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Rear suspension leverage and shock stroke size Q

Discussion in 'Downhill & Freeride' started by ChrisRobin, Nov 28, 2005.

  1. ChrisRobin

    ChrisRobin Turbo Monkey

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    Just curious about something:

    Say you have a bike that gets 9" travel with a 2.75 stroke shock but you have the option of using 3.0 to get the same travel. Because of the 1/4" longer, would running the bigger size be better in terms of damping performance (or lighter leverage...etc) or is the difference so small it wouldn't matter?
     

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  2. ncrider

    ncrider Turbo Monkey

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    Is the 3" stroke the same length eye to eye as the 2.75" stroke shock?
     
  3. Secret Squirrel

    Secret Squirrel There is no Justice!

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    When dealing with 1/4" on that small of a scale, it will make a difference. How big of an impact is mostly subjective...some people notice one click on their compression adjuster...It will be better in just about everyway (i.e. damping, friction induced heat, small bump performance, etc....)

    This is all based on the fact that you use a shock of the same or higher quality and it is set-up correctly for the bike and useage....I'm also assuming that there is a different shock position for the two different sizes...but I take it that that was implied...
     
  4. ChrisRobin

    ChrisRobin Turbo Monkey

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    To keep things simple, both shocks will be set up the same but will be different sizes without affecting the frame's geometry. So in the end, all we're comparing are 2.75" vs. 3.0" and the same amount of travel.
     
  5. WheelieMan

    WheelieMan Monkey

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    I'm curious, what kind of bike is it?

    If you have the option, there is really no reason not to use the longer stroke shock, assuming that the different mounting position doesn't radically change the shock rate. The weight difference between a 2.75 and 3.0 shock is what, 1/4 pound?

    I've thought about machining a new plate for my bike that would allow a 3.0 shock to fit (instead of 2.75) but I haven't determined if it would be worth the cost.
     
  6. ncrider

    ncrider Turbo Monkey

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    :stupid: the foes 2:1 is a great example of a longer stroke being a good thing.
     
  7. Cave Dweller

    Cave Dweller Monkey

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    If you use a longer stroke shock but same eye to eye you are going to end up with more travel, unless you somehow modify a linkage to reduce the leverage ratio.

    You need to be careful that the swingarm, wheel and frame will all not contact each other seeing it is going to go 1/4" past where it was designed to.
     
  8. Jm_

    Jm_ Turbo Monkey

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    It depends on how that particular shock is valved.

    All things being equal (considering two stock shocks with the stock valving), the longer stroke shock will feel better, while the shorter stroke one will most likely blow through the travel faster and feel somewhat "undamped" comparably. This is because a 2.75" stroke shock was designed for ~8" travel, not 9".

    On the other hand, some companies (like avalanche) make shocks that have bigger shafts and better seals to deal with the increased forces that are seen on over-leveraged bikes. These shocks are also valved accordingly of course.
     
  9. ChrisRobin

    ChrisRobin Turbo Monkey

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    It's for a Nucleon ST. Technically, the front shock mount can be moved slightly to fit a longer shock. It shouldn't change the shock rate since the longer shock will be in the same position as the stock 8.75" but just very slightly higher in the frame.

    Hmmm...that much weight increase eh?

    I'm all over it. The frame has a ba-zillion adjustment settings. I can put a longer shock in there and keep the same geometry and travel.
     
  10. ChrisRobin

    ChrisRobin Turbo Monkey

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    I didn't think 1/4" stroke would make such a difference. I would like to try a 8.75x2.75 Push'd Fox RC. The stock shock on there was a 9x2.75 Romic. The bike felt great. I don't know if the extra 1/4" stroke is worth all the extra weight.
     
  11. Cave Dweller

    Cave Dweller Monkey

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    Cool.

    Reason i said that is i am getting my avy shortened (from 9.5X3 to 9.375x3 to drop my BB 0.35 of an inch and salcken my head angle on my turner DHR) and i had to be careful about making sure nothing hit.
     
  12. Jm_

    Jm_ Turbo Monkey

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    It would still work, and if everything else is equal, someone may not be able to tell the difference, but if you have two or three factors that are adding up, like over-leveraged shock, incorrect spring rate, too much preload, etc; Then the suspension will feel really crappy, and while it wouldn't be the only factor why, the over-leveraged shock may be contributing.

    What I am talking about is the valving of course, which with fox shocks is not optimal for more than 3:1 leverage ratios. With an avalanche shock this is not an issue because it is valved for the particular bike.
     
