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  1. #1
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    2009 Mach 4: upgrade to Fox Float CTD w/Boost Valve?

    I have a 2009 Mach 4 with original Fox RP23 shock. I'm wondering if it would be a worthwhile upgrade to get a new Fox CTD shock with or without Boost Valve? I love my Mach 4 as-is, but if I can make it even better, why not? Anyone out there that has done a similar upgrade of the rear shock? Pivot folks? Thanks!

  2. #2
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    My 2 Cents

    I have ridden the PM4 with and without the BV and do not think there is enough performance difference to justify the upgrade cost. In fact, I believe the non BV worked a little better. I remember reading that one of the reasons Pivot in 2011 switched to a shorter 1.75” stroke shock was to help make the BV more effective.

    If you are looking to upgrade there may be a slight performance gain from just replacing the older shock mounting hardware to the latest Fox offering:

    Mounting Hardware | New for 2013 | Bike | FOX

    If you do upgrade let us know your thoughts on if it was worth it.
    "If I should die darling in your arms, what a lovely way to go..." Don Felder -All of You

  3. #3
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    Thanks, Maluco. I certainly have no complaints about the current rear suspension performance. I'm curious more than anything. Hadn't heard about Fox's new mounting hardware. Seems doubtful one could buy it separately though. I've seen other posts about replacing the bushings with needle bearings. Seems like that would make a bigger difference.

  4. #4
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    The newer style Fox hardware can be ordered direct from Fox or LBS, here is a link to more info:

    New type of Fox shock mounting hardware - Mtbr Forums

    The other option, the needle bearings can be purchased from RWC, their website link is below.

    ABOUT RWC SHOCK EYE NEEDLE BEARING KITS

    As there is not much suspension bearing rotation with the PM4 (compared to say a Santa Cruz Blur XC), the benefits will likely be limited with either choice. Small bump compliance should improve. It would be interesting to have someone test both and report back.
    "If I should die darling in your arms, what a lovely way to go..." Don Felder -All of You

  5. #5
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    I have the RWC bearings on my Mach 4 and my 5.7, and I appreciate the upgrade. The DU bushing was a good fix for pedal bob before the engineering and design caught up, now it's just extra resistance. The bearings take the initial step out of the transition when the suspension cycles, even though there is not very much movement at the eye. I think it is a smoother ride.

    The RP23 is a good shock, and the damper parameters are tuned for our frame. I can't see any reason to spend the money for the CTD feature, when the Mach 4 offers such an excellent pedaling platform to begin with. If it ain't broke, don't spend money on it. If you want to spend $600 for a gain in performance, buy a good wheelset.
    Go out and ride your bike


  6. #6
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    Thanks for the info, guys. It definitely ain't broke. Although, I've only ever done the oil and seal replacement maintenance on the shock. Maybe it's time I had the internals overhauled after three years as my half-time bike.

  7. #7
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    ^ that's a good call. Had my M4 shock done by Toxoholics a few weeks ago, glad I did. It's a shame you can't service your own damper with Fox, but at least getting rebuild kits for the main body is always going to be easy...
    Go out and ride your bike


  8. #8
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    Thought I would add these links below in case someone wants instructions on replacing the Fox shock mounting hardware. At some point all of us will need to replace the worn bushings. As mentioned in this link, the lower bushings are the first to develop play on the PM4.

    AustinBike.com - 2013 Fox Shock Bushings


    You can also find more information on Fox’s website:

    WebHelp


    Under Table of Contents (left upper side), go to the search field and type in:

    Rear Shock Eyelet Hardware Maintenance

    Then click on the selection (should be ranked number 1 on the list). Click on the photo called 5-piece Flanged Bushing.

    Hope this helps.
    "If I should die darling in your arms, what a lovely way to go..." Don Felder -All of You

  9. #9
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    Good article, Maluco. Thanks for posting the link. Although it ends rather abruptly. I liked seeing close-ups of the worn parts.

    This has been very educational for me. I had 4 Fox bags/rebuild kits. I don't remember where they came from, but they must have come from Pivot with my Mach 4 frame. I know I didn't go out and buy them. 3 were seal kits, and the other one had 6 of the same part and I didn't know what it was. Turns out they are replacement DU bushings. I have used 2 of the seal kits, but none of the replacement DU bushings. Methinks it's time to remove the shock and inspect the bushings for wear. Since I still have 3 complete sets of replacement DU bushings, it's not likely that I'll upgrade to either the new Fox bushings or the RWC needle bearings anytime soon, but at least now I know what's available. Thanks again!

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