PDS shock workings and history.

[dthoms]

Marcus,
Yes I do have the 43mm forks, I thought they were 45mm but I put the caliper to them and it read 43mm, my RMX has 45mm and I never felt a flex problem with them. However I can ride my KTM at a much faster pace than the I ever road my RMX.
I have taken apart a lot of forks and messed with valving and installed gold valves, but I have always sent my shock work out. I have a very little understanding of how the valving works, my best luck has been with trial and error changes. Not always sure why what I did worked.
One of the things I like about my suspension on the KTM is it's ability to jump small and medium objects( roots, rocks, stumps, logs, whoops) with out a lot of rider imput. On my RMX if you want to jump over something you better be forecasting it, you will need to make sure you hit it square and preload the suspension and be on the pipe, and if the whoops are to long sandy and deep you will run out of power, and suspension.
With the KTM usually a quick bounce and a blip of the throttle (sometimes just one or the other) and your up and over, if the bike get a little crooked it straightens out nicely under power. And running out of power is not a problem.
Are there replacement shims for the compression dampener of the fork that would help the mid stroke harsheness, but not hurt the pogo effect?
I would have to agree with the "Pretty Damn Stiff" label for the shock, I have my set up pretty stiff, but the faster I go the better it seems to feel. I have rode other brands that were as good as mine in the fast rough stuff, and more plush everwhere else.
The problem with me is that I'm old and I can't keep up that pace for more than a couple of hours (or is that minutes?) or so and then I struggle with the stiff suspension until the day is done. I will get a second wind but that doesn't last long anymore either.
What I really want is cheater bike that I can ride all day and it doesn't tire me out, and gets 100 miles a gallon, and no maintenance for the first 100,000 miles.
Also on the PDS what would a higher level of lighter weight oil, and perhaps a higher pressure nitrogen charge do for the progressive feel of the shock?

 

[John Curea]

Sounds like it might be time to try a 2 stage stack on the secondary piston.

Russ, you old restless coot, I think I'll nickname you Gandolf... ;)

 

[marcusgunby]

John thats the setup i ended up with:)

 

[dbrace]

What's a coot? and where can i find one here in the land down under?

 

[marcusgunby]

Right back on topic, the pds main advantages are in theory light weight simplicity and cheapness and no greasing, lets break these down

light weight, well i havnt weighed the system but the KTM 125 isnt as light as a CR125 or a few others, this doesnt prove the PDS is heavy but it hasnt helped the bike much, the 250sx however is the lightest of the 250s but thats probably down to the rest of the bike-inconclusive this one.

Simplicity-well it is simple to remove the shock but then when the shock need servicing-then it costs more.

Costs-well a KTM costs a tad more than a jap bike but comes better specced.

Greasing or lack of-well many KTM owners now hate the spherical bearing-i did however get good service from mine. However KTM owners dont spend hours in  grease with rollers all over the floor.

So overall i would say its 50/50 on the disadvantage/disadvantages.

 

[DEANSFASTWAY]

Marcus I put a 00 KTM PDS on a aftermarket framed 450 race quad . It had a CR500 linkage setup on it . I set it up as a ZPS zero preload system. It worke sort of hacky at first Then we trimmed the needle way shorter and changed stacks a couple times. I also played around with no needle or short needle and closed or partly closed piston bypass hole ( hole in spacer between pistons) .I also thught about removing the needle and installing a jet in the end of the shock shaft but that would disable the secondary affect and we wanted to keep it functioning.I thought I could valve one piston for low speed and one piston for high speed and quickly tune shock bypass with jet. Actually theres alot of tunability in these shocks and maybe more than most people could utilize. I can get these KTM bikes working really plush in the woods and rocks but it seems that some are just setup too firm stock.Ive seen a few of John Curyeas riders in the woods and they look really good also . In the end we got the quad working real good and the rider had some sucess with it. Wilkey and I talked about this a bit. Alot of quads come with cheaper small bodied shocks that dont really cut it . The problem with PDS changeover is that its hard to find used shocks. We tried CR500 and like YXKXRM shocks but the reservoir is in the way of the exhaust . Maybe someday Ill post some pics. PEACE from the East DEAN

 

[marcusgunby]

Dean your just crazy ;)

 

[DEANSFASTWAY]

Sometimes we like to use whats available ands with the cost of AXIS and ELKA and stuff sometimes we needto cut costs . ELKA and AXIS and OHLINS and B/A WPS are good though . We just kinda wanted to use a PDS.

 

[MACE]

Originally posted by marcusgunby
drehwurm so nice to have you back-i knew it would just take the right thread to bring you out the closet so to speak.Ross is keeping me plenty busy:) but i wanted to spark up the forum with a good debate.

Better lock the door or the real dregs will creep back in... :yeehaw:

 

[Jeff Howe]

Now there is a guy I have missed for some time. How you been Mace? Yeah, I'm probably one of the dregs he speaks of.

 

[MACE]

Before anyone misunderstands, the dregs be me...

