Polaris XPT Shock Valving

Discussion in 'UTV Chassis & Suspension' started by Glamisfan, Mar 8, 2017.

  1. Glamisfan

    Glamisfan Active Member

    Joined:
    Oct 26, 2009
    Location:
    imperial valley
    Does anyone have a shock valving recipe to share? I have a two-seat XP turbo. It has the fox internal bypass shocks. Stock, there's 24 clicks of compression adjustable total, I had the front shocks 21 clicks in and the rear shocks all the way out at zero. I found the front springs to be way too soft and the rear springs to be too stiff. So with the compression adjusted that way the car seemed to ride fairly well. I just installed the shock therapy 3+ spring kit, which consists of four new front springs and the crossover, and two new upper rear springs with the crossover. I've only had it out for about an hour drive and it's much much improved. I'm trying it with 0-6 clicks in to start with. I also adjusted the crossovers up from the recommendations because it was still too firm.

    I've re-valved my own shocks on my super duty, they're bypass shocks. I've also set up the suspension on a race rhino that I built and a pre-runner. So I know how to do shock work. But, these internal bypass shocks are a little more complicated.

    I've heard over and over that shock therapy can do wonders with them, but I really don't want to spend $750 for something I can do my self for probably $40 in shims. I have not contacted pound sand to see what his prices are. And there's a couple of guys local to me that supposedly can we do them for $260 or something, but again, that's more than $40. And I would really like to do them myself.

    I think what needs to be done is drill the bypass ports out a little bit to give a smoother ride at slow speed and washboards, and make the valving a little stiffer so you have a better bump zone. Also, maybe put a flutter stack in, and maybe just in the rear only?

    Below are a couple of pictures of the Manual showing the shock specs, and that translated to the fox valving chart shows the rear at a 90 pound compression, and 80 pound rebound. It puts the front at 90 pound compression and 70 pound rebound. Buy pound, I'm referring to the # number in the fox valving chart.
    [​IMG][​IMG][​IMG]
     
  2. Rynomx785

    Rynomx785 Active Member

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    Wickenburg, AZ
    Following. I will be surprised if you find anyone that actually knows what they are talking about that is willing to talk shop with you.
     
  3. Rynomx785

    Rynomx785 Active Member

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    Wickenburg, AZ
    On a side note, Fox only runs the nitrogen at 75 PSI? Is the required pressure lower with an internal bypass shock or something? I have always heard 150-200 PSI depending on which shock company it is. Walker recommends 185 PSI.
     
  4. the stripping shop

    the stripping shop RACER - UTVUnderground Approved

    Joined:
    Jan 29, 2009
    Location:
    peoria,Az
    first off I have a couple of the fox shocks super low on nitrogen, stupid needle valve.2nd you need some speciality tools from fox to take them apart and fox has them been on back order for the last 2 months. Everything you said to do is everything I have tried and a combo of that works very good for my style of riding. Change reservoirs to Schrader valves first and your shock will change drastically then make the valving changes.
     
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  5. Glamisfan

    Glamisfan Active Member

    Joined:
    Oct 26, 2009
    Location:
    imperial valley
    I just read about the reasoning for the low nitrogen pressure somewhere, but I forget exactly what it was. I do remember something about it given a smoother ride over washboard. I bought the needle fill adapter for my Schrader setup, but I sure don't like it! So I will be converting it to a Schrader setup.
     
  6. BiggJim

    BiggJim I Hate Rules - UTVUnderground Approved

    Joined:
    Jan 15, 2009
    Location:
    Bakersfield
    We have schrader set ups instock as well as dsc's, spring packages, and billet negative spring guides.
     
  7. Glamisfan

    Glamisfan Active Member

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    But no valving packages for the Diy'er???
     
  8. BiggJim

    BiggJim I Hate Rules - UTVUnderground Approved

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    We havent put a huge effort is to valve codes for a stock width car yet. Only Long travel.
     
  9. Glamisfan

    Glamisfan Active Member

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    That makes sense. Got any pointers on what you would do to the stock shocks if your own play car? Please!!!!!
     
  10. george.felix

    george.felix George

    Joined:
    Jan 11, 2015
    Location:
    Houston, Texas
    I'm no expert but i believe the first thing to do is get the right springs and set ride height. Remember I said I don't know anything but I'd set preload to 1/4" in the rear and see where that puts the height. I'm guessing your liking for 13.5-14.5. If it's taller than that springs too firm. Less and you can add preload. Then set the front. Adjust the preload till you get where u want it with front 1/2-1" taller than rear.

    Jim, isn't that close to a starting point? I know valving was the question but springs then valves right?
    On stock 2 seat the first thing Fox did was slow the front rebound down quite a bit like a couple steps whatever that means. I don't have the valving notes because they lost them. Johnny and Dan were there so who cares about stock travel car..... :) I may have something on a napkin covered in mustard the dog half ate....maybe.
     
