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  1. #1
    mtbr member
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    Curnutt Air vs Coil

    I'm getting ready to pull the trigger on an XCT 5. But before I do I want to make sure I'm getting the right shock. I'm leaning toward the coil w/ steel spring because I'm not worried about weight and have read that the coil is more adjustable which I prefer. But want to see if anyone might be able to provide some comparisons/contrasts between the Curnutt air and coil shock.

    Any input would be greatly appreciated!

  2. #2
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    From my experience the coil isn't as adjustable as you think.
    Due to the 2.1 ratio, the spring size difference of 50lbs is way to big. Work out the maths, if a std 3:1 shock has springs at 50lb intervals, the 2:1 ratio needs a smaller step between sizes.

    Go for the Air, that way you can dial the sag in as you want rather than what the springs dictate.

    For example, I had a 300 supplied with the FXR, too firm. I then got hold of a 250, too soft. A 275 would have been spot on.

  3. #3
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    Customized

    three things I've learned;
    1) At 200 lbs Foes discouraged me from buying the air shock for the FXR, so ask them 1st.
    2)If you want it to be plush tell them before you buy and, like mine, they can do at least 4 different things to make it more plush; night and day difference.
    3) Foes' weight chart for the spring rate had my 200 lb weight on the border between 300lb and 350 lb coil, when I sent my shock in for the rebuild with the unmarked coil they tested it and found it to be a 250 lb and said there wasn't evidence of excessive bottoming so they advised me to keep the lighter coil, so if you want it plush ask them about a lighter coil. Like nz162 said the 50 lb spread in spring weight has a bigger effect on a 2:1 leverage bike, fortunatley if you go with a lighter spring you can overcome the issue by increasing pressure or dialing in the bottom out ramp on one end, or increasing the Curnutt valve pressure on the starting end, or both, infinite adjustment if you take the time. Go slow, small adjustments make a noticable difference so do your base tuning at a section of trail that will allow you to repeat the test with every adjustment.
    When I bought the bike (used) it was snapier than my 5" Turner, but the ride was harsh on ripples and the "bump" through the frame from the valve opening was annoying. The bike is now very plush on all size bumps and while you can hear the valve opening the "bump" through the frame is gone, while not quite as snapy, it still rewards aggressive pedaling but is slightly more slugish on long intermediat climbs
    Last edited by slowrider; 01-27-2009 at 10:14 AM.

  4. #4
    Elitest thrill junkie
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    Quote Originally Posted by slowrider
    fortunatley if you go with a lighter spring you can overcome the issue by increasing pressure or dialing in the bottom out ramp on one end, or increasing the Curnutt valve pressure on the starting end, or both, infinite adjustment if you take the time.
    True, but should point out that it's not optimal and it adds more compression damping than is necessary for the absolute best performance. Best is to get the right spring, then set the damping, but barring that air could be the way to go. I'm in between spring sizes on my avalanche shock and looking for the right spring right now, it doesn't matter what coil shock you're talking about though, the correct spring rate is better and foes really should offer springs in 25 or 15lb incriments for their 2:1 leverage.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  5. #5
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    Cool...thanks for all the feedback

    Quote Originally Posted by slowrider
    1) At 200 lbs Foes discouraged me from buying the air shock for the FXR, so ask them 1st.
    Wonder why Foes discouraged you against the air shock because of your weight? I weigh @ 200 lbs as well so looks more and more like coil is the way to go.

    And as far as what has been said here and in several other threads about the Curnutt being harsh or rough, I'm not worried. I currently own a Spec Epic set up about as firm as I could get it, both front and rear, for racing and I use it as my everyday bike too since it's my only bike. So every other FS should feel like a Cadillac compared to my Epic. I may decide to move down to a 250lb spring but to start I think I'll try a 300lb spring or what Foes recommends on the XCT 5 based on my weight.

    OK I know that Ti is a superior mat'l choice for suspension springs...but not for my wallet. But I would seriously consider buying one instead of the steel spring if there is a vast improvement in performance.

    Has anyone ridden both the steel and Ti springs and if so how do they compare?

    Again thanks for the info

  6. #6
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    Cheaper option

    As stated I like my Curnutt now but you could save considerable weight and money by ordering your XCT5 with a DHX Air, I tried to buy one for my 06 fxr but the Foes adaptor makes the DHX 1" too long.

  7. #7
    mtbr member
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    Some info I found on Ti vs. steel springs...

    http://www.coilspring.com/performance/why_titanium/

    http://www.coilspring.com/performanc..._titanium.html

    http://www.coilspring.com/performanc..._vs_steel.html

    And Brett Foes interview below. It's 9 min long and he talks about the Curnutt shock specifics @ 6:45 min into the vid.

    http://www.youtube.com/watch?v=nZHXCm4pdFY

    So the XCT-5 is on order. Should arrive in a couple weeks and probably be at least a month before I complete the build and hit the trails. I'll post some pics and my opinion on the bike after some serious play time. As far as the shock I selected...you'll just have to wait and see...

