Too Cool not to share III PDS Springs/ Topouts

Jeremy Wilkey

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#1
Great points and questions BTW.. Yes In some ways I think the whoops bring out the most glaring problem with the PDS shock. But that is not in anyway to say that the whole rising rate issue does not affect woods riders.. After all Off-road riders still have to deal with big holes, high-speed natural whoops and river banks, it’s very relative.. And its not 20 yards long like on the MX track.. Anyone can pin it and hang on for dear life for 3-5 seconds right...

In my really misguided past I only used one shock piston! So I really have an appreciation for a linear shock system, and believe me you want the progression.. The cool thing is the PDS brings it in later than current Linkage bikes which means most of the nasties you hit you hit with less damping than a link bike that comes in right after sag.. As for the new needle it does bring it in sooner but it’s still pretty deep and again because we have more strokes to take advantage of the added compression we can run it way lighter so the "transition" seems much smother.. I could go on about SX situation where I think PDS could be an advantage with the new needle but I'll leave it be.. In really slow conditions the new needle might be a little much, but again that’s for the guys who also need straight rates, so if you don't get out of second then well the old set-up may be better, but so is one piston.....


I know lots of guys who tried PDS springs with the STD 04 set-up and found it imedalety better, I even know KTM regional reps that have become very outspoken to upper management about how bad the new stuff works, and these are off-road riding reps BTW..... When I first rode an early version 04 shock, I could not believe how hard it bottomed on the MX track... It was ankle breaking bad when I came up short on anything big... I put a progressive on it and it felt better but was still soft, it just felt less hinged... As for valving, I think that would be best, but from experience I can say I think its better right away and more than ride able.. For what its worth I think some of the guys I've read on this forum run PDS rates that are two stiff as well.. Set the sag at 35mm and forget about it.. Checking rider sag is a Pandora’s Box... I run a PDS #6 on my 125 and I weight 215 with gear.. I'm sure I've got 120+ but it works great.... If I run a 7 then I have to run .44's in the fork and the bike gets a heavy dead feel....

The top out spring accomplishes a couple of things... First it effectively makes the main spring softer once it is engaged. So the bike has less spring force until you compress the shock beyond the point of negative preload.. Secondly this means it allows the wheel to float up and down as you traverse small undulations with out significant spring force, making the shock more compliant.. We've done data acquisition with and with out and the shock has much more subtle small movements at or around extension which translates to improved traction and control.. So yes I'm a fan, I also insist on running only 35mm-40mm free sag no matter what spring you run for this reason.. It would benefit many if they had a stiffer rate Top-out for the stiffer PDS springs, but that’s not available yet..
 

Jeremy Wilkey

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#2
AH.. Very interesting purpose.. It’s for this reason that I worry about balance front to rear.. My view is that as long as you have the right spring with the right preload the variables will retain consistent, but I never chose the rear rate until after I've chosen a fork spring rate... I do think there are some problems with big riders using the PDS springs but I still think it’s a lesser compromise than a straight rate..

I've noticed some comments about head shake etc.. I have to add that I spend very little time working with stock KTM's.... I agree that steering dampers can mask bad suspension, but generally they are fine, and don't detract from the system once its set-up.. I don't find we ever have problems with head shake... To spice things up, JD runs a steering damper I wonder what that means?

Anyway as for the Ohlins PDS I've been in the process of testing one and I don't like it as much. I really think it would be a lot better with a Progressive spring.. The bike is hinged feeling with it... It might be better than stock, but not nearly as good as the set-up WP.. I think the draw has been the way the overlap occurs with the Ohlins, now I think with the new needles the WP has an advantage, but I'm still working on making the Ohlins better.. What I find interesting is when you put the Ohlins on a bike it draws a crowd.. I've got works Twin chambers, works shocks and only a few ever notice but that Gold Urban colored "bling bling" on the bike and everyone comes over and goes its awesome! Excuse me.. Did you want to look at the times? Ohlins has branded the "perception" of performance, and I think as far as the suspension available to US riders it’s all myth... Ohlins has nothing cool (out of the box) for me or you.. John Curea and I have been trying very hard to change that but just like KTM initially it seems to fall on very deaf ears..... JC has recently made a bunch of progress with his projects, and I think I've found some better channels with connections in Europe, so hopefully we can actually soon tap into the brain power and real capabilities of Ohlins.. Because from what we can tell it’s not in the US....

BTW the way to your original question the Ohlins uses a recessed cup in the top of the shock and a smaller piston on the top of the standard shock piston. When the small piston travels into the cup the taper of the cup determines how much bypass occurs and ultimately what the damping coefficient is based on speed. It’s a 180 from the needle twin piston design of WP... WP is using the "Ohlins" concept on the new 85 and actually the details are foggy but its all "ohlins" ideas... I don't know the facts only 20 different stories... I do know the first time this idea was used was the 80's twin shock ITC Ohlins used on the huskies..



