Preload question for Fredette Fork Springs

[K220]

I just completed installation of the 38kg springs that I had purchased from Fredette Racing. Based upon the many threads I have read in this forum, 10mm seems to the going "preload" setting, so I followed suite. After all was completed , I removed the bike from the stand and sat upon it, there was a significiant amount of "sag" difference between the stockers and the replacements. When I state significiant, I mean the bellows folded up quite abit. Did not take for a test ride, just sat upon it and "bounced" around and the front end seems extemely "soft". Has anyone else recently performed the above and ended up with the initial response?
Not to leave any details out, I did change the fluid out completely (turning forks upside down, ,moving fork rod in & outwards many times). Replaced fluid as per the service manual instructions, 100 mm from the top. As I was in no hurry and being my first at this, I took lots of time and double checked myself throughout the entire process.

Fredette did include some intructions that stated to set the preload same as "stock" springs. But all I have read states the stockers have too much preload, so I opted for the 10mm. Is this were I have errored ?

I did note during the process of measuring for the correct preload that there was 4mm lenght difference in the new springs. Therfore I cut each spacer accordingly. Is this common.

Thanks in advance for your opinions.

 

[K220]

No takers ??

Common guys, someone has crossed this bridge before. Through me a bone here !!!!!!!!

What is most confusing is the instructions supplied by Fredette stated to set preload same as "stock".. If that be the case, why include the PVC pipe ? Why not just reinstall the stock spacers ? I measured the stock spring and the Fredrette's ,,less than 4mm difference. Is 4mm so cruical that you need to custom cut a spacer? I probably spent a couple of hours last nite performing thread searchs and read many statments, that only confused me more. I emailed Fredette , (no response) and have tried calling several times this am (no answer). This is a do-it-your-self project going sour. As mentioned earlier, with the .38 installed with a 10mm preload spacer ,when I sit on the bike, quite abit of sag develops. (I weigh aprox 165lbs). I can near bottom the front iend out just rocking the bike forward. Something does not seem quite right with this picture.

 

[kmccune]

Common guys, someone has crossed this bridge before. Through me a bone here !!!!!!!!

As mentioned earlier, with the .38 installed with a 10mm preload spacer ,when I sit on the bike, quite abit of sag develops. (I weigh aprox 165lbs). QUOTE]

You need to cut the spacer to give you 10mm of preload, not put in a 10mm spacer.

 

[G. Gearloose]

Just how long is your current spacer, stem to stern?

What is your static sag? Now what is the sag with you on it?(laden)

Aim for 1-1.5" static, 2.5-2.75" when centered on the bike. Adjust the spacer accordingly to get these numbers. If the difference between the static and laden exceeds 1.75-2", your spings are too soft.

 

[Braahp]

Look at this chart. Shows the various force along the stroke of the forks. You'll see little difference with the stock springs and oem spacer vs. the .38 springs and 10mm of preload. Your stock springs were actually stiffer initially until forks were compressed more. Use the stock metal spacer. I couldn't get it to line up and space correctly posted here but you'll figure it out.

spring rate (kg/mm)
0.35 0.38 preload 20mm 10mm
- -
Force@ stroke (lb) stroke (mm)
38.6 33.5 30
54.0 50.3 50
65.6 62.8 65
77.2 75.4 80
88.7 88.0 95
100.3 100.5 110
111.9 113.1 125
123.5 125.7 140
135.0 138.2 155
146.6 150.8 170
158.2 163.4 185
169.8 175.9 200
181.3 188.5 215
192.9 201.1 230
204.5 213.6 245
216.0 226.2 260
227.6 238.8 275
239.2 251.3 290
250.8 263.9 305

 

[K220]

Although I worded it improperly, that is what I currently have (spacer cut to provide 10mm of preload). The spacers are are 71mm (not including the 2 washers).
At the moment I am in process of disassembly the forks again (thriple checking) and all measures up correctly. It's just the "feel" and "appearance" of the bike when sitting under it's own weight and/or mine. Noteable difference. Seems extremely "soft".
Maybe I am just paranoid. But the instructions from Fredette still have me in a puzzle "set preload according to stock" ???

