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  1. #1
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Listen! The FrankenTurner Party Pack...

    Did a little measuring tonight. Below is a table with the data. All measurements were taken in millimeters to the nearest mm or in degrees to the half a degree. Measurements were taken in one direction, then the bike was turned 180 degrees and measured again, and the two results averaged to take irregularities or slopes in the floor into account. The values were then converted to inches. The lengths in mm are very accurate. The angles are probably plus or minus about 0.5 degrees.

    Travel results are actual and measured, not calculated based on strokes and leverage ratios. They are based on the difference in the rear wheel axle's distance to the floor with the bike placed upside down with the shocks extended, and with the shocks deflated/spring removed and the rocker arms pulled firmly against the frame with a bar clamp. This measures the vertical component of wheel travel. The wheel path's arc distance may be greater. Again, this was the average of two measurements.

    The bike's setup is with an '05 Z1 FR1 (538mm A-C) and 2.3" tires front and back. The two shocks used are a DHX Air 7.5 x 2.0" and a DHX Coil 7.875 x 2.25". This was done on a Horst-link equipped 6-Pack using stock the stock seat stay, and also with a 5-Spot's seat stay (which is about 1/2" shorter in length from the rear dropout to the rear rocker pivot). The resulting geometries are as follows:

    My video techniques can be found in this thread.

  2. #2
    Baked Alaskan
    Reputation: AK Chris's Avatar
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    Cool, what about the same measurements with the Spot rockers?
    The red couch has moved from Alaska to Florida...

  3. #3
    jrv
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    TS-

    Do you by any chance have pictures? I am curious to see what the bike and the different rocker angle looks like with the longer i2i shock.

    Thank you for posting this information, very interesting.
    -JR

  4. #4
    Lay off the Levers
    Reputation: Bikezilla's Avatar
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    Nice! Mix and match, match and mix, choose your config and get your fix.
    Faster is better, even when it's not.

  5. #5
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    Quote Originally Posted by jrv
    TS-

    Do you by any chance have pictures? I am curious to see what the bike and the different rocker angle looks like with the longer i2i shock.

    Thank you for posting this information, very interesting.
    -JR
    I agree, could you post pics, this is interesting. I guess I should do a search, it sounds like you've been discussing this for a while and I'm coming in at half time.

  6. #6
    It's a Turner!
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    Ok, so doesn't the 7.875 x 2.25 shock on the pack allow the seatstay bridge to come into contact with the seat tube?
    Last edited by sirbikesalot; 03-18-2006 at 06:49 AM.
    I didn't just drink the koolaid, I stuck my head in the punchbowl.

  7. #7
    FM
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    Quote Originally Posted by sirbikesalot
    Ok, so doesn't the 7.875 x 2.25 shock on the pack allow the seatstay bridge to come into contact with the seat tube?
    It would make sense that there is no interference, since the increase in stroke is less that the increase in i2i length.

    However, I bet their woudl be clearance problems between the rockers and bottom of top-tube, on smaller frame sizes.

    Very cool Tcheezy!

  8. #8
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    Seems like a perfect opportunity for a graph....;]

  9. #9
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    FM is correct, there is actually a bit more clearance at bottomout with the longer stroke (and longer yet i2i) shock. Running just the longer shock on a stock Pack kinda wacks the angles. Running the longer shock with the Spot stay brings things back in line for the most part. The cool setup is the Spot stays with the stock shock. That lowers and slouches the bike in a very pleasant way. The leverage ratio is the same in each instance since nothing in the overall linkage changes, and the travel increase is by definition proportional to the increase in stroke.
    My video techniques can be found in this thread.

  10. #10
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Quote Originally Posted by kelly1
    Seems like a perfect opportunity for a graph....;]
    An excellent suggestion.

    My video techniques can be found in this thread.

  11. #11
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    Quote Originally Posted by tscheezy
    The cool setup is the Spot stays with the stock shock. That lowers and slouches the bike in a very pleasant way..
    ...I have been pondering something along these lines. My overall plan is to have the TNT RFX chain stay & Spot seat stay assembly. This will allow a bit more tire clearance, beef up the "swingarm" where it needs it most & allow a slightly lower/ slacker geo. I am curious about the change in virtual shock I2I that comes as a result of the Spot stay swapout...if it was essentially .25", this would allow me to have a custom Avy done @ 7.75" x 2.25" & closely maintain stock geo while increasing travel a smidge. Of course I would lose the benefits of the lower BB & slightly slacker HA, but a worthwhile change nonetheless. The other consideration will be how much different the virtual I2I change will be with the given rockers (Spot vs. RFX).
    Last edited by jncarpenter; 12-22-2006 at 10:26 AM.


  12. #12
    Baked Alaskan
    Reputation: AK Chris's Avatar
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    Ts -- that's actually a really cool way of presenting the info, makes it easier to digest rather than looking at a chart. Who knew charts could be so useful? Then again its actual measured information, not a theroy from a motorcycle engineering book on what may be going on. Couldn't resist a shot at the faux engineers.

    Interesting how the seat angle changed pretty dramatically going from the Spot to Pack with the 7.5" shock, but very little on the 7.875" shock, despite the change in head angle. Since everything is in pieces on my end, I'm still curious what the differences are with the Spot rockers. The longer shock really jacks the BB up too, puts it in ID territory.

