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  1. #1
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    Anyone know what to do with the piggy back air pressure on the ISX-4 Evolver?

    I was working on my bike and just discovered a valve that I hadn't noticed before at the end of the piggy back. I checked the air pressure and it looks like it has 150 psi in it.

    What is the purpose of this?

    What will more or less air pressure do?

    Is the max pressure like the SPV where it is 175 PSI or like the main cylinder where it is 300 psi?

    There isn't too much good info in the manual since it covers the entire line of Manitou shocks in a couple pages.

    Also when they say that something is more or less "progressive" what are they referring to? It has settings to make it more or more or less progressive. I'm assuming that more progressive means that the shock will get stiffer the further into the stroke it goes. Is that correct?

  2. #2
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    Found my answer, looks like it controls the compression damping.

  3. #3
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    I think that is for the bottom out assist and the pedaling platform... More air and you'll have firmer pedaling and better bottom out assist. I usually run mine as low as possible as my priority is to get a working suspension and not pedaling effieciency but to each his own... There are also knobs there to change air volume for the shock which will effect how progressive the bottom out is...

    Depends on air max pressure. I think max is for the main chamber which is 300... not too sure about the piggyback... check the manitou website hbsuspension.com.

    Progressive means it get's firmer towards end stroke of travel... Once again it depends on what kind of a ride you want and what kind of a rider you are. All about personal preference...

  4. #4
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    Then if I'm concerned with pedal bob, I should increase this pressure. It seems to be eating up the bumps pretty well so I don't think it needs to be decreased. Is this an SPV shock? If so is this the SPV pressure?

  5. #5
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    Quote Originally Posted by big_mountain_biker
    Then if I'm concerned with pedal bob, I should increase this pressure. It seems to be eating up the bumps pretty well so I don't think it needs to be decreased. Is this an SPV shock? If so is this the SPV pressure?
    dont think bob is that big of a concern on the Atlas with the high main pivot... the pedal feedback from the chain should be enough to keep it bobbing... And yea, the ISX4 is an SPV shock. The air you put in there pushes the SPV valve against the orifice in the damper... the higher the pressure, the harder for the orifice to open and so the less sensitivity but better pedaling... It's always a give and take situation... XD Just mess around with it and figure out what you like best and whats best for the terrain you ride... takes time to get suspension setup. It's a fun process... XD

  6. #6
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    Im 180-185 & just recently dropped the pressure to 135 & it seems to be pretty sweet. Im going to drop it to 125 then work on the compression & bottom out from there. What is you weight & riding terrain??
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  7. #7
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    I weigh 320 pounds, I'm currently running 240 psi in the main can and 140 in the piggy back. I typically ride on relatively flat single track with lots of small rocks so I like to set up my suspension to deal with small high frequency bumps, I also ride some fire roads with lots of climbing and high speed descending with small bumps. If I understand correctly I want very little compression and rebound damping and don't want it to be progressive.

  8. #8
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    Quote Originally Posted by big_mountain_biker
    I weigh 320 pounds, I'm currently running 240 psi in the main can and 140 in the piggy back. I typically ride on relatively flat single track with lots of small rocks so I like to set up my suspension to deal with small high frequency bumps, I also ride some fire roads with lots of climbing and high speed descending with small bumps. If I understand correctly I want very little compression and rebound damping and don't want it to be progressive.
    Don take me wrong here but you will have to expiriment with pressures to find what works best because im quite a bit lighter & we are talking a huge differance. mrperc & i ride together allot, he's possibly 120 & im 185. Originally there was about 145 in the piggy back, I would run about 110in the main can & mrperc i believe was running 80. Your probibly fine on the piggy back, set the sag at about 30% for the main can. How does it feel when your riding??
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  9. #9
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    At 240 psi I'm getting around 30% sag and in the least progressive setting I've gone through about 3/4 of the travel max. I would say that it feels pretty good, although I don't have much to compare it to besides my hard tail. I might try decreasing the rebound damper a little today to see if it takes the small bumps a little better.

  10. #10
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    Quote Originally Posted by big_mountain_biker
    At 240 psi I'm getting around 30% sag and in the least progressive setting I've gone through about 3/4 of the travel max. I would say that it feels pretty good, although I don't have much to compare it to besides my hard tail. I might try decreasing the rebound damper a little today to see if it takes the small bumps a little better.
    try running less air in the main chamber seeing as you're not using all of your travel... Right now i think your bike would feel like a XC rig with only 4"... probably less then 4"... If you want small bump sensitivity then your pedalling efficiency will have to be affected... Rebound is a whole different thing too... The idea for rebound (at least for me) is to get it to rebound as fast as possible without bucking me over so that it's always prepared for the next hit and doesnt collect...

  11. #11
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    mrperc & I have been disagreeing on rebound for over a year. He likes the rebound fast like a flea in heat, i like mine set when you push down it comes back almost as fast as you. To little on the rebound & it packs up & not enough it'll buck you over. Each person has a different opinion on this.

    Lets give this a shot 120 & 210 psi with just enough rebound that when you go up it fallows at the same speed. I use my forearm on the seat push body weight down then release.
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  12. #12
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    Quote Originally Posted by dogonfr
    mrperc & I have been disagreeing on rebound for over a year. He likes the rebound fast like a flea in heat, i like mine set when you push down it comes back almost as fast as you. To little on the rebound & it packs up & not enough it'll buck you over. Each person has a different opinion on this.

