Forkspring spacer- Not sure what for

[RJ-KDX]

Forkspring spacer- or Preload

I just got my new forksprings from Fredette. Along with the springs was a piece of pvc pipe. I called Fredette to find out the use, and he is out of town till next week. The lady with whom I talked with said it was a spacer. OK, but where?

Looked on the parts page on KHI's website, it shows a spacer above the spring(KHI #92143-1645 Fork Collar L=90mm), the one with the washers on top and bottom. When I changed my fork oil the last time, I cleaned this off before re-assembly, and if memory serves me it was metal.

Are you supposed to change the length when you get new springs? Am I even on the right page? If anyone has done this or knows what I am talking about, any information will be greatly appreciated.

Thanks, RJ

p.s. I went to Just KDX and found the preload tip, no picture also. I measured my spring and it was 476.25mm(18.75") not quite 539mm like in the setup tip. Is this what the pvc is for?

 

[Zerotact]

You trim the piece of pvc and use it as a spacer to get the right pre-load. you use that instead of the metal spacer

 

[canyncarvr]

re: are you supposed to change..

Yes. The oem preload is probably incorrect for your situation. It's around 30-35mm!!

Your fork sag should be in the 40-50mm range. You can get that with an incorrect spring choice AND an incorrect preload spacer.

With the correct spring rate, the correct preload spacer will probably be quite a bit shorter.

...depends on the length of the spring, too...but that's kinda' another issue.

DO figure each spacer separately for each spring. It's not always true that a spring 'pair' is exactly the same length.

A search for <preload><spring><fork> in this board over the last year got me 16 threads.

Try it.
;)

 

[RJ-KDX]

Thanks CC for the reply. I dropped in "preload" into the search and found tons of stuff.

I was stringing too many words together before, so no returns.

CC, soooooo you think the 30 to 40mm of preload is a bit much. So if I take about 10 to 15mm OFF of the 90mm stock spacer, that should take me closer to the 10mm preload. You think?

Thanks again. :worship:

 

[canyncarvr]

It's not a matter of taking something off what was previously there. You're subtracting from an unknown quantity so you'll get an unknown result.

Figure it from the other direction.

From the top of the spring to the bottom of the cap (spring in the fork, fork collapsed, cap screwed on fully extended rod) measure X. Subtract the thickness of the two oem washers (3mm). Add to that figure the amount of preload you want to get the spacer length you need.

So, if X=60mm and you want 15mm of preload, your cut spacer length would be (60-3+15 72mm. **corrected**

The pvc you got from frp isn't anything special. If you goober it somehow you can pick up another piece of it from any store that deals with plumbing stuff.

 

[89kdx200rdr]

you can get 10 ft of it at home depot for $2.50

 

[RJ-KDX]

Originally posted by canyncarvr
From the top of the spring to the bottom of the cap (spring in the fork, fork collapsed, cap screwed on fully extended rod) measure X.

Aaaahhhh, now it all makes sense. :confused:

I was looking for a measurement of the spring set-up(all pieces included; a magic number like let's say 600mm(for example)) that you could use to figure the amount.

Sometimes we look too hard to find the simple things, ME included.

Different subject: In a search of "preload" I found some posts from you(CC) that stated you didn't like 470mm springs. What's that all about? You(CC) mentioned you liked honda 500mm+ springs. Just curious.

Thanks again. :thumb:

 

[canyncarvr]

Well...if you found those posts, you probably came across some of the reasons?

Basically, the point of the fork is suspension, isn't it? Then why fill it with almost 4" of steel (the oem spacer)?

A spring does not compress in a linear fashion. The more it is compressed, the faster the rate changes. A longer spring can be compressed further and retain its stated rate.

I've heard argument regarding motion transfer time..that a shorter spring transmits motion faster, and that speed is good. OK. The difference of that in the real world between a 470mm and a 530mm spring is likely zip.

I've heard the argument of weight difference, the spring being an unsprung component...and unsprung weight is a bad thing. I need to weigh an oem spring and compare it to one of my XR springs...but I'll bet it's next to nothing difference wise.

So, back to the world of real. I rode two kdxs modified exactly the same with the exception of one with XR springs, one with eibach (470mm) springs. Huge difference. Huge enough that from one ride to the next on my bike with the .40 eibach 470mm springs changed to the .40 honda 530mm springs, the difference was still huge. No question but that the longer spring performed better.

The fact that oem springs are generally hot-wound, and aftermarket springs are cold-wound is a plus. Failure rate of cold-wound springs isn't huge, but it happens. It happened to me, actually. A brand new set of .42s failed with one spring getting 10mm shorter than the other over the span of several rides.

That's BS.

