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  1. #1
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    Anyone install Fox RP23 Shim/Volume Spacer on Mojo?

    Has anyone played with either Fox shims or homemade ones (like DG's from Turner's forum)? I found myself using up a lot of the low/middle part of the travel on my SLR, so I thought about shimming it. Maybe the small sized one and lower the air pressure. BTW 2011/12 Turner Spots come with medium shims already installed. Here's a writeup for those who are unfamiliar:

    Tech Tuesday - How to Install a Fox Float Air-Volume Spacer - Pinkbike.com

    I haven't opened up my RP23, but I assume there are no shims in there currently.

    If Hans or Dave Weagle can chime in, that would be great too!

  2. #2
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    Don't need hans or anyone else to chime in, alot of people have done it. There are multiple threads about the rp-23 blowing through it's travel too easily. put the medium spacer in mine. (mojo HD) an now running right about my body weight for pressure and not bottoming out and right at 30% sag....
    determined to put the "mountain" back in "MOUNTAIN BIKING!!!" "HIT IT!"
    2012 MOJO HDeeeeeeee!!!!
    2010 scott CR1 comp

  3. #3
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    I'm having problems trying to get the air spacer kit in Australia and I don't want to spend $40 on postage to get it. Could someone who has one give me the basic dimensions, ID,OD and the wall height and thickness of the larger spacer. Then I can cnc some out of hdpe.

  4. #4
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    You can use CD packaging, among other materials. Check out DG's write up in the Turner forum. Search using "shim" or RP23, etc.

  5. #5
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    Quote Originally Posted by Cable0guy View Post
    You can use CD packaging, among other materials. Check out DG's write up in the Turner forum. Search using "shim" or RP23, etc.
    I used the plastic from a CD/DVD container. Works well. Make a set of shims and pick the one that works best.

  6. #6
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    I have read the turner forum. The spacers they make seem to have a lot less volume than the .6 cubic inch fox spacer. I should probably just open the shock up and make my own measurements.

  7. #7
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    The shaft in the rp23 is 10mm so the ID of the spacer should match that.... but you're right, you should measure it. I put the med Fox spacer in mine and it was a big improvement... never had a reason to measure the diameter of them though. If nobody else answers you I can measure one next week when I'm back home.

    EDIT: I'm just remembering that the volume reducer spacers from Fox are designed to fill the void in the top of the shock body without changing total travel, and as such they don't snap onto the shock shaft at all (that was the 10mm diameter I was referring to). Anything that goes onto the shaft itself will mechanically limit the travel by causing the shock to bottom sooner against the spacer. The Fox spacers are contoured to snap onto the base of the shaft up in the top of the shock body...so it's larger diameter then 10mm, and from memory I'm thinking it may have a beveled shoulder or slight taper to it.

    Personally, I think the clean execution, reasonable price (relative to a lot of bike stuff), choice of 3 included sizes, and noticeable benefit all argue in favor of just buying the fox kit... and I'm generally a DIY kinda guy. Of course, if I had access to a CNC mill I'd probably feel differently about a lot of things
    Last edited by doismellbacon; 02-09-2012 at 12:04 PM.

  8. #8
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    Thanks doismellbacon,

    I was just worried about the OD mainly as it seems to be quite a bit smaller than ID of the
    air can, so I thought it must have to clear something and I just wanted to play it safe.

  9. #9
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    The easiest and cheapest way to do it is to slide the outer chamber off and install a home made shim in there. Some will say they don't trust it, blah blah blah. There isn't anything to not trust, you're just reducing the volume of the can(most importantly when its under full compression). Period. And no, there's no way this mod would increase the heat of the shock any noticeable amount; Its not compressing the gasses enough to cause that, and its not interfering with any moving parts.

    Link to instructions here: DW 5 Spot RP23 mod

  10. #10
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    See my edit above.

  11. #11
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    Quote Originally Posted by Tim-H View Post
    The easiest and cheapest way to do it is to slide the outer chamber off and install a home made shim in there. Some will say they don't trust it, blah blah blah. There isn't anything to not trust, you're just reducing the volume of the can(most importantly when its under full compression). Period. And no, there's no way this mod would increase the heat of the shock any noticeable amount; Its not compressing the gasses enough to cause that, and its not interfering with any moving parts.

    Link to instructions here: DW 5 Spot RP23 mod
    Umm what if you dont have a HV shock, ie like all the mojo/sls

  12. #12
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    The trouble here is I can't even find the price of the kit from the local distributor. If I had the measurements I could draw it cut and have the job done quicker than the time it would take to go to the lbs and the time he would have to spend on hold to the local distributor while they found the right person to talk to and then they would probably have to have it sent from the USA and I would end up paying anywhere between 2 and 4 times what it costs in the States and waiting god knows how long. I have been waiting for more than 3 months for springs for eggbeaters from a different distributor. I contacted Crank Brothers but they told my to go through local channels. So now I'm trialing both look and time pedals.

  13. #13
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    Where are you, Tatooine?


    I'll post some dims and pics from one next week. Sm or LG will be easiest because they're not installed, and ID and OD won't vary.

    A post above made me wonder.... Can you use the "inner wall of the can DIY shim technique" on a shock with the standard volume air can? There's not enough room in there, is there?

  14. #14
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    I live in Canberra.
    We had the Worlds here a while ago. Great place to ride but it is a pretty small city only about 350K people.

    The dimensions on the large will be all that I need, thanks. As I probably shouldn't make anything larger than that to be safe.

