Posts
4
Joined
9/11/2020
Location
Queenstown, NZ
Hi all,
I’ve just purchased a new generation very slightly used XACT pro 7548 cone valve fork, I’m intending on sending this fork away to Kreft moto eventually to get set up for me personally but I thought I’d start with the correct spring rate first and go from there! previous owner had this on their 2019 KTM 450SXF they weighed around 86kg/190lbs and have 4.8nm/0.49kg fork springs installed. Forks are now going on a 2020 KTM 250SXF I weigh 77kg/170lbs with no gear and consider myself an intermediate rider who rides a mix of moto and cross country style racing. The race tech calculator recommends a 4.4nm/0.45kg springs but that seems a bit light don’t you think? Do you guys think a 4.6nm/0.47kg rate is more suitable?
Thanks in advance!
I’ve just purchased a new generation very slightly used XACT pro 7548 cone valve fork, I’m intending on sending this fork away to Kreft moto eventually to get set up for me personally but I thought I’d start with the correct spring rate first and go from there! previous owner had this on their 2019 KTM 450SXF they weighed around 86kg/190lbs and have 4.8nm/0.49kg fork springs installed. Forks are now going on a 2020 KTM 250SXF I weigh 77kg/170lbs with no gear and consider myself an intermediate rider who rides a mix of moto and cross country style racing. The race tech calculator recommends a 4.4nm/0.45kg springs but that seems a bit light don’t you think? Do you guys think a 4.6nm/0.47kg rate is more suitable?
Thanks in advance!
Id start at 46 for you then you can add a turn or 2 or preload. if it feels too soft, try the 47 with no preload and soften the compression. It really will depend on the type of dirt and tracks you ride. I have my bike set up for Hard dirt, rough tracks.
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I've also never had a fork with adjustable preload so realistically if the spring rate is on the light end for me how far can you go in on the preload on these forks and will that change just the initial height/feel of the fork or make it stiffer throughout?
Thanks again guys
Zero preload added by the outside adjusters, as I like to use the spring's full travel.
What do you currently have the sag at, and how much preload on the spring to achieve that sag? That will give you some clues as to what direction to go.
But, at 160lbs, I think a 45NM shock spring is going to be too much for you. I think you're going to be better off going softer on the fork springs.
I’m 175lbs and run a .46 front spring and a 45 rear spring. I think your front is too stiff and the back is just right. Swap the front springs, set the forks to the second line and run the sag at 103mm.
Thanks, everyone.
Does anyone have a reference for a spring chart that shows dia and length by Cone Valve model or year?
My plan is to install a set of 0.46 (maybe a little softer) and tune from a known rate.
Usual story: bought a set of used CV forks and although I have the setup sheet, it's not always reliable, so it will be good to get a set of 0.46s in there.
You should send them to someone that has experience with cone valves to 1. Make sure you get the rate you need. 2. Make sure you have the right set of cones for what you’re riding and that it’s setup right (preload spring tension, oil level, ect.). 3. Replace the seals and bushings as needed.
Get a set of 4.4 try them, if you want to go 4.6 split it with a 4.8 (which you have already have). So in reality you have 3 spring rates available to try.
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