Stem sizes.

jafo · Post by **jafo** » 05:24 pm May 25 2005

Theres been much talk about knurling and not knurling for the stem swap on this conversion. I myself have measured the stem holes in both clamps and they are the same size hole, at least between the '97 KX 250 clamp and my 2003 KDX clamp. The only real differences I can see are the stem thickness and diameter, bearing and race size on the top bearing. I kind of wonder if just a race and bearing swap might do the trick instead of swaping the stems. It also got me to thinking, that maybe the years of bikes invovled has alot to do with this deal of whether your required to knurl the stem or not. My KDX is a 2003 model. The forks I'm using are off a '97 KX 250 model. I'm thinking maybe theres some size difference in the stems between years of KDX bikes. I have'nt seen any measurements from the other swaps in the club, or I just have'nt found them. But my stem hole measures 31.68 mm.

I have the front end off and am waiting on forks and getting the stem swapped out. I'll just take it down the Emig's where the forks are being done and have him do the stem swap also. I'm getting excited!

Also, what kind of bearing preload did you guys set on the bearings?

Jon.

KDX200Kev · Post by **KDX200Kev** » 06:30 pm Jun 25 2005

I am in the mist of doing a KX fork swap and was curious if you found a race bearing that would work with the KX stem and KDX frame steer tube? IMO that would be the best. If you went with the stem swap did you still knurl the triple clamp stem hole or just have it pressed in?

I have a 2002 KDX and 2003 KX - triple clamp (top and bottom), fork, and brake. I was thinking I did not need to knurl if the stem hole is the same on the KX and KDX triple clamp. Now I just need to find a 2003 front wheel (disc and hub are different then the other years).

Post by **Indawoods** » 08:31 pm Jun 25 2005

More than likely it will need knurled...
I have an 03 KX on my 95 and I don't think there is any difference in my and your frame. The bottom is the same bearing and race... the top on the other hand is nowhere close and I think you would be really hard pressed to find one somewhere.
There is a big difference in stem size at the top. You will also have to space the top clamp because the stem lengths are different, the KX being longer.

FWIW... I have a 01 wheel on my 03 and it works just fine.

KDXer · Post by **KDXer** » 09:42 pm Jun 25 2005

And I have an 02 that also works.

skipro3 · Post by **skipro3** » 01:17 am Jun 26 2005

I searched the world over to find a bearing/race to fit the KX stem to the KDX frame. No such animal exists that I could find.

When the KX stem is pressed to the KDX clamp, then you will know if you need knurling. It will either drop right in (needs the knurling) or it won't. (needs just to be pressed in)

Dang if I can tell what years KDX and KX's cause this. It's not a big deal either way. Most shops will charge maybe an extra 15 bucks or so for the knurling on top of the $15 bucks or so for the pressing.

BTW Kev, Glad you made it here from "there" I knew you were looking to do the KX fork swap and couldn't just sit by and watch the idiots give you such bad advice I was seeing.
Your buddy, Woodsquest AKA Skipro3!!!!

KDXer · Post by **KDXer** » 02:03 am Jun 26 2005

skipro3 wrote:When the KX stem is pressed to the KDX clamp, then you will know if you need knurling. It will either drop right in (needs the knurling) or it won't. (needs just to be pressed in)

Or in my case the stem turned down ?!?!? Stupid aussie crap.

skipro3 wrote: Most shops will charge maybe an extra 15 bucks or so for the knurling on top of the $15 bucks or so for the pressing.

Or in my case $200au, oh but I got a pretty brass shim too !!!

KDX200Kev · Post by **KDX200Kev** » 12:41 am Jun 28 2005

The KDXRIDER site is the BEST.

I thought the other site was good but now I know better. What was the name of that site now?

KDX200Kev · Post by **KDX200Kev** » 12:49 am Jun 28 2005

Thanks Skipro3 I really appreciate the input. It helps to clarify what I need to do regarding the decision to knurl or not. I spoke to BRP which is in my part of town and they will press the stem in for $15 but are not set up to do the knurling.

