Front Spring Rate Question

Questions and comments about converting to beefier forks..
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stnd
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Front Spring Rate Question

Post by stnd » 02:41 pm Sep 29 2020

Hi,

I have an '02 KDX220 with an '01 KX125 front end. I am 220lb without gear and am wondering what spring rates I should be running in the front. Originally when I did the swap I used Race Tech's website to calculate based on my riding for a 2001 KX125 and got a number which was close to the .41 springs that are in the forks.

After reading some threads on here people were mentioning heavier springs at my weight and now I think I should have calculated using a heavier bike on the Race Tech website.

Using a KX250 the spring rate comes up at 4.3 or 4.5 depending on Novice or Intermediate Trail/Enduro.

My shock spring is 5.4

Can anyone confirm whether .41 in the front is too little for my weight?

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Re: Front Spring Rate Question

Post by KDXGarage » 05:10 pm Sep 29 2020

0.46

Go check your rate on a YZ250X, which is 0.44 stock and weighs about 218?? or so, which is 15 pounds less roughly.

You are not riding a 2001 KX125, so no need to check that.
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Re: Front Spring Rate Question

Post by SS109 » 08:29 pm Sep 29 2020

I run spring rates at what it would be for a normal KDX for my weight and it always works out well for me. I'm 140lbs without gear and run .38 up front and 4.8 rear.
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Re: Front Spring Rate Question

Post by stnd » 04:16 pm Sep 30 2020

Thanks for the suggestions, I did end up emailing Racetech today to ask about the same thing, and they told me to look up spring rates for the bike i'm riding and buy that spring rate for the forks I'm running. So looks like i am ok with .41.

Thanks again.

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Re: Front Spring Rate Question

Post by KDXGarage » 06:06 pm Sep 30 2020

0.41 is not right for you unless you are following the grandkids around.
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Re: Front Spring Rate Question

Post by SS109 » 08:29 pm Sep 30 2020

I agree with KDXgarage. That spring recommendation is way too light.

When I was younger, and was a bit more aggressive rider, I ran .41's on my KDX with KX125 forks. Also, my buddy runs .40's and he's 170 pounds and is the same speed (a mid pack B racer) like me.
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Re: Front Spring Rate Question

Post by stnd » 07:17 pm Oct 01 2020

Thanks, that's exactly what I've been reading on this site, but I got that answer from Racetech.

I am probably beginner more than novice, and this is my first dirt bike so I have no frame of reference on how front should feel. Feels nice to me because all I had before was stock KDX forks which felt squishy.


Modifiers: (2002 KDX220)
Riding Type: Trail (single track)
Skill Level: Novice/C Class
Stiffness Preference: Standard Stiffness
Age: 30-44 Years Old
Height: Standard Rider Height
Gas Tank: Standard Gas Tank
Lowering: Not Lowered
Rider Weight: 220

FRONT FORK SPRINGS
Recommended Front Spring Rate: 0.41 kg/mm (Use closest available)

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Re: Front Spring Rate Question

Post by KDXGarage » 10:23 pm Oct 01 2020

"The best you've ridden is the best you know."
- Paul Thede

Paul Thede is the founder and head of Race Tech. This is a situation in which his words apply well.

If those forks are not valved for your skill / terrain / weight, etc., then putting the correct springs in them is going to make it feel worse.

If you have stock MX valving, then you currently have a poor mismatch of wrong springs and wrong valving. Both are masking the other.

A fair amount of folks on here have two or three problems, not just one. Throwing the correct rate springs in there rips the Band-Aid off the other problem(s). :grin:

At the same time, I do actually see that many are not in a rush to throw hundreds of dollars into 20 year old forks on a xx year old dirt bike they just ride for fun. I apologize to everyone for seeming like I don't ever see it from that side. :mrgreen: If one is racing, then I am indeed saying to dump the money. :busted:
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Re: Front Spring Rate Question

Post by stnd » 11:32 am Oct 02 2020

Hey thanks for that. I agree. This was my first step to addressing both the issues (Spring rate, and valving). Right now i ride with the compression 16 clicks out.

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Re: Front Spring Rate Question

Post by rungrandpa » 11:25 pm Oct 05 2020

Perfect spring rate for me for fast desert is .46. Perfect for hopping around on tricky trails is .42 I leave them at .44.
Everything is a compromise it seems.

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Re: Front Spring Rate Question

Post by Goofaroo » 09:24 am Nov 22 2020

What is it that you don’t like about the forks that you have now? Did you try servicing the stock forks before you bolted a motocross fork onto your off road bike?

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