KTM PDS shock question

[Atcr1]

So I ride a 2009 KTM 530 XC-W. I am in the process of upgrading the rear shock. I purchased a progressive rate spring from Slaven racing (the stock spring is a straight rate) and was going to have my local suspension shop here in Phoenix revalve the rear for a progressive spring. The shop is Futureshoxs and owner has been racing and working on suspensions for over 20 years, specifically KTM's so I would like to think he knows what he's doing. He said unless I really need to that the rear shock is already progressive hence the PDS. This is what i originally thought, since its a linkless system. But 2 of my local KTM shops are saying that the shock must be revalved as progressive to accomodate the progressive spring??? Any thoughts or has anyone upgraded to progressive springs without revalving on the PDS system? thanks.

[mog]

you don't have to revalve the shock for a different spring , but with a PDs I think it's always wise to get a package setup , don't try to mix and match setups

[Adammoto]

There is no specific damping setup required to run a progressive spring. You can add bottoming resistance to PDS, if it is needed, with a progressive spring or progressive damping force, or both. With the progressive spring you may be able to get away with lighter valving on the secondary piston...which may be a good thing...but it is by no means "required."

[Atcr1]

Thanks everyone for the info. I will just instal the spring and start there.

[motoXr_22]

when I put a race tech P10 spring on my rear shock on my 250sxf it originally had a 6.9kg straight rate but with the stock valving it was pretty crap just kicked around off bumps/holes etc so I think a re valve is needed

[Atcr1]

Just an update: this spring rocks!! It is so much better than my buddys Racetech spring. The Slaven ones are wound at a different rate and they work. First ride, dialed in the sag and hit the fast rocky stuff. Instant improvment, I didn't need to revalve and never even messed wit the clickers, I just left them as they were from the previous spring. Second ride loaded up about 30lbs of camping stuff, reset the preload and sag for the increased weight, and again outstanding performance. Only downside is now I need to do the front shocks. I'm noticing the front dive more under breaking now that the back is riding like it should.

[Dwight_Rudder]

I strongly suggest that you DON'T run a progressive spring. They require too much preload to work properly. I tried them and quickly went back to straight rate springs. I did have to go up a couple spring rates to get the correct 38mm static sag and 114mm rider sag, that I was looking for. Once I had the correct spring the rear felt very progressive due to the low preload rate. Very plush. As good as any Honda that I have ridden.

[mog]

Seems a little redundant to tell him not to run a spring he currently feels is working extremely well?

[Dwight_Rudder]

Seems a little redundant to tell him not to run a spring he currently feels is working extremely well?

He will find that he will like it a lot better when he has the correct spring. Some don't know how good it can be.

[Adammoto]

Just an update: this spring rocks!! It is so much better than my buddys Racetech spring. The Slaven ones are wound at a different rate and they work. First ride, dialed in the sag and hit the fast rocky stuff. Instant improvment, I didn't need to revalve and never even messed wit the clickers, I just left them as they were from the previous spring. Second ride loaded up about 30lbs of camping stuff, reset the preload and sag for the increased weight, and again outstanding performance. Only downside is now I need to do the front shocks. I'm noticing the front dive more under breaking now that the back is riding like it should.

Glad to hear the spring worked out.

With a topic as personal as suspension, many a dead horse has been beaten. Setup preferences are hugely dependent on riding style and terrain -- always trust your own experience!

[Dwight_Rudder]

If you are running too much preload then you will overload the front suspension.

"You can lead a Horse to water but you can't make him drink" So he dies of thirst ........................LOL.

[Sun Devil]

I strongly suggest that you DON'T run a progressive spring. They require too much preload to work properly. I tried them and quickly went back to straight rate springs. I did have to go up a couple spring rates to get the correct 38mm static sag and 114mm rider sag, that I was looking for. Once I had the correct spring the rear felt very progressive due to the low preload rate. Very plush. As good as any Honda that I have ridden.

Dwight,

Running too much preload on any spring will cause the suspension to work poorly. Can you mechanically explain why a progressive spring will not work for a PDS shock, beyond your own personal experience that it did not work well for you? Just curious, as PDS shocks are not my strong point.

