using a 2.25" stroke shock on a frame intended for a 2"stroke?- Mtbr.com
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  1. #1
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    using a 2.25" stroke shock on a frame intended for a 2"stroke?

    I am looking at putting a 7.78 X 2.25" shock on my frame intended for a shock 7.78 X 2". Am i going to run into trouble here? Is this possible without killing my frame?
    ANYONE?

  2. #2
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    the shock with longer stroke must compress to a shorter length i2i, so it would be very important to cycle the suspension to see it if binds (tire/frame/link etc).

  3. #3
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    Quote Originally Posted by fsrxc
    the shock with longer stroke must compress to a shorter length i2i, so it would be very important to cycle the suspension to see it if binds (tire/frame/link etc).
    And as long as it doesn't bind, it should be a good move. It will lower your leverage ratio.

  4. #4
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    It does not lower your leverage ratio. Same ratio is used to acheive more travel.
    Whether or not it will work depends on the frame, you'll have to check carefully for clearance. Front derailleur smacking the chainstay, the tire contacting the seattube, rocker arm contact, etc. Also depends on the size of the frame. My medium Kona Coiler uses a stock 7.875x2.0 shock. The guy I bought the frame from threw a 7.875x2.25 shock on. No clearance issues. Some people with smaller frames claim that the QR seatpost clamp will smack the rocker arms.

  5. #5
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    How would it change the leverage ratio?
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  6. #6
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    ok, I may be wrong about the leverage ratio. I'd been told a longer stroke would equal a lower leverage ratio. I did not realize it may change the amount of travel.

  7. #7
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    I had the stroke increased to 2.25 from 2.00 on my Fifth Element with no problems whatsoever. The almost 3/4" additional travel is very noticeable.

  8. #8
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    Quote Originally Posted by Jwiffle
    ok, I may be wrong about the leverage ratio. I'd been told a longer stroke would equal a lower leverage ratio. I did not realize it may change the amount of travel.
    The leverage ratio is a function of the frame design; the amount of stroke and your leverage ratio together determine the amount of travel...now, if you changed the eye to eye length, that would probably be changing the frame's leverage ratio...
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  9. #9
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    No, I'm pretty sure changing the i2i length doesn't change the ratio. Changing the rocker plates does though.

  10. #10
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    Where are the engineers when ya want one?
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  11. #11
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    Quote Originally Posted by Bikinfoolferlife
    The leverage ratio is a function of the frame design; the amount of stroke and your leverage ratio together determine the amount of travel...now, if you changed the eye to eye length, that would probably be changing the frame's leverage ratio...
    If the wheel travel stayed the same when a longer stroke shock was used then the leverage ration has changed. To do that the rocker would have to have been changed. If you keep the same rockers and toss on a longer stroke shock, you only change the wheel travel, not the leverage ratio.

    An example, the newer Truth's have a 2" stroke shock, old ones had 1.5" stroke, wheel travel is the same, the rockers were changed and the leverage ratios are different.

    i2i doesn't make any difference, only the stroke and rocker design.

    Monte
    (not an engineer, just does some math here and there)

  12. #12
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    Quote Originally Posted by Bikinfoolferlife
    The leverage ratio is a function of the frame design; the amount of stroke and your leverage ratio together determine the amount of travel...now, if you changed the eye to eye length, that would probably be changing the frame's leverage ratio...
    The shock really has nothing to do with the compression ratio, it's the frame design. If you are going to a longer stroke (in this case 2" to 2.25") with the same eye to eye (7.875"), then you are adding the travel to the bottom end. For the first 2" of the stroke the compression ratio is identical to what is was before, and keep in mind that it changes throughout the stroke. What the compression ratio is beyond that 2" depends on the frame design. On the Heckler, (falling rate design) the compression ratio gets higher as you go through the stroke, and the added .25" has a higher compression ratio than the rest of the stroke. On a bike with a rising rate design, it could very well be that the added .25" has a lower compression ratio than the rest of the stroke.

    As far as adding a longer stroke shock, like others said, check to make sure everything clears on your frame.

    As far as the results go, that depends on the design. On a falling rate like the Heckler, that extra travel was very usefull, as the bike goes through those last few inches of travel pretty quickly. When I went from a 2" to a 2.25" stroke shock on my Heckler, I kept my settup pretty much the same, and the extra .7" travel just added to the bottomless feel of the bike.