    The numbers with the Spot stays and the longer shock look pretty good to me, kinda like a really long travel Spot. If it maintain's the neutral handling of the Spot with all that travel and the higher BB, you may have stumbled on the ultimate trailbike setup. Nice work.
    The red couch has moved from Alaska to Florida...

  13. #13
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Chris- the front triangle angles should track each other perfectly. The fact that they don't indicates errors in measuring. It is the trend which is the important thing more than any single data point. Overall I have confidence in the numbers showing the correct trend, but I wouldn't take a single point as gospel. I have been riding the long shock and Spot stays for a few weeks now. Works great.

    JNC- I also considered the 7.75 x 2.25 Avy, but I'm not ready to invest that kind of $$ in an experiment. It would lower the BB by about 0.2-0.25" and that's about it (from the standpoint of geometry). Worth big bucks?? If I were buying an Avy anyway, I'd consider that route. Going from the linear coil to a progressive DHX Air with the RP3 sleeve would probably gain you that same advantage just in added sag. Or run a coil a tiny bit soft with more sag and increase the BO on the DHX.
    My video techniques can be found in this thread.

  14. #14
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    Quote Originally Posted by tscheezy
    JNC- I also considered the 7.75 x 2.25 Avy, but I'm not ready to invest that kind of $$ in an experiment. It would lower the BB by about 0.2-0.25" and that's about it (from the standpoint of geometry). Worth big bucks?? If I were buying an Avy anyway, I'd consider that route. Going from the linear coil to a progressive DHX Air with the RP3 sleeve would probably gain you that same advantage just in added sag. Or run a coil a tiny bit soft with more sag and increase the BO on the DHX.
    ...well, technically I'm not really interested in adding more travel (which is all the mod would really do). I am more interested in lowering the leverage ratio in 6" mode....but it's no real big deal. I will likely stick with the stock stroke length. Either way I plan to keep the DHXa for shorter travel/ lighter configs.


  15. #15
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Oh, I think I get it. You want to run a 2.25" stroke shock with the Spot 5.3 rockers (which give a 2.65:1 ratio), so that you end up with 5.95" travel. And combine that with the Spot stays for a slacker ride. Did I get that right?

    I was confused as I thought you were saying the longer stroke shock results in a lower leverage ratio, which it does not. The linkage determines the ratio, not the shock stroke.
    My video techniques can be found in this thread.

  16. #16
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    Quote Originally Posted by tscheezy
    Oh, I think I get it. You want to run a 2.25" stroke shock with the Spot 5.3 rockers (which give a 2.65:1 ratio), so that you end up with 5.95" travel. And combine that with the Spot stays for a slacker ride. Did I get that right?

    I was confused as I thought you were saying the longer stroke shock results in a lower leverage ratio, which it does not. The linkage determines the ratio, not the shock stroke.
    ...right on. I would prefer the solid rocker, however, ala circa 2002 RFX.


  17. #17
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    Bonking ... not feelin' well

    so being new to the rfx scene where do I get a set of spot stays and maybe even a longer swingarm...on a side note. How big is to big for the rfx? I am rethinking my decision a little maybe I should have gotten the highline...any highliners want to trade for an rfx?

  18. #18
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    You can maybe get Spot stays from Turner. Call them. A longer swingarm? The current RFX swingarm is the longest they make.

    Tell us what you want to do and maybe we can tell you if you or your bike will survive. El Chingon is a 240 pound dude and is not kind to his rig.

    My video techniques can be found in this thread.

  19. #19
    i want spring!
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    Tmtoyh

    somebody got to much time on ther hands. i wish the snow melts or stops snowing for your sake and this forum.

    Db
    Check out all these mountain biking t-shirts, hats, sweatshirts by Trail Hog today!

  20. #20
    No, that's not phonetic
    Reputation: tscheezy's Avatar
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    Do you watch TV?

    I don't.

    Ever.

    That frees up some time.
    My video techniques can be found in this thread.

  21. #21
    mtbr platinum member
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    Do they even have TV stations on Kodiak?

    I'd bet you'd watch if there were PBS documentaries on:
    "The History of Journal Bearings"
    "The Life and Prior Art of David Turner"
    "David Turner: The Battle of Pivot Location Nuances"
    "The Rise and Fall of The Big E: How Patent Numbers Improve Bicycle Ride Quality"
    I stopped driving my bike into my garage - I'm now protected with Roof Rack Ranger app for my iPhone.

  22. #22
    Amphibious Technologies
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    Some additional data

    6Pack stock config (7.5x2.0 shock):

    HA = 67.5
    BB = 14.25

    6 Pack with 7.75x2.25 shock; everything else stock:

    HA = 68.5
    BB = 14.875

    Fork A-C = 545mm +/- 2mm; 2.35" MHR rear tire; 2.7" MHR front tire; angle error ~0.5 degrees.


    Conclusion: a 0.25" (2/8") change in shock i2i = 1 degree change in HA and 5/8" change in BB height.

    Quote Originally Posted by tscheezy
    Based on all data above, a 1/8" change in i2i = 0.5 degree change in HA and switching from Pack to Spot seatstays results in a -1 degree HA and -0.7" BB. Thus 7.75 x 2.25 shock with Spot seatstays = Pack original geometry with more travel. But we already knew that from 'zillas post




    .
    Last edited by SCUBAPRO; 12-21-2006 at 12:06 AM.
    "The best you've ridden is the best you know" - Paul Thede, Race Tech

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