Is there difference in jumping/landing PDS vs. linkage suspension?


26 replies to this topic
  • Bream

Posted 07 September 2011 - 12:23 AM

#1

Like the topic goes. Is there any difference with jumping technique between KTM PDS and jap bikes with linkage?

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  • Dirt Addict

Posted 07 September 2011 - 06:47 AM

#2

I've ridden both a lot. No difference that I can tell....

  • Bream

Posted 07 September 2011 - 07:24 AM

#3

Yeap, thank you. I have riden only KTM in motocross. And before I bought one. I did read some bad things about PDS-shock.. like they kick rear high from jumps easier and stuff like that. But it could also be wrong kind of setup like too strong spring. Another thing why I did this thread was that my uncles "tips" about riding are not working.. and he has experience on japanse bikes only. Could be also that he actualy dont know what he is saying.. :)

  • tye1138

Posted 07 September 2011 - 11:03 AM

#4

Well, not to disagree but yes, there is a noticeable difference between the two. The progressiveness of the linkless system is very different then that of a linked. You can resolve some of this by buying a progressive spring, the down side of the progressive spring is, it doesn't give you a "linear" feeling. As the bike squats, it gets exponentially stiffer.

I've used both progressive and linear springs on my KTM and can't find a perfect compromise. The progressive spring feels great around corners as it has a softer top end and allows the bike to squat more. The linear spring feels great everywhere else on the track. Instead of the bike squatting coming up jump faces or entering a whoop section, it feels planted. You need the instant stiffness to give you boost off jump faces.

These last few weeks, I've had 2 of the same bike to ride (125SX) one with a progressive setup and one with a linear setup. I've built both bikes to be identical in every other way and I've gotta tell you, what I talk about above is so true. I've been trying to diagnose a problem with the rear of my bike and by doing this test, I can clearly tell the difference between the two springs. Then I rode a linked 4 stroke with a linear spring and it felt like the perfect hybrid. None of the boost problems off the jumps and all of the grip leaned over.

I think people underestimate the value of linked suspension. KTM didn't just do it because "American's" were complaining, they did it because American tracks are a bit rougher and have obstacles that a linked suspension setup will benefit. Also, a linked setup gives you more adjustability (via the link itself) so you can change ratio of the stroke. Being able to change the ratio, allows tuners to help riders deal with some of those very difficult obstacles where you need boost (stiffness) but you also need compliance for everywhere else on the track.

My next bike will be a 2012 KTM 250SX with a linked suspension. As much as I like the simplicity of the linkless setup, I do feel its not the best way to approaching the rear end setup.

  • Dirt Addict

Posted 07 September 2011 - 12:04 PM

#5

i thought that ktm brought in the linkage for sx type riding, and because americans felt they needed it. i guess i'm not fast enough to feel the difference :)

  • Bream

Posted 07 September 2011 - 12:51 PM

#6

Heh, I read it from some magazine that it was Stefan Everts who said he wanted the linkage. So that he can make these new guys something special.. and it seems to be working on Cairoli and Roczen. :)

  • tye1138

Posted 07 September 2011 - 06:19 PM

#7

i thought that ktm brought in the linkage for sx type riding, and because americans felt they needed it. i guess i'm not fast enough to feel the difference :)


If you rode it back to back, you'd immediately feel it, completely night and day.

  • farfromhome63

Posted 20 September 2011 - 06:15 PM

#8

Tye I've got to slightly disagree on this, I realize you have two bikes setup the same, remember when you change springs you also need to adjust the rebound, the main difference was ktm was trying to counter act chain torque hence the close distance to the swingarm mount and front sprocket and to minimize weight, less un-sprung weight is the key for a better handling bike.

If the shock valving is identical with a linear spring and you dont change it to compensate then of course your going to feel it. But I personally dont think that it takes a different technique. I used to own one of the first link-less bikes an ATK 406 and Horst leitner was the inventor behind the idea, also side mounted shock with a atrak chain tq eliminator. I think traction is what would be the best perceived difference between an equally tuned suspension. If you are beginning just ride the bike and if it doesn't work for you adjust accordingly.

  • tye1138

Posted 21 September 2011 - 07:16 PM

#9

Tye I've got to slightly disagree on this, I realize you have two bikes setup the same, remember when you change springs you also need to adjust the rebound, the main difference was ktm was trying to counter act chain torque hence the close distance to the swingarm mount and front sprocket and to minimize weight, less un-sprung weight is the key for a better handling bike.


Yep, they were identical on the clickers, similar sag settings as well.

If the shock valving is identical with a linear spring and you dont change it to compensate then of course your going to feel it. But I personally dont think that it takes a different technique. I used to own one of the first link-less bikes an ATK 406 and Horst leitner was the inventor behind the idea, also side mounted shock with a atrak chain tq eliminator. I think traction is what would be the best perceived difference between an equally tuned suspension. If you are beginning just ride the bike and if it doesn't work for you adjust accordingly.