    However, I could see that on a bike with a rising rate, going beyond the intented travel range could put you into a part of the travel with a rate that is rising too much, and you might not really get full use of the travel without running a bunch more sag (could be a good thing as well) This is just speculation, though.

    Changing the eye to eye length could change the comp ratio because it makes the bike use a different part of the frame's travel, but anywhere the travel of the different shocks overlap the comp ratio will be the same.

  13. #13
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    Thanks, I was thinking sideways. Makes much more sense to think of the leverage ratio of the frame as not being a constant, but rather possibly affected by either a stroke or i-i length change (or link change), it all depends on the designer's intended travel path with particular components involved. I wasn't thinking of changing links in any case as my only experience in changing shock specs was with a Heckler....
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  14. #14
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    "The shock really has nothing to do with the compression ratio, it's the frame design. If you are going to a longer stroke (in this case 2" to 2.25") with the same eye to eye (7.875"), then you are adding the travel to the bottom end. For the first 2" of the stroke the compression ratio is identical to what is was before, and keep in mind that it changes throughout the stroke. What the compression ratio is beyond that 2" depends on the frame design. On the Heckler, (falling rate design) the compression ratio gets higher as you go through the stroke, and the added .25" has a higher compression ratio than the rest of the stroke. On a bike with a rising rate design, it could very well be that the added .25" has a lower compression ratio than the rest of the stroke."

    What size tire are you running on your Heckler. I run a 2.35 Nevegal and want to put a 2.25 stroke on my Heckler-Would it rub on the ST? Thanks

    Brent

  15. #15
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    Quote Originally Posted by ATOMICned
    I am looking at putting a 7.78 X 2.25" shock on my frame intended for a shock 7.78 X 2". Am i going to run into trouble here? Is this possible without killing my frame?
    ANYONE?
    Which frame? Might be a good idea to speak up - someone out there may already have tried and can save you some time and money if it didn't work out.
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  16. #16
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    No, it won't rub. I'm running a 2.5 Maxxis Minion on my 2.25" stroke Heckler and no problems.

  17. #17
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    Quote Originally Posted by endurofit
    "The shock really has nothing to do with the compression ratio, it's the frame design. If you are going to a longer stroke (in this case 2" to 2.25") with the same eye to eye (7.875"), then you are adding the travel to the bottom end. For the first 2" of the stroke the compression ratio is identical to what is was before, and keep in mind that it changes throughout the stroke. What the compression ratio is beyond that 2" depends on the frame design. On the Heckler, (falling rate design) the compression ratio gets higher as you go through the stroke, and the added .25" has a higher compression ratio than the rest of the stroke. On a bike with a rising rate design, it could very well be that the added .25" has a lower compression ratio than the rest of the stroke."

    What size tire are you running on your Heckler. I run a 2.35 Nevegal and want to put a 2.25 stroke on my Heckler-Would it rub on the ST? Thanks

    Brent
    A 2.25" stroke for the Heckler is fine, that's what they are often spec'ed with now. I ran a 2.35 Nev with no problems. You could even go a lot bigger. I ran into problems with the chain hitting the side of the tire (in my lowest granny gear) long before any frame clearance issues arose.

  18. #18
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    Quote Originally Posted by Bikinfoolferlife
    Where are the engineers when ya want one?
    Don't even say that...

  19. #19
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    So Kapusta what suspension design is the GIANT Maestro, falling or rising? Was thinking of trying something similar w/ my Trance.
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  20. #20
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    Quote Originally Posted by LyNx
    So Kapusta what suspension design is the GIANT Maestro, falling or rising? Was thinking of trying something similar w/ my Trance.
    I'm not sure, but If it is similar to a vpp design, then I would think twice about doing it. The reason I say this is that the vpp design relies on the rear linkage being in a fairly specific place in it's travel at sag and while pedaling.

    I'm not familiar with the Maestro design, so I don't really know if it is like vpp, I just though I'd throw that out there.

  21. #21
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    Quote Originally Posted by LyNx
    So Kapusta what suspension design is the GIANT Maestro, falling or rising? Was thinking of trying something similar w/ my Trance.
    I believe it is rising, though I am not sure.

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