USD forks? Why?

[jgas]

Unless you ride only SX style MX, why would you need USD forks on a KDX? With a fork brace, the right springs, and a revalve the late model KDX forks will do most anything from MX to Singletrack. The fork underhang sucks in some ruts, that's the only thing I can see a problem with. We had a local fast kid who rode a DX with a Fredette revalve, fork brace, and Fredette motor and was the local MX track champ and rode AA in Harescrambles with the stock forks. What am I missing? "Cool factor"?

[plb]

My friends try all the best mods for the stock fork (change springs, put Race Tech gold valve on it, adjust everyhthing for his weight, etc) and now, he rides a KX250 2001 forks.. It's the day and the night!!!

For me, I put stiffer springs on stock fork and after I put a brand new KX125 2005 USD. With appropriate springs and enduro valving, it's awesome!

You CAN'T compare a KDX forks and a recent KX fork.

Stronger, stiffer, better handling, etc etc etc...

And, the USD fork don't have the two fork legs under the front hub (I crash sometimes when the legs hits the mud or rocks). Better clearance.

[canyncarvr]

Re: 'The fork underhang sucks in some ruts.'

Yep...and most every other kind of place I ride. I got flipped a few times with those things. They suck.

[youtube][/youtube]

That's not me..and it still hurt.

My OEM forks were MX-Tech valved, Honda sprung (hot-wound XR springs). They worked great.

I thought.

Rebound control is a big deal. You can't get rebound control with a viscosity change that you can with a fork that has a valve for it.

Rigidity is a big deal. I was never happy with my WER on my OEM forks. It didn't accomplish anything. I'd read others complain about the 'spaghetti'-ness of the OEM forks, didn't understand what they were talking about. It was never a problem for me.

Until I put my USDs on. NOW I understand. My WER actually does something, now.

So:

1. Underhang gone.
2. Rebound control.
3. Rigidity.
4. Tunability.

Between the base valve and mid-valve on a Kayabe USD set..you can make 'em do anything you want 'em to.

Cool factor?

I couldn't care less.

[Julien D]

No possible way I could have set it better than this...


So:

[quote]1. Underhang gone.
2. Rebound control.
3. Rigidity.
4. Tunability.

Between the base valve and mid-valve on a Kayabe USD set..you can make 'em do anything you want 'em to.

Cool factor?

I couldn't care less.[quote]



Thanks Carvr!

[Indawoods]

I only wish I had a video of me at speed doing a face plant when the right fork stuck a rut....

I almost lit the damn thing on fire when I came too.....


It is the single best safety feature that you can do to the KDX besides a stabilizer.

[jgas]

I guess I'm not fast enough to need what you guys need. I have USDs on my KTM and hate em. I have had USDs on many bikes, always hate em in rocks and roots. They just don't ever seem to be supple or reactive enough to not deflect on the small-medium stuff. I like my 02 DRZ 400 right side up fork much better than I did the USD-WPs on my 04 KTM 250 exc, even after a revalve and the 3rd bushing removal on the KTM forks. In fact, I am probably going to put some conventional WP 50mm forks on my KTM, or some DRZ forks, whichever I can get the best deal on.

I also find that I have to do at least twice as much maintenance on USDs. The oil gets dirty faster, they allow dirt under the seals, the seals leak or completely blow, and I can feel the deterioration of the oil much more than I can on conventionals. I usually change fork oil about every 12-18 months on most any conventional fork. On USDs, either the seals blow, the oil stops working and the forks don't work and I feel the change in action within 6-8 months even if they aren't leaking. The fork seals on my 02 DRZ are original! Never leaked or caused any problems. I change the oil by draining and refilling about once a year and they just keep working.

The only USD fork I have ever used that I liked is the Showas on the 07-08 Honda CRF-X. It is the only USD fork I've ever tried that actually soaks up the small medium chop without deflection and will still take medium-large jumps without undue deflection or bottoming. When I rode an 07 Honda 250X in tight Singletrack, I loved the fork, first USD fork I have ever liked. I admit, I'm just a B rider and rarely ride MX or even high speed stuff, I'm mostly a Singletracker in nasty terrain where the speeds are generally lower. I guess thats why I like KDXs. I am faster on a stock KDX than on most any MX based bike, and at least as fast on a stock 04 KDX as on my modified KTM 250 EXC. A KDX is 30% less money and at least as fast for me, with less maintenance as well. Not knocking KTMs, they are great bikes but more than I seem to need at my level.

