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  1. #1
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    Monarch RT3 on a Motobecane Fantom Pro DS setting question

    Hello everyone. So I've been having some problems with my rear shock. It's a 2012 Rock Shox Monarch RT3. Despite all of the good reviews, I could never get the shock set to proper sag for my weight.

    The shock is a 2012 (I think) Rock Shox RT3
    165x38
    Says ML (M in blue box and L in red box)

    My bike frame is a 2010 Motobecane Fantom Pro DS
    I weigh 190lbs

    I've been searching around the forums and found some articles all about the monarch and leverage ratios etc. Someone once told me that the Fantom DS frame has a leverage ratio of 3.33:1 in the 5in travel setting. What are the leverage ratios for the 4in and 3in settings? How can I calculate this? How do I interpret the chart in this article in the first place? I also don't know the equivalent ABCD tune for my shock as it only says ML

    2011 Monarch RT3 for my Enduro

    Somewhere I read that leverage ratio is calculated by taking the travel over shock travel. If that's the case. then I presume that I need to convert the inches to mm. However, if I take 5in and convert to mm I get 127, then 127/165 does not equal 3.33. So I'm doing something wrong there.

    Anyways, so that's me trying to think about things outloud. My problem is that I have to top the shock out at 250-260psi (I always tend to lose psi when I disconnect the shock pump) to even get 30-35% sag in both the 5in and 4in travel settings. That doesn't seem right as the shock is rated to only go to 275psi. I would guess that I have a low tune shock and need a medium tune shock. I just wanted to know all about the leverage ratios and what not so I could prove it to myself.

    Is there any way to tune the shock using the IFP pressure to suit my weight? I found a nice article all about that, but I really don't know much about the whole theory behind IFP. Monarch & IFP pressure change...

    Do I need a new shock? In the 3in travel setting I can get 25% sag with about 190psi. I want to run in the 5in travel since I tend to like jumping off stuff. If my frame can allow more travel why not right? If not 5in travel at least 4in.

    Thanks.

    The attached photo is of the shock in the 3in travel setting. the shock is current flipped upside down and in the 5in travel setting.
    Attached Thumbnails Attached Thumbnails Monarch RT3 on a Motobecane Fantom Pro DS setting question-img_1646.jpg  


  2. #2
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    Leverage ratio calculation : 5" / 1.5 = 3.333, 4" / 1.5 = 2.666, 3" / 1.5 = 2.0.

  3. #3
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    To add to the above post, you can see that he took the stroke of the shock not the total eye to eye length of the shock for the calculation.

  4. #4
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    Thanks for the calculations. Now I just have to figure out how to read that chart in the other thread. Also, would changing the IFP pressure help to change the "tune" of the shock? It seems like I'll need a medium tune rather than the light tune that I think I have now. Could anyone confirm this? Thanks.

  5. #5
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    Quote Originally Posted by Koin View Post
    Thanks for the calculations. Now I just have to figure out how to read that chart in the other thread. Also, would changing the IFP pressure help to change the "tune" of the shock? It seems like I'll need a medium tune rather than the light tune that I think I have now. Could anyone confirm this? Thanks.
    In the 5" mode you are going to need as much compression as you can get.

  6. #6
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    Thanks. That's just the problem though. It seems like I'd need more pressure than the max psi value of the shock to get to proper sag. Also, how can I determine if my bike has a falling rate, rising rate, or flat rate? I'm trying to decipher the chart from the other post.

    Also, would changing the IFP help with this problem? Thanks

  7. #7
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    Quote Originally Posted by Koin View Post
    Thanks. That's just the problem though. It seems like I'd need more pressure than the max psi value of the shock to get to proper sag. Also, how can I determine if my bike has a falling rate, rising rate, or flat rate? I'm trying to decipher the chart from the other post.

    Also, would changing the IFP help with this problem? Thanks
    IFP info : Monarch & IFP pressure change...

    I have had better luck w/ Fox shox's on higher leverage or falling rate frames.

  8. #8
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    Thanks for the info on the IFP. I am waiting for the adapter to come in the mail. I learned how to read the chart and did some research on IFP. I think I can do it and will have to wait to find out.

    Keen, do you know if my frame has a falling rate? That would really help if I knew for sure. I'm also looking at changing the piston on the inside of the shock. Maybe... If I'm feeling lucky that I won't ruin anything. I did some more research and it seems like there is not only a difference in IFP between tunes, but also in the physical piston itself. I watched a video on servicing and I would certainly ask the lbs mechanic for some help. Please correct me if I'm mistaken.

    Also, what exactly do the letters mean ML mean? I think the L stands for low tune, but what about the M?

    Thanks

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  10. #10
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    Thanks keen, I read that article yesterday, but still have the same questions

  11. #11
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    "M" medium tune.
    Rates :
    A bicycle with a rising rate leverage curve produces a bike that is progressively harder to push through the shock stroke, making it hard to bottom out. If we go back to our rock and lever example, a rising rate would be similar to having the metal rod get shorter and shorter the further we pushed the rock. A falling rate (not a very common design currently) would be the opposite - the metal rod would get longer and longer, making it easier to push through the further you go.

    To analyze the rate I'd imagine you would need some fancy CAD program.

  12. #12
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    Right, i got that part; but how do I know what my bike has?

  13. #13
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    how have you liked the bike besides this issue?

  14. #14
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    Quote Originally Posted by Koin View Post
    Right, i got that part; but how do I know what my bike has?
    As I mentioned "To analyze the rate I'd imagine you would need some fancy CAD program"

    Here's a link to a program. There might be more specific programs available.

    Linkage Bike Simulation Software - Details

  15. #15
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    I like the bike very much. Other than the fear of busting the shock because it's not a proper tune for the leverage ratio the bike performs great. Since I don't want to risk breaking anything, I haven't been pushing the bike too hard. Also the floodgate settings do next to nothing.

    Keen, thanks for the link to the software.

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