  13. maxyedor

    maxyedor <b>TOOL PRO</b>

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    1/4 pound? Are you insane? it will be more lik 1.5-2 ounces:mumble:

    3" stroke all the way
     
  14. WheelieMan

    WheelieMan Monkey

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    I honestly have no idea, just a guess.

    You're right, in that case there would not be a significant rate change. Gotta love the mega adjustability of Nicolais!
     
  15. keeping_it_real

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    Im kinda doing something similiar with a 2004 Norco Aline, Im changing the stock 2.5" Fox RC for a 2.75" stroke DHX. Im keeping the total wheel travel the same by changing the mounting point of the shock onto the shock linkage (also making stronger-less flexy linkage plates). This gives a better shock leverage ratio.
     
  16. banj

    banj Monkey

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    I may be wrong here but I thought the nucleon st only had adjusments on the "front" shock mount...and not on the linkage. Without being able to change the mounting position on the linkage you can't reduce your shock rate so with a 3" stroke shock you'll be getting around 9.8".

    As I said though I could be wrong and as long as you can adjust your position on the linkage as well as the main frame shock mount then you'll be able to get something that works.
     
  17. ChrisRobin

    ChrisRobin Turbo Monkey

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    It's the front shock mount you're not supposed to really mess with. The rear has all the adjustments. On the main linkage (at the rear shock mount), you have three travel adjustments. From there, the bits connecting the linkage to the swingarm has three more adjustments. And I still have bottom bracket height adjustment. My idea is to get the longest stroke shock in there with the highest amount of travel with the lowest bottom bracket height.
     
  18. ChrisRobin

    ChrisRobin Turbo Monkey

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    Even with a Fox RC that's been sent to Push to upgrade the internals?? Otherwise I'd be sticking with a 9.5" Romic.
     
  19. BMXman

    BMXman I wish I was Canadian

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    hey CR if I remember right some of the team tried to run a 3" stroke and ran into fitting and clearance ploblems. I will fit but when you cycle the suspension there will be contact in some areas...you can still make it work but you will have to do some filing...D
     
  20. Secret Squirrel

    Secret Squirrel There is no Justice!

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    I ride a Push'd RC and it's great. Get the Race package (even if you don't race...) ...you get to toss in your weight, riding style, and leverage ratio (along with some other info..)...so the guys dial it in just right!! Really good internals (almost all of them get switched out for better stuff!) and if you can find one, go with a Ti spring. It'll be worth it!
     
  21. ChrisRobin

    ChrisRobin Turbo Monkey

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    Hey, hope the leg is doing better!

    As for the shock, I'd be moving the front shock mount a hole or two up the downtube. At that point, I won't be able to use those black brackets that secure the Rohloff cables but that's ok since I have an external shift box. I can neatly tie-wrap them down. I remember doing this a couple years ago with a bigger Romic shock. I'd only be able to put the bigger shock in the middle hole of the rear shock mount (otherwise the shock linkage hits one of the mounts for the Rohloff hub). I 'think' that will leave me at 9" travel with all the other....AHHH screw it! I'll stick with Romic 9x2.75: the stock team setup. Ideally I'd like a 9.0x3.0 but only Avalance and Risse makes those sizes.

    edit. If I do manage to fit it on there, that means I'd be stretching out the adjustments to their maximums and I'll never be able to change anything about the frame. I should stick with the stock setup.
     
  22. Jimmy_Pop

    Jimmy_Pop Turbo Monkey

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    I wish there were more options for the 9" eye to eye. I was surprised lately with all the weight comparisons between the Avy vs the competition. it made me feel better about running my Ti Avy.

    Ive thought about buying a 9x2.75" Romic just to see the weight and valving difference. All the progressiveness of my suspension is built into the linkage of the frame so the valving of my shock needs to be linear. yeah, it will cost me alittle travel. I can slide the Ti spring off my Avy right on the Romic. I could keep the Romic for shorter, smoother, less gnar courses when i use the single ply ust tires to help get the weight down.

    the best thing i can do to improve my bikes suspension is loose 20 pounds off of myself. I'm all worried about 1/2 pound on my bike when my bike is screaming at me to lose 20 ya fat fvck.
     
  23. ChrisRobin

    ChrisRobin Turbo Monkey

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    I think it was Kanter that said he didn't see much of a difference between his Romic and then Avalanche shock. What made him happy was knowing the Avy shock had the reliability.
     
  24. ChrisRobin

    ChrisRobin Turbo Monkey

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    I didn't want to start up a new post about this but as I was looking around the buy and sell forums, I noticed something that got me wondering: why would Santa Cruz still use 2.75" shocks on v10s???