10 mm require me to fiddle with them (clickers) some more?

As always, thanks again.

Chuck
 

canyncarvr

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#7
Springs are not linear (regardless of the argument of some that have disagreed with me. They're just wrong. ;) ). As a spring is compressed, its rate increases and its capacity decreases. Granted..in the range of a 22mm vs: a 10mm preload spacer, that change amounts to about diddle.

Certainly the compression characteristics will change when you change the preload. Whether it's enough of a change that you will even notice is another matter.

:think:

Probably not.

Besides, there are some finer points to compression settings that are commonly missed. OK..to tell the truth, I say that because I missed them for a long time. Generally, compression setting is done based on how the forks handle big stuff, but not set so tight as to chatter your teeth on the small stuff.

But compression setting also has a huge impact on rut tracking (not being able to steer out of one) and uphill tractability (going over roots and rocks on steep slopes and still keeping the wheel on the ground). Largely a personal choice I'm sure, but three clicks out (less compression) from what I'd thought was 'just fine' resulted in a much better performing suspension.

I'm saying that leaving your clickers alone and reducing your preload will likely be a good thing.
 

Braahp

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#8
Some will argue all day over preload but decide what is best for you. Its done one way as much as the other. I tried many setups and decided I liked a little lighter spring (.39kg) with the stock metal preload spacer. Mine figured out to be 22mm also. Ends up being stiffer than most .40kg setups. I have a handy dandy fork spring preload Excel calculator I will send you if you'll send me your email. You can plug in different variables and see the different stiffnesses throughout the travel range.
 

ChuckyBoy

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#9
Hey Braap, thanks for your input. I'd love to take a look at the calculator spreadsheet. Please send it to: chuckkdx*hot.rr.com . Please replace the * with an @. I don't want a bot harvesting my addy!

CC, thanks for taking the time to help me understand preload, spacers, and springs and how they all work together to effect handling characteristics.

KDXFRK, I apologize for accidentally hijacking your thread. :whiner:

Ride on,
Chuck