There are reasons to use longer spacers. Where the fork rides in the stroke is important for proper suspension. That's where the sag measurement comes in. If you have to use 4" of spacer to get the sag in the ballpark, I'd say you need a different spring in the first place.

 

[JasonWho]

---

 

[RJ-KDX]

Originally posted by canyncarvr Then why fill it with almost 4" of steel (the oem spacer)?

After review and some thinking, I came up with this: I measured the new springs @ 469.9mm(18.5") close enough to call 470. I measured the old springs 1@ 469.9mm(18.5") and the other at 468.3mm(18.4375").

There was only a 1/16"(1.58mm) difference between the two stock springs. IMO close enough to call them the same.

OK, here goes, I measured the space from the top of the spring to under the shoulder on the cap(screwed all the way down, of course). The distance was 3.1875"(80.96mm). We'll call it 81mm for ease of discussion.

So, if X=60mm and you want 15mm of preload, your cut spacer length would be (60-3+15 69mm.

Now using the corrected formula (60-3+15=72) :eek: Just kidding.
No offence CC.

OK, focus, focus, where was I, Oh yeah, 81-3+15=93. Now with this number we go backwards(or just change a number) 81-3+12=90, this is the stock spacer length. So what this tells me is the stock springs have 12mm of preload. Do you agree?

Now another one is this, the service manual states the fork spring free length as 457.5mm(18.012"). This a diff of .488"(12.39mm). I don't know about your springs but I don't think they GROW over time.

Things that make you go :think: .

 

[canyncarvr]

'He's an idiot,' I said of myself.

That's kinda funny, cuz the math seemed obviously wrong...so I actually penciled it out..and got the same stoopid number.

Crap. I have no idea where the bogus number came from. Obviously no thinking was involved.

My apologies. :(

I'll give this another go......

I question the starting measurement. I can tell you that on my bike ('00 200) the measurement with the oem spring (470mm) is closer to 60mm.

Of course, considering the math above..you've GOT to question any measurement, 'eh?

I don't know what you could do to get the measurement so wide. You could compress the spring somehow...you could put the rod under tension (you don't yank on it.

How about this? Where is the jam nut when you measure the space? It must be well below the cap. It can't interfere in any way with the threading-on of the cap.

Something's wrong, I'd say. I don't think there is any difference in the forks in the 'H' models.

Hey..what does 'under the shoulder of the cap,' mean? You measure to the bottom of the cap..to where the spring seats. Certainly not to the 'shoulder' as I'd describe the piece of the cap that sits on top of the fork. The spring doesn't go anywheres close to that spot.

 

[RJ-KDX]

Originally posted by canyncarvr
'He's an idiot,' I said of myself.

That's kinda funny, cuz the math seemed obviously wrong...so I actually penciled it out..and got the same stoopid number.

Not a problem. ;) We're all semi friends, right?

Hey..what does 'under the shoulder of the cap,' mean? You measure to the bottom of the cap..to where the spring seats. Certainly not to the 'shoulder' as I'd describe the piece of the cap that sits on top of the fork. The spring doesn't go anywheres close to that spot.

As soon as I read this, I realized my error. "Under the shoulder of the cap" meant from where the top of the fork contacts the cap. I'm gonna make a guess that it's about 21mm(.827") for the difference. See CC, if you hadn't replied I wouldn't have found my error.

So with this info we can figure there is about 30mm of factory preload. I think you(CC) had already said this.

Thanks for all your help, CC! ;) :laugh: ;)

 

[RJ-KDX]

Just FYI, I cut new spacers for 15mm of preload, set my clickers to 11, and put everything back together and went riding on Sat. They felt great. After hitting the water breaks/jumps all day on the trails, I think I can go maybe two clicks harder without a problem.

Thanks to CC for helping me see the light. :thumb: :aj: :laugh:

 

[canyncarvr]

Any time.

A quick refresher of good 'help': 60-3+15 = 69mm

Oh yeah! There's some help for 'ya!! ;)

Good to hear the result is satisfactory!

BTW...there's more to the clickers (compression) on the forks than how the forks respond to large impacts (water bars and jumps). If you find the front end tracking poorly on downhills...say, wanting to stay in small ruts instead of allowing you to turn out of them (it'll want to tuck under), or the same thing on uphills...not being able to easily manuever out of a rut cuz the front end skips on a rut edge instead of climbing out of it; those two situations are indicative of too many clicks on the forks. Maybe too much preload, too.

Cheers!

 

[RJ-KDX]

Originally posted by canyncarvr
Any time.

A quick refresher of good 'help': 60-3+15 = 69mm

Oh yeah! There's some help for 'ya!! ;)

ROTFLMAO !!! :laugh: :laugh: