KYB USD Shim Stack Theory

[KDXGarage]

Hey, look! He has tore into his forks. Way to go. It is the only way you will know for sure what is going on in there, (says I).

Any chance they are .15mm or .2mm instead of .18mm? .15mm is .0059 inches. .20mm is .0079 inches.

On #8 and #9, you are saying that the ring thickness is 1.5mm, right? 8mm ID plus 1.5mm plus 1.5mm = 11mm, right? I took apart one of my fork stacks this morning, and it was similar. 6mm ID with 9mm OD (TEEEEENY TINY!).

[canyncarvr]

Chances of that are most excellent, I'm sure. I didn't do any interpolation. Am using a simple caliper..not a SEM.

.5 of .001 isn't a whole lot diff in horseshoes (or anyplace else). It makes a big diff in the magical world of shims.

Just looked at it again. Zeroed my caliper good. Squeezed the shim good IN the caliper (a little springy). Looks a lot closer to .006" than .007". Call it a .15mm shim.

re: 8&9. Yup. Teeeeeny tiny indeed.

Hate to disillusion you...but I could tear into those things all day long...and STILL not know even for a guess what's going on in there!

It's all FM to me!

[KDXGarage]

On the Race Tech Gold Valve installation video, Paul Thede mentions that a Gold Valve kit only comes with .1mm and .15mm shims. I just used a calculator to figure out how thick .1mm and .15mm were in inches. I then measured the shims, and whichever one it was closer to, is which one it is. They were dang close to .0039" and .0059".

What's a "SEM"?

I have looked on RT, MX Tech, Suspension Network and various other internet discussion areas and never heard of a .18. I am not saying it doesn't exist! I was just asking. I know my '87 shock had some .125mm compression shims, as best I measured. Most CR, KX, RM, YZ, XR, etc. stacks I have seen are .1, .15, .2 and other seemingly common numbers.

It sounds like you are delving into a complex fork. I am glad I am working my way up slowly. I need to figure out KDX forks kirst.

What's "FM to me" mean?

[Indawoods]

CC
Sounds like a Dual Stage setup... is that right? Are you gonna try it first? How'd the oil look? sounds a lot softer than the stock stack... Kinda nice to know that someone has taken the time to adjust the suspension..... Don't forget to put the current shim stack in your bike profile in the new forum named as such.
http://kdx.woodsrider.net/viewforum.php?f=103
You can change the profile as it changes...

[canyncarvr]

There is only a single 'tapered' stack as I see it. The two much thicker shims on the bottom perform some other purpose than being part of the flexing stack assy.

Oil? That was kind of funny. Where the internal parts met in the fork..like the cartridge and the fork tube..there was a good deal of the gray goop you see in forks that haven't been serviced in awhile.

But the oil itself was red enough to look like it just came out of a bottle.

Now that I know the stack is indeed considerably different from OEM, I'll try it out.

...still no wheel.

[canyncarvr]

Got a wheel!!!

And it's been here for over a WEEK! Someone moved it from in front of the shop door..down the hallway through another passage door. Not someplace I wander around. Besides, wouldn't you think the UPS guy would leave a doorknocker?

I asked the shipper about six times for a tracking number. Didn't get one. Cripes!! I've been dinging on him for days...'Where is it??' No answer...

Looks like a new rotor on it. Not even any pad marks! Of course...every spoke is loose..but a quick look doesn't tell me the hub is beat to hell.

I have no understanding how a rider can take such pi$$-poor care of his equipment.

Now...I'm looking for a KDX stem so I can keep my KDX stuff intact...and I'm ready to get this done!!!

[Indawoods]

Damn CC... I just seen one on eBay... may still be there!

[canyncarvr]

I just looked. I get nothing.

Oh..gotta pick up an axle, spacers and misc fork guard hardware, too...

[T-Roy]

Carvr, what year is your forks and wheel?

[canyncarvr]

Forks are said to be off a '99. Wheel the same (they said).

I had hoped the axle came with the forks. It was in the pic, anyway. But...nope. It was some CR axle they used to hold the forks up so they could take the pic!

Did see an '89 KDX stem on ebay. Not the same PN according to BuyKawi, though. Maybe the stem itself is the same...who knows? Not me!

[T-Roy]

I believe you can get an oem axle for around $35.

Did you try FRP for the stem? Maybe Ski can have a few made up for us... I don't personally know any machinest.

[canyncarvr]

Yep. I've priced the axle..and that's about right. Add in the dust seals, spacers nut, etc etc..it adds up.

I'll keep looking for awhile.

Haven't asked Fredette about a stem. I'll do that.


Thanks!

[KDXGarage]

I am glad to hear you got your wheel!

I have a 1990 KDX200 lower triple clamp out in the garage if you want pictures. I have also got a 1987 lower triple clamp if you want pictures of that, too. I can take some measurements, too. I have a 6" caliper, but only a 0" - 1" micrometer.

I know one difference in the 1989 - 1992 KDX200 lower triple clamp and '95 and newer triple clamps that is throwing the part number off. That is the headlight mounting method.

[Indawoods]

Here ya be CC!!!!

http://cgi.ebay.com/ebaymotors/ws/eBayI ... gory=34284

[canyncarvr]

Thanks for the tip!

BTW...FRP has 'them', too. Now, I told FRP I was looking for a stem, didn't care if it had a clamp on it or not. He said, he had 'them'. I don't know if that means 'stem' or 'clamp'.

Thanks, TRoy for that. It hadn't occurred to me to ask FRP!

Anyway...he has the piece for $50. So...if the ebay thing doesn't work out, I know where to get one!

Which (sez me) is the clear way to go as opposed to ruining my KDX clamp. This way (buying an 'extra' stem) I can change BACK to my oem forks for whatever reason.

Anyway...thanks, folks (Jason did too!) for watching out for the part!

I appreciate it!!

[skipro3]

Now...I'm looking for a KDX stem so I can keep my KDX stuff intact...and I'm ready to get this done!!!

Chicken!!! Cluck, cluck, cluck.
Just go for it man! The stem or clamp aren't ruined if you have them pressed off. It is reversable. Well, as long as you don't use the Trev method and explode a grinder wheel into your face.

I can't wait for your opinion on the fork setup. Remeber, ride that thing hard....hit things hard with it and see how it performs. That's where the KX boingers really shine.

[skipro3]

Hey CC, Did you read all of the "shim basics" lessons? There are 9 of them on that site. It really explained what the stack is doing as well as explaining the dual vs. single stack. And then the photos!!! Wow! That really explained how a shim works as a flat spring against the oil coming out the port in the valve.

Without the tutorial, the charts didn't make any sense to me. Now they do. Not that I could develop a stack, just that I can now read the chart and I know what a stack can do as well as what a valve can do.

Too much!!!!

[skipro3]

I have read, 'Inside diameter doesn't matter.' Really? Then why is it that people that know (like Jeremy from MX-Tech) do NOT use all the same inside diameter shims? Methinks there IS a reason they aren't the same...that it DOES matter.

Since flat disk springs become proportionally stiffer as the deflections increase, (non-linear) the larger inside diameter will affect the deflection curve. This nonlinear deflection-load curve plays an important part in making suspensions work the way they do. The larger the inner diameter, the steeper the curve (less spring surface to distribute the range over) The smaller the inner diameter, the longer the spring of an individual shim is and the curve is affected accordingly.

I think, in a nutshell, a larger inside diameter shim, AKA spring, acts like a shorter coil spring: it will "bottom out" sooner. It has less spring length than a smaller inside diameter shim. After all a shim is a flat spring.