Yea, technique might not be the right word, I'm sorry about that.

Traction, boost off jumps and stability through whoops are really the biggest differences between the two springs. The traction issue is probably the strongest as these bikes are already spinning the rear wheel a lot, traction is at a premium as it is.

I have tried adjusting rebound, compression and preload to compensate and have only found a happy medium, not a perfect setting. Mind you, I have been working on suspension for years, so I understand the theory quite well, though I'm still new to motocross so I'm trying to adapt what I know to MX and its tough. :smashpc:

I have 2 springs I'm going to try tomorrow, both progressive, I'm hoping to see if there is a difference on MY bike vs running on someone else's.

  • farfromhome63

Posted 22 September 2011 - 05:25 AM

#10

Tye I bet your issue lies in the rebound circuit, my suspension guy softened the rebound stack because I was using the stock spring. The clickers didnt have enough range. You might try getting it re valved by a reputable ktm shop they might have some insight. Traction shouldn't be an issue and that rebound circuit not being optimal exacerbates that.

  • tye1138

Posted 22 September 2011 - 08:32 AM

#11

Tye I bet your issue lies in the rebound circuit, my suspension guy softened the rebound stack because I was using the stock spring. The clickers didnt have enough range. You might try getting it re valved by a reputable ktm shop they might have some insight. Traction shouldn't be an issue and that rebound circuit not being optimal exacerbates that.


Yep, its been re-built by Zracing, our local KTM shop. The rebound stack and adjustment is excellent. Though you are completely accurate in rebound being an issue, the shock stock was completely useless in that department both adjustment wise and functionality on track.

  • Bryan Bosch

Posted 22 September 2011 - 08:34 AM

#12

i've ridden both a lot. No difference that i can tell....


+1 :smashpc: But, I'm not Ricky Carmichael either.

  • Adammoto

Posted 22 September 2011 - 08:44 AM

#13

+1 :smashpc: But, I'm not Ricky Carmichael either.


I'm not Carmichael either, but for me the difference between my 2011 PDS and the 2012 linked chassis was night and day.

  • kan3

Posted 22 September 2011 - 09:10 AM

#14

Tye I've got to slightly disagree on this, I realize you have two bikes setup the same, remember when you change springs you also need to adjust the rebound


If you have to revalve a shock to compensate for a spring change then there is a difference. To further support this conclusion, the majority don't revalve their suspension so for those that do infact change their spring there is a difference.

  • MrBlahh

Posted 22 September 2011 - 09:14 AM

#15

You really shouldn't throw on a progressive spring without changing the valving to match

I prefer a progressive spring setup

  • Bryan Bosch

Posted 22 September 2011 - 11:30 AM

#16

I'm not Carmichael either, but for me the difference between my 2011 PDS and the 2012 linked chassis was night and day.


But, to be fair, I have a full revalve and progressive spring by Stillwell Performance. Regardless, I've just never been too picky about variables from bike to bike. Some things are better, some are worse. I just adapt to them quickly.

  • tye1138

Posted 22 September 2011 - 07:42 PM

#17

Ok, so 6.0kg stock progressive spring today and man what a difference. It sucks that the shock will need to be re-valved, but ohh well... gives me a chance to throw in the race tech bladder I bought. Needless to say it was a distinct improvement over the straight rate spring, of the same rate.

Also, its still doesn't feel like a linked rear end. I can't wait to get the 2012 250SX, thats my next bike and do an A/B comparison. Having owned a linked rear end 2 stroke and having ridden many more, my comment early still stands, PDS linkless is a pain in the butt to deal with, I can't wait to get back to a linked rear end.

  • mog

Posted 23 September 2011 - 01:06 PM

#18

you can feel a difference is ride height from a linear to a progressive spring with the Same sag settings , they do feel different , you would not expect them to feel the same ?

a well setup pds feels like a linkage bike , a badly setup pds feels scary

  • tye1138

Posted 23 September 2011 - 08:35 PM

#19

a well setup pds feels like a linkage bike , a badly setup pds feels scary


And PDS is a pain to setup right, as I've found out the hard way.

Honestly, I'm more happy with the rear now then I've ever been, but its still nowhere near the grip levels of a Japanese linked rear end of my old KX125.

  • GDI70

Posted 24 September 2011 - 07:10 AM

#20

+1 :thumbsup: But, I'm not Ricky Carmichael either.


reb clicker all the way in, and barely any preload on the spring to get 120mm of sag! :smashpc:
i think that's how his kawi was set up.

my friend has been on katooms for over 8 years. he only rides the straight-rate springs and he's a serious off-roader.
i asked him why he didn't care for the progressive spring. for him, it was a feedback issue. he liked the way the sr spring felt in cornering. he didn't care for the braking bumps, all the time, but overall he felt the sr spring turned better, and worked well for seat-bouncing obsticles. he rides the longer enduro style races.





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