 

[Twiztid One]

i just install my Fredette springs and i had the same question that you had , called jeff and he told me for my weight {185} to not use the supplied pvc and use the stock spacers . i also went with 7w oil a little heavier , took it out the other weekend and man what a difference it made .

 

[K220]

Braahp & Twinstid One

That was the repy I was hoping to receive to confirm my "red-neck" logic. The 38 springs are only aprox 3 mm longer then the OEMs, so why change the preload. I guess I spent to much time reading the treads and the muntiple opinions had me as mixed up as a can of worms.

Thanks for the input.

I have put off this project for several weeks. As I am off work this week and my 15 year old son is out of town with his Mom until tomorrow, I need to complete it and test run the results this pm. I was planning on making a road trip with son to ride for a few days while he and I are both off together. (Just haven't decided where as of yet) We just got into dirtbiking late last year. Best "bonding" time we have ever had next to ATVs. My son shakes his head in awe as I place order after order for "goodies" for our bikes and/or ourselves. I keep telling him I am spending his inheritance.

 

[Twiztid One]

i just bought my boy a little pw50 and hes got more gear than i do and i have been riding for 20 years , the best time is teaching him the ropes and to see him keeping up with me .

 

[kmccune]

:thumb:

 

[farcry2]

I installed 99 xr 400 springs in my 00 kdx, got on E-bay. It's strange but they were the same exact length as the kdx springs. I had also run into this with Fredette when I bought .42 kg/mm springs for my nephew, same length spring as stockers. Are the 99 stock xr springs the same length as kdx stockers?

On my 00 setup I cut the PVC down to give me 15mm less preload than the stock spacer or about 5mm if I measured correctly. I drained the stock oil and installed 5w maxima 110mm from top of collapsed fork with spring removed. My initial impression was that I screwed up the front end as it sagged when I took it off the stand. I took a test ride anyway. The forks were more plush, but I felt an imbalance between the front and rear suspesnion, the rear dominated the front. I reduced compression damping on the rear and backed off the shock preload 10mm and that seemed to help balance things out. I have a jump in my back yard that can bottom the stock fork setup pretty easy, and the new fork setup resisted bottoming. I have a ripped fork boot, so when I go to replace it I'll try the stock pre-load again to see which suits me better. I'll post again when I've done it.

 

[K220]

I reinstalled the original "steel pipe" spacers. Afterwards dropped the bike onto the garage floor, did appears the front end "settled" down abit more than with the original springs in, but no where near the point as when I had the 10mm preload set-up. After mounting Bike felt "right". Only had an opportunity to test around the yard. Frt end has a different feel. While I was at it I adjusted the "clickers" out to 12. They were set at "1" click out !! No wonder my arms were getting shorter each time I rode.
Thanks for the feed back guys !!! Things are looking up for my son and I to get in several days of back to back riding for the next few days.
Has anyone been riding at Durhampton Plantation in Georgia ? Got a few days in a row open and looking for a little adventure for son & I.

 

[Twiztid One]

hope all goes well and you like the new springs , give us a ride report after you give er a test . :)

 

[canyncarvr]

re: Is this common? (different length springs)

More common than it should be. This is the big deal: Do the springs CHANGE in length between maintenance? If so, you have some junk springs.

Seeing as these springs likely came out of some bin-full-o-springs, I'd expect the pair I bought to at least be the same length.

What does that tell you about the mfg's quality control?

Yes. Cutting the spacers individually to result in the same preload for each spring is the correct way to do it....NOT to cut the spacers the same.

re: steel spacers.

Why not save some money, put in a automotive valve spring (maybe 3.5" long) and a spacer nineteen inches long?

Isn't the point of the fork tube to hold a spring?

Seems reasonable to me.

 

[frdsrck]

Ah-ha - this is the thread I have been looking for! I have just bought new .38 Spring as well from FRP, and I am planning on doing the swap soon. So to clarify these threads.... I should keep it simple and "just use the stock spacers, and set up for stock pre-load" Correct? No need for the PVC spacers?