  8. #8
    AnnaZed
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    sgill32, you should contact us at Foes about this.

  9. #9
    Crazed Country Rebel
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    Quote Originally Posted by sgill32
    I'm getting ready to pull the trigger on an XCT 5. But before I do I want to make sure I'm getting the right shock. I'm leaning toward the coil w/ steel spring because I'm not worried about weight and have read that the coil is more adjustable which I prefer. But want to see if anyone might be able to provide some comparisons/contrasts between the Curnutt air and coil shock.

    Any input would be greatly appreciated!
    You should get the air shock. It's much more adjustable - without the added cost of buying multiple springs, should you not get it right the first time.

    With the 2:1 leverage ratio, your weight should not be a problem. You run far less air pressure in this shock then others. At 200 pounds you might need 110 psi in the shock.

    I currently own 2 Curnutt coil-equipped bikes and had the opportunity to do a long test ride on a Curnutt Air equipped bike this last weekend. The air shock rips! It doesn't bob, is super plush and just glued to the ground. I was impressed.
    Stupid, but sometimes witty. Occasionally brilliant. Slow and fat though.

    Specialized sucks dong

  10. #10
    mtbr member
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    Done Deal

    [SIZE="3"]I appreciate the advice but I went ahead and ordered the frame. It's absolutely amazing! I was going to hold off on pics until after the build but too excited to show it off. Don't know if you can tell in the pics but the orange is metallic and it looks really bad ass in the sun.[/SIZE]

    DSC00279.JPG

    LARGE FRAME -- Weighs just over 8lbs

    DSC00287.JPG

    DSC00289.JPG

    CURNUTT XTD W/ TI SPRING

    AnnaZed I'm sure you remember this one, picked it up thru Adrenaline Bikes (great guys BTW). Got it last week. And I really like the two bends in the top tube on the '09 vs the swooped top tube. Gives it a more aggressive look.

    So cat's out of the bag now as to the shock I selected. I went Ti coil over vs the air because I've always owned air shocks and I've always wanted a Foes with the coil shock. I actually have the bike completely built except for the rear brake. I was a knucklehead and ordered one with too short of a hose. But let me tell you this thing is so damn sweet looking. And I've taken it for a spin around my neighborhood jumping off curbs and stuff and really like how it feels so far. Nothing will compare to getting it out on the trail though...and I'm so excited I can't wait.

    I should get the new rear brake this week. I'll post some more pics along with build list when I get it all together.

  11. #11
    Crazed Country Rebel
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    Quote Originally Posted by sgill32
    [SIZE="3"]I appreciate the advice but I went ahead and ordered the frame. It's absolutely amazing! I was going to hold off on pics until after the build but too excited to show it off. Don't know if you can tell in the pics but the orange is metallic and it looks really bad ass in the sun.[/SIZE]

    DSC00279.JPG

    LARGE FRAME -- Weighs just over 8lbs

    DSC00287.JPG

    DSC00289.JPG

    CURNUTT XTD W/ TI SPRING

    AnnaZed I'm sure you remember this one, picked it up thru Adrenaline Bikes (great guys BTW). Got it last week. And I really like the two bends in the top tube on the '09 vs the swooped top tube. Gives it a more aggressive look.

    So cat's out of the bag now as to the shock I selected. I went Ti coil over vs the air because I've always owned air shocks and I've always wanted a Foes with the coil shock. I actually have the bike completely built except for the rear brake. I was a knucklehead and ordered one with too short of a hose. But let me tell you this thing is so damn sweet looking. And I've taken it for a spin around my neighborhood jumping off curbs and stuff and really like how it feels so far. Nothing will compare to getting it out on the trail though...and I'm so excited I can't wait.

    I should get the new rear brake this week. I'll post some more pics along with build list when I get it all together.
    NICE! Post build pics when you're done.
    Stupid, but sometimes witty. Occasionally brilliant. Slow and fat though.

    Specialized sucks dong

  12. #12
    AnnaZed
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    Ah yes, I know that frame. For those on the forum I don't know how to describe it, but that color is so much more dynamic than it looks in that photo. Please send me photos of your build.