S'nut, how you?

I'm so ashamed.

My bike needs servicing. I have the parts on hand. And instead of doing the rings, fork and shock, I put on new plastic and graphics. Thought maybe I could get a dose of priority therepy here.

...but those MXDN replica flag graphics do look "cherce"....

 

[Jeff Howe]

Naw, depends who you ask.
I be fine.
I need to make my bike pretty again too. Most all the mechanical stuff is tight, just looks a little rough from lots of seat time this year. I do my makeovers in the winter. You been hiding out a long time bud. I was just thinking a couple weeks ago about where you had gotten off to.

Back on topic, I got a PDS shock laying around here Dean, it might go up for sale next spring. 00 SX 520 I beleive it is from and if you still might want it then we can work out a deal maybe.

 

[DEANSFASTWAY]

Sounds good Shocknut, Just let me know when , Maybe we could use it.

 

[tonynz]

I had a Ohlins shock on my 01 520 it worked not too bad, but could never get it dialed in properly not many of them in New Zealand as in none.
On my 03 525 I had the WP revavled different spring etc by a Australain suspension expert and it works really well.
So the Ohlins shock is an expensive paper weight in the garage.

 

[DEANSFASTWAY]

Wow a contradiction from the usual opinion. Actually I like the WP except for some of the maintenance issues.

 

[Garyb]

Tony - want to sell that Ohlins?

 

[marcusgunby]

Ive got a little gossip for you on the works PDS-well it doesnt use the needle and 2nd piston the production shock has-it uses a ............. ohlins type setup.
Also on your shocks check the part where your boot runs on the N2 bottle-a few riders have worn all the way through and the gas has come out.

If you find any oil on the lower clevis of the shock, inspect the shaft entering the clevis-it maybe loose.

 

[prcucuma]

A friend of mine has an ohlins shock in his husaberg. But besides it had quite an impact on his wallet, it doesn't seem to help him so much. After spending quite some time with him on different tracks I can't imagine there is such a big difference between the wp and ohlins in performance.
When I had a linkage and swapped to an ohlins there was quite a difference though...

 

[marcusgunby]

A badly setup ohlins will be far worse than a good Wp.However its when they are both well valved and setup-which one is better-i dont know as i gave up on KTM in 01.

 

[bclapham]

Originally posted by marcusgunby
Also on your shocks check the part where your boot runs on the N2 bottle-a few riders have worn all the way through and the gas has come out.

have a look at this to see what happens when a SIDI boot and a PDS shock stop getting along!

http://www.dirtrider.net/forums3/showthread.php?threadid=72926

 

[drehwurm]

Servus,

There is a good chance that the PDS's history will not be a long one. Possibly by 2005 we might see a linkage on SX/EXC KTM bikes again!

Talked to a KTM factory suspension tech in the pits of an upcoming Supermoto event here in Austria. More than a rumor? Don't know, but it is not unlikely from my point of view.

Michael

 

[Bezdelnik]

Where can I find what the different weight ratings are for the '01 springs? PDS1 vs PDS2...etc

 

[marcusgunby]

I wouldnt be surprised if we saw a linkage KTM in 05-many rumours were about this in 03 for the 04 model.

 

[bclapham]

so is it a case of trying to make a bike without a linkage is a totally flawed idea; or is it just a case of getting the shock working properly negates the need for the progressive linkage.

seems to me, that it would probably work OK without the linkage its just that getting the shock dialled is the biggest issue and this is compounded by the fact that not many people will mess with the shock since they dont understand them and cant get them apart.

the linkless 125sx cant be that bad can it- how many world championships has it won?

 

[blohman]

It is nice to finally hear the difference between the Ohlins and WP, that explains a lot as the bypass on the WP is deffinately restrictive. WP improved flow through the bypass after 98 but they are limited by shaft size, this is why they use an 18mm shaft. There is much more area available around the OD of the piston for bypass but the piston probably cannot form a tight seal against the shock body durring those last few inches of travel on the Ohlins limiting the amount of low speed damping that can be generated, perhaps that is not a problem. Do not use the KTM specs for pds spring comparisons, I have tested nearly all and the latest generation (5,6,7,8) are more progressive than 1,2,3,4. The newer springs get stiffer at about 1/3 travel and carry through hence offering more bottoming resistance but also more midstroke stiffness. I still prefer the new spring (today anyways) as for low to mid speed movements the bike handles better. I keep making the secondary stack softer and softer with good results while trying to find a good compromise between bottoming and midstroke stiffness. I think I will try Race Techs new spring so I can make the bottoming stack even softer.

It is really interesting to see KTM's 04 setup. For that to work they will definately need the longer needle but with a really soft bottoming valve stack unless they found a way to create more bypass flow. It seems that right when I am ready to give up on this system some idea comes along to make it a little bit better. All of PDS advantages have nothing to do with bump adsorption except possibly one, the inertia of the sytem may be less than a linkage allowing it to react better if the hydraulic flow issues can be solved.