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Convert WP Closed Chamber Bladder Forks to a KYB/Showa style Spring ICS internal cartridge - WP Race Performance Fork Kit (Collective Tuning)

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I've created this thread for converting WP CC "internal bladder" forks (Not 4CS) to KYB/Showa "spring style" ICS internal cartridges. WP now offers the WP Race Performance Fork Kit (Part number: 48601441s) which can be purchased from PG Suspension and other WP suspension dealers. The cost of these new kits is somewhere in the neighborhood of $1100+.

 

Qualify this thread: First let me qualify my point of view on this topic by stating that I am not an engineer or a suspension expert by any means. I am simply a MX enthusiast with basic/intermediate experience and skills in suspension tuning for KYB and WP forks. My depth of tuning ranges from typical oil, spring, and seal changes up-to refreshing OEM components on my WP CC bladder style forks. I am very meticulous in my approach, but I generally only follow best practices from suspension experts. I have not dived into more advanced modifications such as re-valving or modifying shim stacks. As an owner of two 2011 KTM's (150 & 250sx) with CC bladder forks and having ridden approx. 175 hours between both bikes, I feel it's a good depth of experience to compare the forks before and after the conversion.

 

The Problem as I see it: It's well known that KTM's with WP Closed Chamber Bladder forks are not designed to be speed sensitive (different rates of speed in which the forks compress), therefore creating what many people and magazine testers have referred to as mid-stroke harshness. While the CC Bladder forks seem to perform well in "full stroke" or heavy compression scenarios, their performance is very sub-par and uncomfortable in lighter scenarios where only partial to mid-stroke compression occurs...compared to the Japanese suspension manufacturers. The typical scenarios for noticing the harshness of the WP CC bladder forks are whenever you encounter smaller style chatter or acceleration bumps, or generally whenever the forks need to compress at a fast rate of speed but without enough force/weight to be compressed more fully. While mid-stroke harshness is often referenced, I like to think of it as initial stroke harshness and/or "slap rebound" as the sensation experienced feels like your hands are being slapped. I find the slap is more clearly noticeable on lighter bikes while heavier 4 strokes give the sensation of a more mid-stroke harshness. 

 

The Theory: In overall design, the WP forks are very similar to Kayaba forks with the exception that WP chose to use a air bladder style cartridge instead of a spring-based system. The new WP Race Performance Kit is a direct replacement of the air bladder for a spring style system (see attachment). In theory, this should allow the initial movement of the fork to be more "speed sensitive" as the movement of oil pushing on the spring and valving should be more linear or progressive. On lighter faster hits, the air bladder simply doesn't react fast enough or and even prevents the initial compression stroke from being smooth and linear.

 

The Goal of this thread: I have ordered a WP Race Performance Fork Kit and will seek to fine-tune forks on my 2011 250sx initially and then on my 150sx later on. I fellow friend has ordered the Kit for installation on a 2014 350sx-f. While the Kit is expected to be a direct replacement, it's highly likely additional tuning to maximize performance will be found by other early adopters of this kit. As more knowledge is gained we hope you will share your experiences in this thread so that we will hopefully resolve our woe's with WP CC Forks.

 

My plan is to install the kit on my 250sx over the next couple of weeks, begin riding and then note my findings. I hope others will do the same.

ICS.png

Edited by tk2stroke
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I'm running KYB SSS carts in my wp fork tubes. Absolutely love em.

Corey at protune suspension does this swap for half what that kit costs and that includes a revalve. If you're the DIYer like myself then you can purchase the parts and make the swap yourself with a little machine work.

Still interested in where this thread goes. I'll be monitoring :)

Edited by Dadee
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I'm running KYB SSS carts in my wp fork tubes. Absolutely love em.

Corey at protune suspension does this swap for half what that kit costs and that includes a revalve. If you're the DIYer like myself then you can purchase the parts and make the swap yourself with a little machine work.

Still interested in where this thread goes. I'll be monitoring :)

 

Do you have any documentation on the SSS conversion? I would love to explore that option as well.

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Well, neither the SSS ICS Design nor the WP bladder design is "speed sensitive". Both are spring elements and therefor both are position sensitive.

 

I'm not so sure if you are 100% right with your problem analyses but I'm really looking forward to your report after the installation!

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I've done the sss conversion and it works very well , I have just done a psf swap using the full psf fork

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Do you have any documentation on the SSS conversion? I would love to explore that option as well.

 

This was my reply from a user on KTMTalk asking some questions about it. These are the basics here.

 

1. Match the rebound adjuster to the WP one. You will probably have to machine down some on it to match the OD of the lock nut as well to keep the cart from bottoming on the adjuster.

2. Shorten the locknut to allow the bottoming cone to do its job. If you dont the cart will bottom on the locknut before the bottoming cone even engages.

3. I used the WP spring perch. If you take 2 of the collars and stack them on top of the WP spring perch it will mate up to the WP springs perfectly. At least it did on the 08 carts. You will have to machine out less than 1mm from the ID of the spring perch.

4. Turn down the top of the cart to match the OD of the WP tubes so it slides into your triples.

Thats for the most part all I did to make mine work. I bought the 08yz carts directly from Corey and he said those are the easiest to use for the swap other than the CRF carts. I would call him and ask him how difficult the swap would be. Even though hes running a business he was more than happy to help me out.