  13. #13
    mtbr member
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    Ready to roll

    Build List:

    - 2009 Magura Thor 140mm Fork w/ Maxel 360
    - Formula Oro K24 Disc Brakes (180mm front/ 160mm rear disc)
    - FSA V Drive MegaExo Crank-Set
    - Shimano XTR Cassette
    - SRAM PC 991 Cross-step Chain
    - SRAM X7 Rear Derailleur
    - SRAM X9 Front Derailleur
    - SRAM X0 Grip Shifters
    - ODI Lock-On Grips
    - Spank Spike 777 Handle Bar
    - Nuke Proof Warhead 90mm Stem
    - Sunline V-One AM Headset
    - Thompson Elite Seat Post
    - WTB Pure V Race Saddle
    - Time XS Carbon Pedals
    - Spinergy Xyclone Wheels
    - WTB ExiWolf 2.3 Race Tires
    - Slime Tubes

    DSC00318.JPG

    DSC00312.JPG

    DSC00329.JPG

  14. #14
    Crazed Country Rebel
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    Quote Originally Posted by sgill32
    Build List:

    - 2009 Magura Thor 140mm Fork w/ Maxel 360
    - Formula Oro K24 Disc Brakes (180mm front/ 160mm rear disc)
    - FSA V Drive MegaExo Crank-Set
    - Shimano XTR Cassette
    - SRAM PC 991 Cross-step Chain
    - SRAM X7 Rear Derailleur
    - SRAM X9 Front Derailleur
    - SRAM X0 Grip Shifters
    - ODI Lock-On Grips
    - Spank Spike 777 Handle Bar
    - Nuke Proof Warhead 90mm Stem
    - Sunline V-One AM Headset
    - Thompson Elite Seat Post
    - WTB Pure V Race Saddle
    - Time XS Carbon Pedals
    - Spinergy Xyclone Wheels
    - WTB ExiWolf 2.3 Race Tires
    - Slime Tubes

    DSC00318.JPG

    DSC00312.JPG

    DSC00329.JPG
    Great looking bike! Can't wait to get my new fxr.
    Stupid, but sometimes witty. Occasionally brilliant. Slow and fat though.

    Specialized sucks dong

  15. #15
    mtbr member
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    Thanks. Looking forward to seeing some pics of your FXR!

  16. #16
    mtbr member
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    Upgraded already

    Decided to throw on a set of DT Swiss EX1750's and they belong on this bike. Should'a did this in the first place but the Xyclones are going to good use on my Epic.

    DSC00365.JPG

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    DSC00362.JPG

    DSC00359.JPG

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    I've only had the chance to ride it twice so far. Want to break it in good and do some serious riding on this bad mofo before I post any comments on how it performs. I will say this, the first two times out I was grinning from ear to ear. I'll post a review in a few months.

  17. #17
    AnnaZed
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    That thing is damn sexy, looks great.

  18. #18
    mtbr member
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    What is up with the long coller on the spring?

  19. #19
    mtbr member
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    Quote Originally Posted by kntr
    What is up with the long coller on the spring?
    My guess would be because the threads on the shock body probably don't go down far enough for a narrow collar like on the FXR.

  20. #20
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    Pics from 3 shocks fitting 2.1
    steel spring
    Ti springs (2 coils: 150 ounds then 250 & 350 pound springs)
    & the best one Air Schock
    Attached Images Attached Images

  21. #21
    gravity challenged
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    Little late here but I'm 240 and ride an XCT-5 with air shock. Works great everywhere, up, down, flat, smooth, bumpy, whatever. Tuning makes all the difference. It is entirely possibly to set the shock up incorrectly and completely eff it up. Set it up right and you will more than likely be a happy camper!

  22. #22
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    just to add that the clip on the blue reservoir is not put properly on my air shock picture. This wrong way did some clinc! clanc! STRANGE NOISE.
    I change it clipping the cylinder closer to the end or the black tape (left side) and air channel.

  23. #23
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    Quote Originally Posted by missfoesquebec
    just to add that the clip on the blue reservoir is not put properly on my air shock picture. This wrong way did some clinc! clanc! STRANGE NOISE.
    I change it clipping the cylinder closer to the end or the black tape (left side) and air channel.
    thats where the bracket is suppose to go. my Air on my RS7 was mounted at the base near the hose on the reservoir.


    man, i cant imagine the stiction that 4.5" stroke shock feels...my 3" stroke RS7 shock feels ridiculously sticky!

  24. #24
    gravity challenged
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    Quote Originally Posted by deadatbirth
    ...man, i cant imagine the stiction that 4.5" stroke shock feels...my 3" stroke RS7 shock feels ridiculously sticky!...
    Length of travel of the shock should not influence "stiction", all other things being set up correctly. A lower leverage ratio (eg 2:1 vs 3:1) means a longer travel shock for the same wheel travel, but also results in lower air pressures, and therefore lower seal tensions required to prevent leakage.


  25. #25
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    Hey SGill, I'm still waiting for your report on the ride! It's been five months! Spill it as I'm in the market for a FXR as well!!

    -Rob
    "No, you're going to be promoted to GLG-20."

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