    I don't think there is enough room to reduce the volume via the DIY technique.

  15. #15
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    I;ve installed the medium Fox reducer onto my Mojo SL's RP23, but unfortunately I've not tested it out yet as I've had a chest infection for the past 3-4 weeks. Hoping to get out this week and tinker with air pressures. Hoping to be able to drop the air pressure to get more initial small bump sensitivity and then not bottom the shock out on 2-3 foot drops

  16. #16
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    Quote Originally Posted by dreednya View Post
    I;ve installed the medium Fox reducer onto my Mojo SL's RP23, but unfortunately I've not tested it out yet as I've had a chest infection for the past 3-4 weeks. Hoping to get out this week and tinker with air pressures. Hoping to be able to drop the air pressure to get more initial small bump sensitivity and then not bottom the shock out on 2-3 foot drops
    I think you'll get what you're looking for. I went from 165 psi w/ 20% sag and midstroke wallow, to 145 psi w/ 30% sag and a much nicer progression through the stroke.

  17. #17
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    Sounds good doismellbacon. Looking forward to first ride with the setup tonight . Going to take my shock pump in case I need to tinker

  18. #18
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    Here is the Official Fox Shock How To.

    Changing FLOAT Air Spring Compression

  19. #19
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    Sorry for the slow follow-up....super busy week.
    The Fox large volume reducer is:

    14mm ID
    38mm OD
    the slot that allows for installation is 9mm, maybe a bit more
    17.5mm height
    5mm wall thickness
    6.5mm base thickness
    2mm thick lip that's about 2mm tall

    The smallest spacer is a simple disk shape, with a hole and a slot:
    14mm ID
    38mm OD
    9-10mm slot
    6mm thick

    The medium spacer is currently in use, but you can use your imagination.. it's a shorter version of the large one.
    Attached Thumbnails Attached Thumbnails Anyone install Fox RP23 Shim/Volume Spacer on Mojo?-fox-rp23-lg-volume-shim-dims.jpg  


  20. #20
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    Given this thread, and Yody's report on a similar mod, and feeling like I'm also going through my travel on smaller hits than I'd expect, I'd like to give this a try too.

    1) Anyone know where to order this part? Google doesn't deliver for the part number and I don't see it on the fox online store.

    2) Given that so many have commented on this as a great mod for the HD, I'm curious why Ibis doesn't spec it as standard equipment? The HD was designed before these higher-volume RP-23's hit the market, right?

    3) Are there any benefits to using the larger volume shock unmodified? Does it work better for some rider sizes or riding styles?

    Thanks.

  21. #21
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    Quote Originally Posted by mikemikemike View Post
    Given this thread, and Yody's report on a similar mod, and feeling like I'm also going through my travel on smaller hits than I'd expect, I'd like to give this a try too.

    1) Anyone know where to order this part? Google doesn't deliver for the part number and I don't see it on the fox online store.

    2) Given that so many have commented on this as a great mod for the HD, I'm curious why Ibis doesn't spec it as standard equipment? The HD was designed before these higher-volume RP-23's hit the market, right?

    3) Are there any benefits to using the larger volume shock unmodified? Does it work better for some rider sizes or riding styles?

    Thanks.
    all very good questions I too would like to know as I haven't been able to order the part either to try it out...

  22. #22
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    I ordered mine from my LBS. They were not yet aware of it but were able to contact Fox or QBP or somebody and get it quickly.... the interweb is no substitute for a local bike shop with good ole fashion service. (props to The Bicycle Sport Shop in Austin)

    I'm sure that Ibis, and other mfr's, tune their suspension for the ride characteristics that they like and that they think will appeal to the broadest number of riders. But the ideal tune for you is dependent upon your weight, riding style, bike setup, preferences for feel, and the trail you're riding. Most DH pros will change their setup for individual tracks even though all those other variables are constant. That's why custom tuning can be so beneficial for many people, then it's dialed for you, rather than a compromise for the average middle of the bell curve theoretical rider....and why it's really cool that Fox offers these options and other DIY alternatives have been shared.
    All else equal, a larger volume shock will give you a flatter (less progressive) spring curve, so for instance, a really light weight rider who wants a plush ride w/ full travel, and who isn't hitting a lot of jumps and drops, may find a higher volume setup better. Likewise, a heavy aggressive jumper will need more midstroke and bottom out support which can be achieved by lowering the volume and creating a more progressive spring curve.... and of course there are infinite shades of grey in between.

    I think the Mojo / Mojo SL really benefits from lower volume and a more progressive spring....but of course that's filtered through all my preferences, weight, etc etc. Apparently the spring curve on the HD is quite a bit different from the SL, so it will excel with a different shock setup. At least, that's what I'm reading from HD owners here, and being told by the guys at Push...but I can't comment from my own experience....not yet anyway...

  23. #23
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    You can order it from fox by phone
    _______________
    1x10 IS SO FINE on my 21.9 lbs IBIS SL-R
    11-36 XTR in the rear, 36T wide-narrow upfront

  24. #24
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    homemade spacer

    Thanks again for the diagram. I made a spacer out of some 12mm thick HDPE chopping board.
    Attached Thumbnails Attached Thumbnails Anyone install Fox RP23 Shim/Volume Spacer on Mojo?-air-spacer-small.jpg  


  25. #25
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    Well I installed the large spacer and I'm much happier with the RP23. I weigh 235lbs with gear and now I can run much lower pressures and the rear feels better.

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