  11. the stripping shop

    the stripping shop RACER - UTVUnderground Approved

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    I wish you had put on your website that you have any of this stuff. I will be calling
     
  12. Glamisfan

    Glamisfan Active Member

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    Oct 26, 2009
    Location:
    imperial valley
    I've had two shock tuners tell me that the compression adjuster needs to be opened up and revalved too. It just keeps getting more complicated! One also said they put in a higher flowing piston. Makes me consider selling these and going to a coil over/bypass setup! That I can handle myself!

    The car works great with just the spring change. So I need to get a ride in one with ST's full setup, and then decide if I want/need to have them revalved.
     
  13. Rynomx785

    Rynomx785 Active Member

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    Jun 21, 2015
    Location:
    Wickenburg, AZ
    I have heard the same thing about "high flow pistons" too. I am not a shock expert or tuner but a high flow piston doesn't make sense to me. The ports in a piston are huge and the oil flow is controlled with a shim stack. I have heard that chamfering the edge of the port holes in the piston can help smooth out the oil flow but that is pretty simple stuff. I have to wonder if the "machining" some companies claim to do on pistons is simply adding free bleed ports? I don't know anything about the IB Fox Shocks but I know that the rear pistons on the XP 1000 have free bleed ports stock and the front does not.
     
  14. Glamisfan

    Glamisfan Active Member

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    Oct 26, 2009
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  15. Glamisfan

    Glamisfan Active Member

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    I was reading through my notes and found this. It really explains it:

    . As with a regular external bypass shocks, there is no cavitation in the compression stroke due to the inner cylinder being capped off from shock oil flow to reservoir area. Base valves can be fitted to this inner cylinder design so that if any cavitation is occurring during the rebound cycle it can be eliminated. This also allows for very low reservoir nitrogen gas pressures to be used that will reduce seal wear as well as let the shock shaft move very easily at low shaft speeds, giving a little more comfortable ride over the small rocks.
     
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  16. Rynomx785

    Rynomx785 Active Member

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    Interesting. Thanks for sharing.
     
  17. Rynomx785

    Rynomx785 Active Member

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    How will just changing from the needle valves to schraeder valves change the shocks drastically? How will it change them exactly?
     
  18. Glamisfan

    Glamisfan Active Member

    Joined:
    Oct 26, 2009
    Location:
    imperial valley
    So I think I’m going to go ahead and just do the compression on the rear myself. With shock therapy springs the shocks work really good now, except the rear is a little too stiff still.

    Below is a picture showing the stock rear compression stack, below that is the standard fox chart sizes, which if you’ll notice there standard chart does not use the 1.250 and also has a .80 on the bottom instead of a .90. On the right is what I think I’m going to try first. The stock stack has a 1.8 x .006 shim that has four cut outs to act as a free bleed. Since other fox shocks don’t use that I figure I’ll get rid of that, because even though it has the cut outs for free bleed, it’s still making the 1.8 x .015 act like it’s even thicker, and then do the first two largest shims with the .012 shims and I’m thinking about getting rid of the .900 on the bottom which would make the .950 the pivot point effectively stiffening up the high-speed a little bit I think[​IMG]
     
  19. Glamisfan

    Glamisfan Active Member

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    Oct 26, 2009
    Location:
    imperial valley
    I changed the rear rebound to 1.6x.010, then .012 on the rest. Left the compression alone, except I removed the middle shim from the lower bypass port. I’ve only had it out for 20 minutes, but it’s much improved. I’ll probably revalve it one more time. Here’s a vid of the internals.
     
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  20. Glamisfan

    Glamisfan Active Member

    Joined:
    Oct 26, 2009
    Location:
    imperial valley
    1/14/17
    I revalved the rear shocks a second time. Rebound is
    1.6x.010
    1.425x.010
    1.35x.010
    1.1x.010
    .950x.010
    .800x.020
    .800x.020
    .800x.020

    I also replaced the 1.8x.015 compression shim with a .012 and cut down two of the bypass check valves.

    The car works extremely well now. It’s just a hair light on rebound at slow speeds, but works well at 40+ mph. There is no donkey kick. It handles 1.5 foot whoops at 60-70 mph.

    I’m happy with rear shocks now, and the stock fronts so far seem good to me. I have the rear clicker all the way out (full soft), and I started with the fronts at 15 in, then backed out to 12 in, then went down to 10 in. I still haven’t ran it against a full ST car yet, but I’d like to, and video them so I can see how they compare.

    You can see what I cut on the bypass check plates below.
    [​IMG][​IMG]
     

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