KDXRIDER.NET

I was just trolling through KDXRider.net and saw something that concerns me...I read that the FRP fork springs are shorter than the stock ones, and then I saw a comment about adding preload via a PVC spacer (cut pipe) to make up the difference.

About a year ago, I installed FRP 0.40kg/mm springs in my stock forks (2003 KDX200) and I did NOT install any PVC spacer for additional preload.

Any chance I've buggered up my forks now? I plan to take them apart this weekend for an oil change. Any damage I should look for? Or should I just cut a small section of PVC pipe and add it while they are apart? How long should the cut pipe (preload spacer) be, and is this in addition to the metal spacer already in there?

If the springs were too short the front would have sagged way down and you would see that obviously. If the springs were too long there would be way too much pre-load and you wouldn't have much front static sag. I doubt anything bad happened or you would see or feel it. You might have too low of front end is the worst case with a poor handling suspension.

Re: '...I read that the FRP fork springs are shorter than the stock ones..'

That is not correct. They are the same length as the stock springs..around 470mm. They are shorter than other choices, like the Honda XR springs.

ALL springs vary, even for the same applications. Springs are made with a tension, thickness, coil spec, and if those are all 'the same' then the length will be 'the same'.

But those specs are NOT always the same.

The point is a RATE, not a LENGTH.

Re: 'and I did NOT install any PVC spacer for additional preload. '

But...you DID use the metal spacers? You're saying you did not ADD more? Well, that is what you said, but is it what you meant? IF you did (add), then you have way too much preload anyway.

IF you used JUST the metal spacers, you have way too much preload anyway.

Consider: The OEM preload is something like 35mm. That is the amount the spring is COMPRESSED just sitting there on the rod, before the fork is even on the bike.

THAT is too much. Well, too much for a correct rate spring. The OEM spring is 'correct' for about nobody, so a 35mm preload spec is a moot point.

If .40s are correct for you, I suggest preloading the fork springs to no greater than 10mm. I also suggest you experiment with different preloads.

A preload change in my OEM forks from 8mm to 3mm made a significant difference in the front end tracking ability. 'Significant' meaning from a NON-compliant, pain in the rear, can't track out of any rut to a suspension that actually worked like it was supposed to.

Why? Because the KDX forks have no rebound control (other than from oil viscosity). Too much pressure forcing the forks apart is NOT at all a good thing.

I'm saying it's a BAD thing!

Good info guys, thanks a lot!

I am currently using the stock metal spacers with no additional preload. Since I'm taking the forks apart for an oil change anyway, this is a good time to experiment with other preload values (1" PVC, right?).

I don't know how precise I can be with a ruler and a hacksaw, but I'll give it a shot. Surely I can get it down from 35mm...

Maybe once that is done I can troll eBay for some KX forks...

Thanks again!

Yes, 1" SCHEDULE 40 PVC. The thick(er) stuff. You can get a piece of it from probably any hardware store for probably a $.

Re: Precise

You can use a miterbox, compound saw or a table saw, too.

If a hacksaw is your choice, use something as a guide to back the hacksaw blade (if you cut with a hacksaw anywhere as close to as well as I do), like a second piece of that PVC you're cutting.