    Lets give this a shot 120 & 210 psi with just enough rebound that when you go up it fallows at the same speed. I use my forearm on the seat push body weight down then release.
    and you were telling me how slow my sherman rebounded last time... XD Keyphrase... "Fast but not bucking you over"

  13. #13
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    Dropped the pressure and decreased the rebound damper for the ride yesterday. It was more plush and responsive for sure although it did feel a little more squishy when pedaling as expected. I was using up most of the travel, but didn't do any drops, I am pretty sure I would bottom out on a 1 footer. Is it okay to bottom out? I'm wondering if I should keep the same lower air pressures and choose a more progressive setting, might try that on the next ride.

    At this point I think the rear shock is getting pretty close to proper tuning, the fork is definitely not though. I dropped the pressure on both the main can and SPV a bit. It takes the big bumps no problem, but on a high speed descent it seems to react too slowly to the small stuff, what should I change? I'm assuming I should decrease the rebound damping, should I also drop the SPV pressure?

  14. #14
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    Quote Originally Posted by big_mountain_biker
    Dropped the pressure and decreased the rebound damper for the ride yesterday. It was more plush and responsive for sure although it did feel a little more squishy when pedaling as expected. I was using up most of the travel, but didn't do any drops, I am pretty sure I would bottom out on a 1 footer. Is it okay to bottom out? I'm wondering if I should keep the same lower air pressures and choose a more progressive setting, might try that on the next ride.

    At this point I think the rear shock is getting pretty close to proper tuning, the fork is definitely not though. I dropped the pressure on both the main can and SPV a bit. It takes the big bumps no problem, but on a high speed descent it seems to react too slowly to the small stuff, what should I change? I'm assuming I should decrease the rebound damping, should I also drop the SPV pressure?
    Up the bottom out ressistance on the piggy back... there's a dial there to change the air volume... I'd suggest decreasing the air volume. When you decrease the air volume, the air pressure adds up too... So you might want to play with that a little... It's ok to bottom out occasionally though it's best to almost bottom out all the time and not actually hear the clunk of the bottom out...

    What fork are you running??? If it's an SPV fork, i'd suggest devolving it... Night and day difference... trust me... rode dogonfr's Manitou Minute with the SPV then rode it devolved and it was awesome... also riding my Sherman Slider devolved too... Basicly it takes out the SPV valve in the fork changing it almost to a TPC feel... So you might sacrifice a little pedaling but your bump sensitivity increase insanely...

  15. #15
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    Yep I'm running the 140mm Manitou Minute SPV, this "devolving" procedure seems interesting. I'll look for some info on how to do it.

  16. #16
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    Devolve it... heres a thread about it... XD

    SPV Devolve

  17. #17
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    An idea of what our devolved forks go through... XD

    http://alloutprodux.com/condro.mov

  18. #18
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    That's some super sweet down hillin'

    Nice video.

  19. #19
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    Quote Originally Posted by big_mountain_biker
    That's some super sweet down hillin'

    Nice video.
    you should come join us in the east bay dude... you're only in san jose... XD Meet up halfway in oakland... XD

  20. #20
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    Quote Originally Posted by mrpercussive
    you should come join us in the east bay dude... you're only in san jose... XD Meet up halfway in oakland... XD
    Heck ya he should, Atlas can handle all that stuff.
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  21. #21
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    Thanks for the offer guys, no place else on MTBR can you find people as helpful and close as the Ibex board.

    I'm sure the Atlas can handle it, just not sure I can yet. Used to do a lot of down hilling when I was in High School, but its been 10 years since then and I weigh about twice as much as I did then. Once I'm down to the mid 200's I'll definitely join you guys.

    I've lost about 80 pounds since I decided that sitting around all day and eating pizza wasn't a good idea. With all the riding I've been doing on the Atlas I'm sure it won't take long too get to that point.

    Can't wait to start doing stuff like that again.

  22. #22
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    we're all a bunch of out of shape dudes anyways... and we wait for people... XD

    plus oakland isnt that hard... XC guys do it... But whenever you feel like it though, let us know. We'll show you around... XD

  23. #23
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    You can definitely expect a PM from me in the not too distant future asking to join up with you guys on your next ride.

  24. #24
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    Quote Originally Posted by big_mountain_biker
    You can definitely expect a PM from me in the not too distant future asking to join up with you guys on your next ride.
    Yup like the perc one said just come on out & ride. There is no pace you must fallow, you ride your ride & we allways wait allong the way. We wont send you in over your head & if you need to work on something we will help. Im not one to invite someone on a ride then leave them in the dust. Your welcome Any time dont worry about a thing just come out & have fun.
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  25. #25
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    Quote Originally Posted by dogonfr
    Yup like the perc one said just come on out & ride. There is no pace you must fallow, you ride your ride & we allways wait allong the way. We wont send you in over your head & if you need to work on something we will help. Im not one to invite someone on a ride then leave them in the dust. Your welcome Any time dont worry about a thing just come out & have fun.
    all about having fun... XD

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