Post by **Indawoods** » 01:04 am Jun 28 2005

Kev... we wouldn't pull your leg!
If it's KDX!
This is the place.....

Post by **KDXGarage** » 08:03 am Jun 28 2005

KDX200Kev, welcome to the group. I think you will find the attitude and information here to your liking.

canyncarvr · Post by **canyncarvr** » 04:10 pm Jun 28 2005

Consider using the Loctite locking agent MADE for cylindrical press fit pieces.

!CLICKY!

It will matter a whole lot how good your measurement tool is. Depending on what metals you're talking about the difference may only be .001" anyway. You could miss that with a one-each set of calipers.

Check out the Loctite spec sheets. Their stuff is good for .005-6" (as I recall). Besides, the whole idea of the stem needing to be pressed in with a gazillion pounds of grunt is bogus anyway. The clip on the bottom of the stem will prevent the stem from pulling through the bottom clamp, the fork tubes will keep the top and bottom clamp in line. A huge amount of 'stick' in the stem/clamp fit isn't required.

The Loctite agent is good for around 3000 psi shear strength (depending on which type you use). Note I'm not referring to a thread locking agent but a product that is DESIGNED to affix cylindrically slip fit pieces.

Preload on tapered rollers is fairly standard procedure-wise. My preference: While rotating the stem/clamp back and forth, supporting it from the bottom, tighten the top nut to good-n-snug..probably in the 10-15ft/lb. range. While continuing to support the clamp loosen the nut and re-tighten it good-n-finger tight. Well...finger+ a tad.

How's THAT for exact?

Check the forks after your first ride. If you notice ANY movement of the stem 90º to the stem axis, tighten the preload nut a bit.

If your forks do NOT move freely lock to lock after you put 'em in (and you have no cable/brakeline interference), something is wrong.

skipro3 · Post by **skipro3** » 11:11 pm Jun 28 2005

I agree with CC on every point from my personal experiance. I couldn't have said it better. Read carefully the Loctite part. There are several versions of "Green" loctite so check the lables. I believe CC told me the one he ended up with was a rare find so I don't know where to get that stuff. Can you elaborte on the loctite CC?

canyncarvr · Post by **canyncarvr** » 12:57 pm Jun 29 2005

It's in the !clicky' thread text above.

Yes there are several types of 'green' Loctite. Two of 'em are designed for this purpose, one is not (it's a wicking thread locker).

Not really 'rare'...just not something found at your local Kragen's. I ordered it from a Sasco fastener place.

I'll send you the bottle if you like. A couple of rules, though.

You have to either send it to another KDXer that needs it (prefered) or send it back when you're done. Postage back will be a whole lot cheaper than buying a bottle of it..guaranteed.

Here's a BTW for 'ya, too.

There is a procedure for putting on the front wheel. The wheel needs to centered/positioned correctly before the axle affixing hardware is tightened up. Either spin the front wheel (off the ground) and hit the brakes or hold the front brake and compress the forks...THEN tighten the clamps (or whatever your style of fork uses).

Let me know.

skipro3 · Post by **skipro3** » 12:04 am Jun 30 2005

Doh!!!!!!!!!!!!!

I'm so slow, someone quick! Pull the plug!! I said no machines!!

BTW: That proceedure CC mentioned at the end of his last post will help in prevention of stiction.

IdahoCharley · Post by **IdahoCharley** » 10:37 am Jun 30 2005

The aforementioned information is all very good. I'm going to comment anyway just because I can......LOL

Loctite and/or knurling would be the way I would go. An interference fit of couple thousands is definately desireable. I'm not sure what a interference fit with a gazillion pounds of force equates to, but if the stem dropped straight into the lower triple clamp without an interference fit; the loctite would not be nearly as effective binding/locking agent.