[Atcr1]

actually I'm running less preload than the same shock with a straight rate spring. I've heard nothing but good things from all the big suspension guru's about running newer progressive springs for desert riding. I'm glad I listened because I'm sold.

[TmanTman]

I spend half my dirt bike surfing time on KTM talk and half on Thumper talk. Both are good sources of information. KTM talk has weird banning policies; however, I must admit that the suspension forum here is mind boggling because there is no consistency between the assigned expert and other riders that offer an opinion.

[Dwight_Rudder]

Dwight,

Running too much preload on any spring will cause the suspension to work poorly. Can you mechanically explain why a progressive spring will not work for a PDS shock, beyond your own personal experience that it did not work well for you? Just curious, as PDS shocks are not my strong point.

To get the suspension to work properly with a progressive spring you have to run a very very heavy spring. With the proper straight rate spring you can have as little as 3mm of preload on the spring. You want 5mm or less. You have trouble getting that with a progressive spring. So you get a harsher ride over the small choppy bumps , square edged holes, roots and rocks. It is important on a PDS to have that minimal preload and have the needed 114mm (+-2mm) rider sag, to get a very plush and controled ride that "Feels" progressive. With the minimal preload the spring can react quicker and with the straight rate it can firm up as nessesary. All, I can say is try it and see. You will be pleasantly surprised at how nice a non linkage suspension can be.

[Sun Devil]

To get the suspension to work properly with a progressive spring you have to run a very very heavy spring. With the proper straight rate spring you can have as little as 3mm of preload on the spring. You want 5mm or less. You have trouble getting that with a progressive spring. So you get a harsher ride over the small choppy bumps , square edged holes, roots and rocks. It is important on a PDS to have that minimal preload and have the needed 114mm (+-2mm) rider sag, to get a very plush and controled ride that "Feels" progressive. With the minimal preload the spring can react quicker and with the straight rate it can firm up as nessesary. All, I can say is try it and see. You will be pleasantly surprised at how nice a non linkage suspension can be.

Thanks and interesting. How can a straight rate spring feel more progressive over an actual progressive spring? Mechanically that is impossible. The progressive feel of the shock comes from the angle it is mounted and the configuration of the dual pistons and shock needle. Logically I would believe that a progressive spring paired with a PDS shock would increase the progressive feel.

[mog]

I have ridden pds with straight and progressives springs and both with the correct rate work well , with compromises on both setups ( trades) I don't think we can label all progressives bad, but the straight are easier to setup Imo

[Dwight_Rudder]

Thanks and interesting. How can a straight rate spring feel more progressive over an actual progressive spring? Mechanically that is impossible. The progressive feel of the shock comes from the angle it is mounted and the configuration of the dual pistons and shock needle. Logically I would believe that a progressive spring paired with a PDS shock would increase the progressive feel.

The progressive feel comes from the low preload and the rate increases with compression. Not hard to understand. The angle effects the leverage ratio, another reason that a straight rate works so well.

[kimberley rider]

have to agree with Dwight I always use very little preload on all my katos , it gives you good and easy bike control with the altering of body position , the back moves easier so for high speed stuff and the bike angles back and rides over the snotty stuff. For tight and twisty its plusher when you are on the tank, get the spring right and work out your rebound dampening less is better and you will be amazed how the front end feels better because the bike has a better usable balance

[mog]

If you get a progressive that starts at a similar rate to the straight then increases to a higher end point, you will get it to hold up in the stroke well, you will have to compensate with a softer hs stack and possibly needle overlap

To think only straight rates work for all types of riding is very narrow minded? Its saying no tuners can make a pds work unless they use a straight spring, therefore disrecpecting the work of any tuner that has aldready done so?

That's like a jap bike rider saying no pds works as I have trieda few and I didn't like it, so its impossible and I know best

If you get a progressive that starts at a similar rate to the straight then increases to a higher end point, you will get it to hold up in the stroke well, you will have to compensate with a softer hs stack and possibly needle overlap

To think only straight rates work for all types of riding is very narrow minded? Its saying no tuners can make a pds work unless they use a straight spring, therefore disrecpecting the work of any tuner that has aldready done so?

That's like a jap bike rider saying no pds works as I have trieda few and I didn't like it, so its impossible and I know best

Good enough to say twice!