 

[Braahp]

Yeah I say keep it simple. I use the stock spacers and love it. Later on you might feel froggy and use the pvc and make spacers. But I say you'll like the stock metal with the .38 springs.

 

[tominator]

I ran into the same problem. I spoke to JF several times because the front end was too mushy when aiming for 10mm of preload. I also spoke to Mr. RaceTech. They don't see the world the same way. Jeff recommended using the stock preload spacers. This is about 30 mm of preload on my bike with FRP springs. It didn't work too good. The RaceTech website has a dirt bike suspension FAQ section that provides a table with recommended static sag ranges. On the front they recommend 65-75 mm. If you use this as a target and select say, 70 mm, it will get you close to where JF is talking about being.

The preload is going to be higher than you may expect. Mine is about 18 mm. I screwed aroung with this about 2 months. I ride some MX and some tight rooty rutted gully trails. It has worked-out a lot better than I thought that it would (BTW, I used RT oil level recommendation and JF shim recommendation).

In fact, the tuning recommendations that JF gave me for fast vs slow terrain are spot on. A lot of people say that my springs are too soft (0.40 for 190# rider per JF). I run my clickers from 6 (MX) to 16 (gully wash trails). My arms are never beat up. (I wish I could say that about my ass on the MX track. I guess I need to work on my shock some.) I fact, everyone that rides my bike says it's comfortable and controlable.

I thought about getting 0.44 springs, but I rarely bottom on the track and it is comfortable so I didn't. There are some good engineering reasons why RaceTech recommends heavier srings. However, there is a lot to be said for experience in tuning the KDX.

I can run wide open up a root filled gully in 3rd and steer the bike. I can also come up 3 feet short on a 30 ft table top (normal for me) at the track and not bite the cross bar.

I hope that this helps.

Tom

 

[Jackpiner57]

I installed the Fredette .42kg springs. I weigh 210 nekkid.
The new springs were longer than the stock, so I just cut the stock metal spacers shorter.

Example:

1. Left side spring 3/4" longer than stock, cut 3/4" off steel spacer etc.

These springs have softened up quite a bit in the last year. I think I need to get even stiffer springs. (or maybe I need to lose 25+ lbs.) Or maybe add a little more oil.(or maybe lose that 25+ lbs.) I'm confused. Please pass the sausages.

 

[G. Gearloose]

The RaceTech website has a dirt bike suspension FAQ section that provides a table with recommended static sag ranges. On the front they recommend 65-75 mm. If you use this as a target and select say, 70 mm, it will get you close to where JF is talking about being.

Well, static sag is when your not on the bike, so it better not be 3" (75mm). It should a little less than half that.... 25-35mm

Laden sag should be in the 65-75 mm range, and that is your target that determines initial preload, because that is where you want the forks to run to keep them on the dirt.

If you adjust the spacers to correct layden sag, but then static sag is much too small, then you need HIGHER rate spings, and thus the converse.

 

[tominator]

From the RaceTech FAQ I mentioned:

Q: What is "Race Sag" (Static Sag)?
A: Static Sag or Race Sag is the amount the bike compresses from fully extended, with the rider on board.

 

[canyncarvr]

Not the first time RaceTech has been wrong.

I didn't check the quote...but 'Race Sag' and 'Static Sag' are NOT the same thing.

Gearloose is correct. RaceTech (given a correct rendition of their FAQ) is wrong.

Besides...HE approved his message!! It's gotta be right! ;)

**edit**
OK...I went and read it. They're still wrong. You might consider it a matter of semantics, but words DO mean things...and the way they use the term 'static sag' and relate it to being measured with a rider on-board is different from the way anyone else in the business describes it. Well, the sites that refer to RaceTech's site have it wrong the same way!

Their term 'free sag' is static sag. Their term 'static sag' is race sag.

Like:
this.

this.

this.

this.

this.

..to list a few out of several thousand

 

[G. Gearloose]

Thanks CC, I was starting to question my sanity...with poor results.

No wonder so many have trouble with the preload thang, if a big player like racetech can't get the terminology accurate.