Question about correct sprig rates for my weight...

YO!!! Im on a 2009 RMZ 450 and I'm too heavy for the stock springs. I used RaceTech's calculator and they recomend a rate that they dont offer, see below:


Recommended Fork Spring Rate: 0.505 kg/mm (use closest available)

Stock Fork Spring Rate: 0.47 kg/mm(stock)

Available FRSP 4349 Series Springs are:

-RT FRK SPR 42.7x493mm .49kg FRSP 434949 $114.99

-RT FRK SPR 42.7x493mm .52kg FRSP 434952 $114.99

The closest size availible is stiffer than recomended. In a situation like this, is it better to go a bit stiffer? The rear is not as close as the front recomendation.


Recommended Shock Spring Rate: 5.92 kg/mm (use closest available)

Stock Shock Spring Rate: 5.5 kg/mm (stock)

Available SRSP 6727 Series Springs are:

-RT SHK SPR 66.9x64x267 5.7kg SRSP 672757 $114.99

-RT SHK SPR 66.9x64x267 6.0kg SRSP 672760 $114.99

What do you guys think?? Thanx for the help!!:smirk:

Edited by moto_xmayhem21

what do you weigh?

-222 lbs. Also, this is a track only bike. No trails whatsoever.

Just re-read my first post, and all the "u's" were missing! Haha, the "u" key got stuck!

defiantly 0.49 and 6.0 IMO

Ok, I understand that the slight difference between the rates may be trivial, but would you mind elaborating on your recomendation?

I personally like the front end not to beat the crap out of me through the choppy stuff. I understand that is more valving than spring, and that i can adjust oil height. But in the front you recomend thed lighter of the two choices, and in the rear you would chose the stiffer of the two.

My best guess is that those choices are just the CLOSEST to what RaceTech offers????

What are your thoughts there? Thanx for your replys as well!!

I have charts that I trust , it says 0.49 and that makes me think the 0.52 will be too stiff, it doesn't seem to go as a 1-1 ratio compared to the rear like sone charts say , on the rear it says 5.8 to 6.1 and you are in the middle weight wise of those 2 rates so the 6.0 is the closest , also stiff shock springs don't seem to hurt in terms of harsh feel like a stiff fork spring does

Ok, so I was sort of on track with your trainof thought. Awesome bro, thank you for your input! Now I just have to come up with the $$$$$$! Is the spring swap as easy as the older suspensions, like a 2002 set of KYB's? Thats the earliest pair of forks ive ever cracked open and I know thats an easy spring swap. THANX!!!!

the shock you have to uncover the circlip on the bottom spring mount , is actually easier if it's not all corroded , the forks are different but not harder , do a search on spring change videos as there are lots of links and it shows you step by step , also dsp springs on eBay are much cheaper and just as good

I could not find any on ebay or amazon, but I know they come and go. I also have the owners manual so I guess I can stop asking stupid questions! Ha!

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