Quote:
Originally Posted by ieathonda
So the forks I am getting will be the pregen Ex500. Since the springs are longer, what is the approximate spacer size so sag is set correctly? And since the ex500 spring is longer, wouldn't fitting it into the 250 essentially increase the effective spring rate since it would be compressed to the size of the 250 spring? Would the spacer be smaller to accommodate this longer spring?
|
The spring's rate is set by its length and how it's made. Compressing it more or less doesn't change the spring's rate at all. If the fork was exactly the length of the OEM spring, and you replaced it with a longer spring, it would inherently be preloaded some. But as stated above, preload does not affect the spring's rate, only how it behaves within its range of travel.
Generally speaking, you want the new spring & spacer to be the same length as the old spring & spacer. So if the new spring is 2" longer, you'd want to make the new spacer 2" shorter to compensate for that.
However, changing the spring rate inherently changes the length of spacer needed to maintain the same amount of preload. If your spacer is compressing your .44kg/mm spring down 10mm, that's 4.4kg of preload. 4.4kg of preload on a .585kg/mm spring only requires the spacer to compress it by 7.5mm.
But if you don't currently have the spacer length set to give you proper preload/sag, then trying to get the new parts to match the current (incorrect) settings is pointless.
http://www.ex-500.com/wiki/index.php...ension_Preload has a lot of info to help you understand preload/sag, and how to properly set it. This is where preload adjusters would come in handy, as you can simply turn them up or down instead of tweaking the length of your spacer. But once you get them set, you don't really change them much (perhaps between street and track riding, or between a really rough track and a really smooth track).
As Ghostt said above, the Gen1 springs should be the same .585kg/mm rate as the Gen2 springs, just longer. This gives you a little room to play with the rate if you want. Think of a spring as a long, coiled lever. Making it shorter makes it harder to bend; cutting a spring shorter will actually increase its rate. Based on Ghostt's pic above, it looks like the 500 spring is 20-3/8". You can find a new length or rate with the formula
Length1 * Rate1 = Length2 * Rate2. 20.375*.585 is 11.919375, so divide that number by a desired length or rate to find the corresponding rate or length. Cutting it down to an even 19" would give you a .627kg/mm rate, for example. That might be an easy way to bump the spring up a little closer to what it "should be" for your weight.