Now, the underhang issue, I can't argue with! I have also crashed from hanging the fork on stuff and of course I want to take the forks off and beat them into aluminum foil with a sledge hammer.

[Julien D]

I'm mostly a Singletracker in nasty terrain where the speeds are generally lower.

Me too. If you can't set up your USD's to peform better in ANY condition than the non-adjustable KDX stockers, you're doing something wrong. Sorry.... Maybe find a new suspension guy?


J.

[canyncarvr]

It's interesting that you mention the CRF Showas...I thought they were picture-perfect myself when I rode that bike. Using that fork set-up as a comparative base, I think my KYBs are awfully close.

And, trust me...it has nothing to do with anything even faintly related to me being fast. That's simply hilarious.

I wonder about the troubles you list. I ride a good bit..and have never had a seal problem on my KYBs. I change the oil in 'em maybe a bit more often than you indicated...but not by much.


I use SealSavers (long ones). I haven't tried the forks with AND without them to document a difference in seal longevity, I'm just convinced I never want to ride without 'em. I see unprotected (guards but no SealSavers) USD bikes full of mud with the inner tube fork travel wiped clean and can't help but wonder how the seals can possibly deal with such an environment.

They probably don't.

One problem I had with the OEM KDX forks was pressure build-up. I had poppers on 'em..and used them to release pressure several times a ride. My USDs don't do that (build pressure). Don't know why...they just don't. BEFORE I put the pressure bleeders on my RSU forks I figured the handling problems I had with my bike was due to my getting tuckered toward the end of the day. I was amazed at the extent to which fork compliance suffered from that pressure and the huge difference it made when I could vent it out of the forks.

Guess that doesn't fit into the subject-at-hand. Call it another reason I like the USD forks.

From just the suspension (hydraulics) point of view...my RSU forks worked great! If it wasn't for the underhang and what I learned of their flex-factor I would have never considered USDs. ..and I'd still have my odo!

In the end..what matters is that you ride what suits you. To say you prefer RSU forks having never had anything to do with USD forks is silly. Having experience with both types and preferring either over the other is just that..a preference.

Still, I can't help but wonder if there isn't more to be discovered..tuned, say, about your USD experience.

Besides...they're so COOL!!!

[fuzzy]

Should add that they are simply an easy and cost effective swap as well when using Kawi donors. The 'better' USD's can be had and swapped in for less than the brace/revalve/blah/blah. You're right though, pretty much all factory susp will need tuned for your weight/style/liking. Having the adjustments is important. GOOD RSU forks would be the ultimate, IMO, but harder so swap (IE Showas).

[KarlP]

Jgas found his '02 RSU forks better than most USD he had used in the woods. I'm not surprised. I've always thought that a good RSU ought to better for the woods than an USD

For the KDX guys we are going from mid '90's era RSU with limited tunability to an USD from an entirely different bike style. That is a big improvement over the OEM RSU on the KDX.

I've heard good things about the DRZ RSU forks. A buddy of mine switched to XR400 forks on a CR250 for the woods.

[Indawoods]

Well sure... a new set of modern RSU forks is the bomb!

For one... they are very expensive, for another... they are very hard to find.

Comparing a 43mm KDX RSU's to 48mm modern RSU is a joke. Or to 48mm USD's.

43mm forks period are under spec'd.

[Slick_Nick]

Is there a way to run the KX USD's and still keep my stock trip meter?

[Indawoods]

Sure... have an axle made to fit your KDX front wheel to the KX forks of your choosing.

[Slick_Nick]

Will the KX front caliper work with the KDX rotor? Or at least will the KX rotor bolt up to the KDX wheel?

[canyncarvr]

The general way of doing it is to use the KDX caliper ('cuz you have one already), bolt it up to the KX fork, use a KX wheel.

