Any Suspension Gurus That Can Help?

PTshox wrote:

I ve had good luck with RT's spring calculator and found it to be worth consulting. I use it as a base line. And if the...

I ve had good luck with RT's spring calculator and found it to be worth consulting. I use it as a base line. And if the fork feels too stiff it probably is. I put a 42KG spring in the front of my KTM 350 XCF (16 model yr) and stock is 45. 42 was much better. I put a 41kg spring in my YZ250FX (20 model year) and it was much better .. stock being 47.

I want my suspension to absorb stuff... not deflect off stuff!

Gary Duck wrote:

There a few things in the RMZ fork that needs to be addressed but since you want to keep the valving stock you can work on...

There a few things in the RMZ fork that needs to be addressed but since you want to keep the valving stock you can work on oil volume and spring preload. Like others have said the oil volume it to high in those forks stock but what nobody has mentioned is that the KYB forks have been coming with too much preload the last few years.

Pull your springs and measure them, you will likely find they measure in the 500-502mm range. That will set your preload in the 10-12mm range wich is too much for a fork spring. Funny thing is the actual KYB spec is 497mm but KYB doesn't seem to be able to produce their springs to their own specs lately. A 497mm spring will usually fall in the 7mm+/- range and I do like to see forks between 6-8mm.


Also note that if you look up your spec at Race Tech the spring they will sell you is 492mm. I assume they also identified the problem with the stock spring lengths and since they recommend 4mm preload, which I think is a little low, they are producing a shorter spring and supplying spacers to add up to the exact preload you want. The only problem with RT's approach is they sell to a lot of DIY people that don't understand suspension or read the tiny little note in the bottom of the box that says the springs may be shorter than stock and I see a lot of people throw them in with out the spacers assuming they are the same as stock and end up with almost no preload on the springs which is a bad thing too.

Gary Duck wrote:

People get spring rate numbers confused all the time because there in no consistant unit of measurement used in the industry. The stock fork spring is...

People get spring rate numbers confused all the time because there in no consistant unit of measurement used in the industry. The stock fork spring is .51kg but is advertised in the manual by newtons as 5.0N/mm.

If your guy has a set of 4.6 springs that would be newtons and are equal to .47kg. I think that may be a bit soft on the rate for you but it's worth a try if it doesn't cost you anything. If they are KYB take offs then they may be 500+mm and the extra preload and high oil volume may make them feel good. I'd prefer to use .49kg set at 6mm and 320-325cc of oil but there's always more than one way to skin a cat which is why you'll get different answers when you call different tuners. Ultimately the rider had to decide what feels best to them.

Sandusky26 wrote:

I want to know how the springs turned out