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  1. #1
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    Stumpjumper FSR Pro Carbon rear shock PSI

    I have a carbon pro, a fantastic bike. Stiff, confidence inspiring, nimble - love it.

    For my svelt like 200lbs (With clothing, camelbak etc) I should be setting the shock at about 200-215 PSI. I have found myself bottoming out the real shock on small 8" kerb jumps. So have upped the PSI to 250.

    Anyone know if its normal to set the rear shock higher than the manufacter recommendations.

    Also only used FOX rear shocks previously, which need there air topped up very infrequently. My Specialized AFR shock lost 40 PSI on a 3 hour XC ride, lots of mud but nothing to challenge the shock. Is this standard or is there something dodgy with my rear shock.

    Thanks for any help.

  2. #2
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    I run 210 for my svelte like 190lb nekked... So it sounds like 215 should be about right, but then I have the Fox brain and not the AFR...
    Building: ​Boardman 2010 HT Pro
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  3. #3
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    Reae shock psi

    Itoo have the new spec rear shock. On my SW Stumpy i am running 15%higher than reccomended psi . It seems to work well. In my past bikes , the factory settings were low also.

  4. #4
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    Shock pressure

    I've ensured I use all of the travel on most trails using 85% of my body lbs.

  5. #5
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    The shock still should not be losing air like that. You may have a seal problem.

  6. #6
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    Sag

    You should always set the AFR shocks to SAG, and not go by what the book says. Really on any shock you should set it to the correct SAG settings to get the best performance. The manual will tell you what the proper SAG setting should be.

  7. #7
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    How long have you had this killer bike? I am debating this bike or a Blur LT any recommendations on what you guys like better. I am a little worried about the durability of the carbon

  8. #8
    I CAN ALWAYS GO BIGGER
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    Read the manual that comes with the bike and ajust accordingly

  9. #9
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    I noticed that when I take the pump off, it loses 15 psi from the valve being half open while unscrewing the pump. I pumped my shock up to 190, then took it off and put it back on, and it read 165. So I always pump 15 over recc. Maybe it's my crappy pump, but I reccomend you guys try it...

  10. #10
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    Yeah , my local shop came to that same conclusion... So I always up the pressure to take into account that there will be pressure loss.. Between 10-15psi depending on the pump that I used.
    Building: ​Boardman 2010 HT Pro
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  11. #11
    MTC rep for LPCPCAC
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    Be careful with the assumption that the air loss is from the disconnect of the pump. Most often the (assuming a properly working valve) the air loss is not from the disconnect. Rememer that the air chamber is extremely small and each time you re-attach the pump, air is passed to it so the pressure gauge registers. If you are adding 15 lbs over the recommended pressure and assuming it will be bled off on the disconnect, your shock will be over pressurized until the next time you attach the pump.

    For most of us this will not cause a big problem other than a stiffer ride than you hoped for. If you are pushing the shock pressure limits due to weight or ride desire, you could wind up blowing it out.

    Just my 2 cents.

  12. #12
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    But, if air is bled off from the disconnect, then it does give you the pressure you want. I noticed that everytime with my time after re-attachting it, there is 15 less psi then when I origonally took it off. So I need to, and I don't over pressurize my shock

  13. #13
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    Idea!

    Its your shock, treat it as you wish....

    The reason the presure is lower on the second read is the jump will use the air in the shock to pressure itself to match the shock.

    Now think about it. It you take pressure out of something (shock) and add it to another space (pump) what do you think happens to the original pressure?

    Class?

    Right, the total pressure will decrease! In our case it is by about 15 lbs/sq ft. I'll even lay odds that if you disconnect the pump and reattach it, the pressure will again drop.

    Now before you say this is caused by the disconnection, you could leave a pressure gauge attached to the fork as you disconnect the pump. I doubt you would see the pressure drop. When you reattach it, the pressure will drop by the proclaimed 15 lbs.

    So back to my original statement; If you are not careful, you can overpressurize the shock.

    While Physics may not be the most glamerous of fields, it is very important for mountain biking.

  14. #14
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    Shock pressure

    Quote Originally Posted by Stumpy_Steve
    I noticed that when I take the pump off, it loses 15 psi from the valve being half open while unscrewing the pump. I pumped my shock up to 190, then took it off and put it back on, and it read 165. So I always pump 15 over recc. Maybe it's my crappy pump, but I reccomend you guys try it...

    The shock does not loose that much pressure when you disconnect the pump. It's when you reconnect the pump that the pump fills up with air from the shock and you loose some pressure from your shock. I run my shock at about 10% above the reccomended air pressure.

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