The KDX rotor does not bolt to a KX wheel. Well...mine wouldn't. I suppose there might be year-X of one that fits year-W of the other.

For what you're after you could use whichever caliper..as long as it bolts up to the fork. If you use the KDX wheel, where its rotor sits would be part of the axle/spacer making.

There have been riders that have used the KDX wheel on a KX fork-set..primarily to use what they had..AND them being machinist types with the ability to MAKE an axle.

You can use an aftermarket odo (magnetic driven) if it's miles/mileage you're after.

[Slick_Nick]

I would like to use as much KDX stuff as possible. Not because of money, but I love the bike as it is, tripmeter and brakes included! The forks awork great for me as they've been resprung and revalved, but everyone says taht once I do the swap I'll wonder how I ever rode before.

So I'd just need to manufacture or find an axle and spacers that will work with the KX forks, and I'd be set then I guess? I really like the stock trip, I don't want a bulky big enduro computer up there, I love the simplicity of the stocker.

[canyncarvr]

I would like to use as much KDX stuff as possible. Not because of money, but I love the bike as it is, tripmeter and brakes included! The forks awork great for me as they've been resprung and revalved, but everyone says taht once I do the swap I'll wonder how I ever rode before.

That's a bit of an overstatement. A USD set is better in a number of ways..and if none of those ways matter to you..why bother?

Something you might consider: Look into getting a second KDX stem so you don't have to get yours out of the KDX forks. If it's something you're going to be doing yourself (the stem removal/insertion) then it doesn't matter much. Fredette would be a good one to ask.

But..if you decide you like the OEM forks better, if you have NOT swapped your KDX stem, a retro-fit will be a lot easier to get done.


Re: '...and I'd be set then I guess?'

More or less. See that boss on the RH RSU fork leg that orients the odo tab?

...don't got one'a those on the KX forks, but you could come up with something that works.

Another thought..I don't know that there is enough room to mount the odo drive and center the KDX wheel if you HAD an axle. You would want to get that all sorted out before you got too far into machining an axle...or figuring out what one would lilke even.

Oh..another reason the KDX caliper is used is that a hi-route for the brake line is generally considered preferable to the KX caliper lo-route. The KX caliper can be used for a hi-route with a bit of modification...a different angled banjo and some grinding on cooling fins that will be in the way.

You will likely find some catches in the process..but it's all doable. Not too long ago one fork-swapper had a lower stem bearing that wouldn't seat to the bottom clamp. That was the first one'a those I think. RB-Designs reduced the stem diameter a tad as I recall so the bearing (well, the seal) sat snug to the stem as it is supposed to.

[pdiddy]

I so want to do this to my bike!!

Must...........find...........KX Forks...............on................ebay!

[Slick_Nick]

I've read about the better brake line routing on the KDX caliper, another good reason to keep it. I'm fairly confident that I want to do the fork swap this winter, but I would have to figure out something to mount the odo drive unit...

[canyncarvr]

Re: 'another good reason to keep it.'

Again..most use the KDX caliper in large part to already having it on their bike, so, why buy something you don't have to? Another part of that...if you use a KX caliper and lo-route the brakeline..you need a KX or aftermarket brakeline..the KDX line isn't going to reach.

All supposition (not to be confused with anything suppository), but I would imagine you would need to have the KX forks mounted on your bike before a determination could be made as to what is required to fit the KDX wheel. The measurements exist (width of KDX hub, odo, RSU fork width as compared to all that in the KX setup) because it's been done..but I don't think you'll find them anywhere. Besides, I would want to make sure whatever was being manufactured for my setup FIT my setup, not what someone else measured.

You're not going to walk into a machine shop with USD forks in one hand, a KDX wheel/odo in the other and say, 'Can you make me an axle for this?'

Not without getting laughed out the door anyway.

I'm not saying it can't be done. With the lower triple, fork tubes and the KDX wheel/odo, it could all be figured out. What isn't likely to happen is finding a machinist that wants to spend that much time..with YOU willing to pay him for his time.

You haven't said if you're the metal-guy going to do the work or if you would find a shop to do it. If the latter, talk to them to start with, figure your options from what they say they need to do their figuring.