I'm trying to figure out the correct spring rates for my son's KX250F.

I've checked out the Race-Tech spring rate calculator, as well as the on on MX-Tech's website and they both come up with different spring rates. With Race-Tech's calcs, I can stick with the stock rear (5.0) and just throw some softer fork springs in (.42). According to MX-Tech's calculator, I should go with even softer fork springs (.40) and a softer shock spring (4.8).

Does anybody know of another calculator so I could go best 2 of 3, or know if of the two calculators tends to be more accurate?

Thanks for any help.

deano...

What is your sons weight and what sort of riding is he doing? MXtech sometimes goes softer on the rear, but their rate is gear on, Race Tech's is gear off. Both can be out at times. But they give you a ball park, but your also wise to ask others for help. There is no other calculator that I'm aware off.

My son run's about 145 with gear on and we ride so-cal desert mostly. The soils here cover everything from soft sand, to rocks to hardpack. Mostly need something that can handle the long trails of whoops.

Given that he's growing quickly, I think we'll just stay with the stock shock spring and go with the Race Tech recommended fork springs. While it might run on the slightly stiff side for now, at least he won't be out growing them next week.

Say Deano: Forget the calculators, although they will get you/him in the ballpark; it's best to check static and race sag numbers with springs that are close and use the one which fits the target range.

I've got a 4.9 and 5.2 you can experiment with and have; drop me a line. These would be good for him as he grows and increases in confidence/speed.