 

 

Also be sure to read these thread THROUGHLY

 

http://www.ktmtalk.com/showthread.php?t=489980

 

http://www.ktmtalk.com/showthread.php?t=499306

 

 

I wouldnt hesitate to give Corey a call with your questions after you school yourself up on the swap. Its really not that hard. Just takes time, patience and some mechanical know-how.

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I didn't do anything to the locknut ,it's the original one for the cart so can't see the problem ,a lot of carts don't need the top tubes modifying ,my 11 450 ones didn't but are 10mm too long

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Here are the psf fitted 2 spacers made and modified brake hanger and shim stock to space the lower triple clamp as the kyb is 1mm smaller od

1425498660205.jpg

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I didn't do anything to the locknut ,it's the original one for the cart so can't see the problem ,a lot of carts don't need the top tubes modifying ,my 11 450 ones didn't but are 10mm too long

Depending on which SSS carts you got they need more or less modification. I needed to shorten mine to get full travel out of the fork. I also needed to turn down the top of the carts slightly. Otherwise they were wider than the outer tubes and wouldn't slide through the triples very easy. Corey knows the ins and outs.

Also you need to use the WP oil lock collar.

Edited by Dadee

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No you can use the kyb oil locks and the kyb spring seats if you want ,with my shortened carts the kyb spring seats fitted perfectly with the std wp springs

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Mog, you can't always use the kyb locks the newer ones are too big. Most of them measure 27.9 and those are fine but there's a lot of them that are too big.

And regarding spring seats, there's two reasons I use the wp. One, most generally my customers won't need to purchase new springs. Second, I like the feeling of the higher perch being away from the oil.

And the locknuts always need to be shortened if you want all of the travel back. If you don't shorten the locknut the locknut will bottom before the full travel is reached. Some conversions this can be 3-5mm and some are closer to 10mm and in those situations you can part 7mm or so off the lock nut and then gain more if you continue the locknut dimension into the rebound adjuster.

When I'm done with a conversion the fork is the same length as a wp cc and has anywhere from 298-300mm of travel.

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I have 2 new tidbits of information to add to my original post...

  1. MXA has the WP Performance Kit published in this month's issue. I'm hoping they will test the product as well.
  2. MXA tested the Ride JBI Pro Perch as well with a pretty positive review.

In addition to installing the WP Kit, I'm going to splurge and purchase the JBI Pro Perch as well. I intend to install both components separately, the kit in the 250sx and the JBI Pro Perch in the 150sx. This was I can evaluate each component individually with the ultimate goal to then install both components together with the hopes of achieving the ultimate WP Closed Chamber fork. I'm excited to see how this all works out. 

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IMG_2211.JPG

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This was my reply from a user on KTMTalk asking some questions about it. These are the basics here.

 

1. Match the rebound adjuster to the WP one. You will probably have to machine down some on it to match the OD of the lock nut as well to keep the cart from bottoming on the adjuster.

2. Shorten the locknut to allow the bottoming cone to do its job. If you dont the cart will bottom on the locknut before the bottoming cone even engages.

3. I used the WP spring perch. If you take 2 of the collars and stack them on top of the WP spring perch it will mate up to the WP springs perfectly. At least it did on the 08 carts. You will have to machine out less than 1mm from the ID of the spring perch.

4. Turn down the top of the cart to match the OD of the WP tubes so it slides into your triples.

Thats for the most part all I did to make mine work. I bought the 08yz carts directly from Corey and he said those are the easiest to use for the swap other than the CRF carts. I would call him and ask him how difficult the swap would be. Even though hes running a business he was more than happy to help me out.

 

 

While the engineering hack can be appreciated, I'm inclined to pursue the WP Performance Kit now that a viable alternative may very well exist. If I were to consider going with a Kayaba SSS system, installing the entire SSS fork would be a more appealing route in my view to ensure all the benefits of the SSS suspenders would be realized.

IMG_2209.JPG

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The only benefit is the kyb uses a 15mm bushing vs a 12mm wp bushing in the outer tube.

But modern wp tubes are damn good so we're splitting very, very fine hairs here.

My kit is a drop in kit for any wp cc fork and I can also do the swap on most 4cs forks and all open chamber forks.

No aspect of the kyb design is changed. I don't even drill the floating pistons. I make sure the reservoir seal and orings are new.

And if you run the complete fork you're instantly running into brake, wheel, and offset issues.

I'm sure the wp kit will feel better than the bladder but the kyb mid and base pistons are damn good.

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Good stuff Corey I know mine gets to within 3 mm of bottoming so something must be close ,I shortened my cart by 10mm so maybe that's why ,I didn't realise kyb has different size cones

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my "good" 2009 KX450F forks had 28mm locks, my "cheap" 2012 forks have 29mm locks (cone ID 29.4mm)

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The ones I had were 0.1mm biggest than the wp ,I got lucky on that but didn't on the cart length ,that was a major pain

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It's weird to want to ditch the bladder

Is it just that they build up pressure by oil migration if you don't bottom them

Mxtech even sells an 800$ setup to make kyb forks bladder forks

I heard it's really good

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Update: The first known installation of a WP Performance Kit is complete on my buddies 350sx-f (photos attached). PG Suspension installed his kit along with re-valving the forms to go along with the new component. PD Suspension is said to have worked with WP during the development phase of the kit and apparently have come up with valving settings that complement the new hardware.

 

A report after the first ride will be forthcoming my either myself or RC268

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Edited by tk2stroke
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