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Correct Factory Spring Rates #144922 04/15/19 09:01 PM
Joined: Sep 2018
Posts: 27
Detour Offline OP
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I am trying to figure out what the factory fork spring rates are.

My Yamaha service manual says
XT225 (K1) = .35 kg/mm (K2) = .40 kg/mm (I have no idea what K1 and K2 means)
TTR225 (K1) = .69 kg/mm (K2) = .78 kg/mm

RaceTech website shows
XT225 .23 kg/mm stock
TTR225 .38 kg/mm stock
.45 kg/mm is recommended for my weight

So does anyone know which is accurate? I am looking at swapping the TTR225 springs into my XT forks.


An O2 dependent, H2O saturated, carbon based life-form that swims slower than a sea-cucumber.
Re: Correct Factory Spring Rates [Re: Detour] #144942 04/17/19 02:10 PM
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peejman Offline
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K1 and K2 refer to spring rates... perhaps its a progressive spring that changes rate at some point in the travel. I don't really know.

You have to be careful swapping springs. Sometime there's different length spacers to change the travel or prevent the spring from being compressed too far and breaking.

You can search this thread for fork springs, plenty of people have made upgrades. https://advrider.com/f/threads/the-official-xt225-thread.178968/

Last edited by peejman; 04/17/19 02:10 PM.

This shall pass, be still and know.
2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.
Re: Correct Factory Spring Rates [Re: Detour] #145093 04/26/19 02:18 PM
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Detour Offline OP
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Ok, the K1/K2 part makes sense that it would be for a progressive spring.

I will have to call Racetech and see if they know the source of their factory spring rates, because that is quite a bit of a difference vs the Yamaha factory service manual.

Swapping the TTR and XT springs shouldn't be a problem for travel as you described since they are the same fork. However, I do know what you mean. I have swapped springs in a few bikes over the years and spend a fair bit of time researching the spring rates and lengths so I have a rough idea on what is needed. (spacers, oil level, tire/fork clearance)


An O2 dependent, H2O saturated, carbon based life-form that swims slower than a sea-cucumber.

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