CC is right that the fork legs and stem clip should keep everything in-line and stationary and I agree that a lot of stickem is not necessary to keep the triple clamps from pulling apart. But does not the stem also transmitting forces to the head tube on the frame? Some of the forces that are transmitted to the frame via the forks are tangential to the functional plane of the forks. Are not these forces the ones that could eventually cause the stem to loosen within the lower triple clamp? (due to minute rocking action of the stem leading to elongation of the stem hole - if the stem was not a tight press fit?)

P.S. I'm just thinking that 250 lb bike traveling at 15 mph (22fps) hitting rocks, logs, etc and maybe occasionally sending the rider over the bars (down tree in grass) transmits quite a bit of force through the fork legs (3 foot levers) into the lower triple tree and into the frame. Loctites shear force of 3000 psi starts to look ?? or maybe it doesn't.

canyncarvr · Post by **canyncarvr** » 01:30 pm Jun 30 2005

I've wondered the same thing.

IC wrote: Some of the forces that are transmitted to the frame via the forks are tangential to the functional plane of the forks.

Has always seemed to be that the 'Some' of that statement is one heck'uva LOT. I don't know how the tapered rollers live through it. Considering how hard the metal of those bearings/races is to handle that load and the diameter of the outside race..those same forces are on that little stem just stuck into a hole..into a hole in a piece of aluminum fer 'crin out loud.

I'm not a mechanical engineer. Well, no kind of any engineer, so guess it's no wonder that I don't get it.

BTW...look at a slightly failed stem bearing (not a crusty mess of rust that is a complete pile of crap) and you will see the effect of the tangential force that IC is talking about. The outer race will show wear/failure on the upper/outward surface only. They (the bearings) sure aren't going round and round like a wheel bearing application!

SOME folks take that race out and turn it around some when it looks like that!

skipro3 · Post by **skipro3** » 08:13 pm Jun 30 2005

I think the forces are spead out over a period of time due to the suspension action that takes place. If the forks were rigid and did not move to absorb energy, then the hits would be very violent shocks and the bearing surfaces would smash out sooner rather than later. But since the forks distribute that engery from an impact over a period of time, then perhaps the load isn't so bad?

What the hell do I know anyway.

canyncarvr · Post by **canyncarvr** » 10:29 am Jul 01 2005

Enough to full well realize that I'm riding in Prospect a-l-l w-e-e-k-e-n-d l-o-n-g ....and you're not!

heh heh heh....

BTW...I recall (I think) a question regarding the stem diameter at the bottom bearing..whether it was tapered or not? Think it had to do with jafo's setup with a washer on the bottom of the stem.

Using a caliper with .001" divisions, my stem is .0015" wider at the bottom than at the beginning of the bearing seat area (I'm sure there's a word for that turned surface, but I don't know what it is). I wouldn't call it tapered really...but it does start smaller than it ends up. A reasonable way to get the bearing started I suppose. The interference fit of the the stem/bearing is 'about' .001". ...a bit more.

skipro3 · Post by **skipro3** » 11:51 pm Jul 01 2005

I asked what I know, not what you know. Learn to read. Words do mean something ya know!!

Hope you are having a blast this week. Photos!!!!

KDX200Kev · Post by **KDX200Kev** » 11:30 pm Jul 11 2005

Indawoods wrote:More than likely it will need knurled...
I have an 03 KX on my 95 and I don't think there is any difference in my and your frame. The bottom is the same bearing and race... the top on the other hand is nowhere close and I think you would be really hard pressed to find one somewhere.
There is a big difference in stem size at the top. You will also have to space the top clamp because the stem lengths are different, the KX being longer.

FWIW... I have a 01 wheel on my 03 and it works just fine.

Did your KX front wheel rim have the same style as your KDX rim? Or did you relace the KX hub with the old KDX rim?

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Stem sizes.

Stem sizes.