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Race Tech Spring Calculator

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OK I'm sure you have seen or used the spring rate calculator at racetech.com.

This is a great tool they provide for the OCD MX guy. I have been looking at it trying to figure out what fork spring rate is the most correct choice for me. But I realized something odd. :banghead:

If I look at both the fork and shock springs and keep changing the weights until the calculator specs the OEM spring rate I come up with significant weight spread. In otherwords the way the bike is set up from the factory is unbalanced between front/rear. :banghead:🤣

The OEM fork spring rate is .470, according to the calculator this is good for a 220# rider.

The OEM shock spring is a 5.0 and according to the calculator this is only good for a 185#

I have not called Race Tech yet but I just wanted to know what you guys think.

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The rear shock is probably set up a little stiffer, while the fork valving may be set a tad softer..

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The 450X rear shock spring specs out to a 5.4 with a slight progression starting out at 5.3kg/mm. We ran this on our Rhoerig engineering dynamic spring rater that produces a dynamic graph across the entire usable travel of the spring, not just one point.

Even with a 5.4, the bike is still unbalanced. You need atleast a 5.8 on this heavy bike to match the front end.

Take Care, John

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The rear shock is probably set up a little stiffer, while the fork valving may be set a tad softer..

OK I could buy that, but than how do you know what spring rates are really needed when you don't know or reference the valving?

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The 450X rear shock spring specs out to a 5.4 with a slight progression starting out at 5.3kg/mm. We ran this on our Rhoerig engineering dynamic spring rater that produces a dynamic graph across the entire usable travel of the spring, not just one point.

Even with a 5.4, the bike is still unbalanced. You need atleast a 5.8 on this heavy bike to match the front end.

Take Care, John

John, why would Honda sell a bike with unmatched suspension? :banghead:

EDITED: I just looked at my CRF Manuel and it states that the OEM front spring rate is good for a rider between 150-160#. This further confuses me as it further conflicts with what RT calculator says as well as others.

I have the need for lighter than stock rates either way as I weigh 140#.

I have reduced the rear to a 5.0 and use most all of the fork travel but want to try a softer fork spring rate to help better balance the bike. If really needed? :banghead:

My main dilemma is that

a) I don't want to do something I really wont get a benefit from.

🤣 I don't want to keep wasting money swapping springs out?

c) I don't want to keep disassembling my forks, wasting time and oil.

I have been told to try the CRF / CR 250 fork springs witch are .42 and if I am near the last 1" of fork travel on springs rated for a 220# rider with me @ 140#, I am lead to believe that going all the way to a .42 will cause the forks to bottom all the time. My instinstint is to lean toward a .45 or do nothing at all. 🤣

Whats your take, and where is the beat compromise. Better balance F/R or not to have the forks bottom?

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I am not a suspension pro, so I just went with the suggested rates for my 04 WR 450.

I spent some time getting the sag, compression, and rebound right, but in the end, the rates were perfect from the calculator.

I ride mostly woods and use the entire travel when riding aggressively.

This may be off topic, but IMO trust the calculator. :banghead:

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