I agree with Fishead 100% with the exception of I believe that we are there already.. The WP suspension when set-up is actually better than a set-up linkage bike.. I'm inserting my biases based one my ability to set-it-up better than others, but whatever.. What upsets me is that we KTM riders walk around accepting that our bikes are cool, light, nimble, and fast and well made to suffer comments about the suspension is crap... Its not, and I've been trying to prove that for some time... I often let riders ride my 125 and they get off and go "wow" I knew they where fast but they handle too..... Anyway as long as KTM continues to not "Cross pollinate" with each other they will stay where they are, with 250 riders afraid of the bike and not getting where they have the potential to grow by making quick decisions not based on solid data.. It’s a one step forward ½ step back kind of relationship.

As a WP distributor, as a tuner for the factory team I've never been told why Straight rates are better!! Think about that for a minute....

In conclusion I think that’s the real problem that I see with our industry and KTM and many others. Sometimes Ideas are not argued on technical merit, decisions are not made on logic or corroboration within the company, taking advantage of all its techincal diversity. (There is no shortage of talent). Its time to let fear not be a guiding source of motivation....



BR,
Jer
 

DEANSFASTWAY

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#3
You know what happens quite often Jeremy is that once some West coast test rider for some crappy magazine rides a bike with a different color than hisusual flavor he gets jaundiced. He doesnt tsake the time to really evaluate the bike because he alrady knows what color fenders it has . He is swayed by past history or what he has heard and doesnt really give a good test on what is perceivred only on what he already thoughtor was told. Plus there may not be someone there thats reall familiar to set up the bike. If you have a KTM and the rear is not correctly set the rear may ride high and front end may shake or if its too saoft the rear drags low and the bike skates. If everyone always complains about KTM (SX) riding high in the rear . Why would the want to go to straight rate springs only to have no curve . Progressoives offer more plush . I even like to find progressives on woodsy bikes or for more lightweight riders, you know the springs that everyone was taking off the 00 Kaws for example . PDS systems are by far the most tunable systems manufactured Esp WP, if different needles were readily available there would be a big benefit . On older KTMs I used to try to shorten or cut a taper on the needles but I couldnt really perceive much of a difference myself . What other system can you tune like this? There are only a handful of linkages available for Jap bikes and as such what are the prices? I think what bothers most users or consumers is the big degree of difficulty in service of WP. Alot of guys like to change their own shock oil but are scared to try a PDS . Special tools etc. Maybe thats a good thing if they dont want to open up a big ball of wax . Maybe they just need to get educated a bit more. I know I can make a KTM ride like a Caddilac if I want to and still soak up the gnarlies or stay atop a 1/2 mile set of whoops. A fellow recently asked a question on this forum it read " Which first correct setup suspension or steering dampener?" It was from an east coast probably dual intent guy MX/ offroad I think he was from Jersey . I see alot of orange bikes out here with dampeners but probably stock suspension . If you really take the time to tune you shouldnt really need a dampener albeit maybe in emergency to save yourself or something . Another thing KTM esp(no locknut) is that it seems alot of riders dont know how to set the steering head bearing properly , theyll have a dampener cranked in and loose steering bearings . ??? The bad press KTM gets is a big farce. The Ohlins thing Ive kinda got to agree with you on and it the same as like 8 years ago when the mags were pushing on selling the 45mm Marzo forks ? What a load of crap they were, but people gotta love the Bling Bling . Those new Ohlins ZPS Fully adj Quad shocks that are out are pretty nice though.Ah yes one day KTM will become a mainstay and there will be much more on the MX gates but for now youll have to go to a Enduro or HS to see that at least 60% are on orange bikes . Out here anyway.And Jer from a production standpoint Im sure its cheaper to respec aPDS needle or shim stack configuration then to go with the Progressive spring. The pro spring just costs more . It would really be bitchen to get the trickest susp on a bike with the best motor that already comes with the best bars and chain and stuff. Nothing is ever perfect my friend. At least not me thats for sure. But I agree with your points and you and I have talked this before that its not only to do with you relationship with the KTM brand. CHEERS DEAN
 

svi

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#5
Jer,
Would you still see the need for progressive springs on PDS shocks for flat track or supermotard where a more linear spring rate might be advantageous.

What would your thoughts be on dual or triple springs rather than a wound progressive, I've been playing about with dual's and triples on some quad stuff but I need to seriously sit down over the winter and get my head round it all properly.
 

Jeremy Wilkey

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#6
SVI,
We've been running progressives in our supermoto program, and DTX bikes.. The bikes break the rears lose better with straight rates but they are very hinged in the back and don't work nearly as well in all other situations..


As for the stacked spring, it offers control of knee points, but it is somewhat jerky, and continues spring offers a more subtle transtion..
I have some software written by our friend MACE that I'd like to share with you. Drop me an e-mail. IT will allow you to get your head around it..

BR,
Jer