Anyone calculate/know the Motion Ratio?

Discussion in 'Tire , Wheel, Brake and Suspension' started by Stuntman, Jun 25, 2014.

  1. Stuntman

    Stuntman Enthusiast

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    Has anyone calculated the front and rear Motion Ratio for a Gen I/II to determine the wheel rates?

    My search has come up with nothing.
     
  2. TrackAire

    TrackAire Viper Owner

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  3. Stuntman

    Stuntman Enthusiast

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    Yes that is one way to calculate the MR. Another is to know your spring rate and add weight until it compresses an inch, or travel the tire an inch and measure how far the spring compressed. Any track people do this on a Gen 1/2?
     
  4. Stuntman

    Stuntman Enthusiast

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    Anyone, anyone? ...bueller?
     
  5. Dom426h

    Dom426h Viper Owner

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    No, we just trust that the engineers at Penske, Moton, and MCS know what they are doing. Buy their stuff, and rock & roll on the track. :drive:

    What are you trying to do Stuntman? Spec a custom valve job on a damper?

    If you have questions about suspension setup I recommend coming out to a trackday and talking with the competitive teams. NARRA is doing one at Sebring not too far from you in November.
     
  6. Stuntman

    Stuntman Enthusiast

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    New to the car and interested in the wheel rates of various spring packages and hoping the MRs are known so I don't have to measure it myself.

    Here's a few different spring rates I've found:

    250/450 stock
    325/500 Roe (325/550)
    400/750 ACR v1
    450/650 Woodhouse + my Gen 1 (1rst time)
    500/1100 OEM ACR v2
    500/800 what ACR owners liked better
    550/800 my Gen 1 now
    600/800 Verges
    700/900 NDW on Archer revalve

    http://forums.viperclub.org/threads...rates-for-street-driving.-Eibachs-are-going!?

    However I remember seeing that Gen IIs have 300/500 stock.
     
    Last edited: Aug 25, 2014
  7. Dom426h

    Dom426h Viper Owner

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    This is what I have on record for the Gen2:

    Front / Rear

    250 / 450 Stock
    400 / 750 ACR v1
    500 / 1100 ACR v2 (too stiff)(even for road racing some switched to 750-800 rear springs)

    Eibach spring rates:
    343 / 457-800 Progressive

    KW V2
    365 / 685

    MCS
    500 / 800
     
  8. Dom426h

    Dom426h Viper Owner

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    I am running the new(just came out in 2013) MCS Single Adjustable dampers with their recommended 500/800 springs.
    The setup feels money but I still have more adjusting & hard back road riding to do before writing up a review...

    I'm still wandering why your so concerned about motion ratio?
    IMO you should be more concerned about the dampening rates and overall design of the dampers... but you still haven't said what your after so it's kind of hard to give advice.
     
    Last edited: Aug 25, 2014
  9. Stuntman

    Stuntman Enthusiast

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    I'm just looking for the motion ratio to see what stock wheel rates were chosen for the car. At the end of the day you can't compare spring rates between various cars but wheel rates are apples:apples. Plus a 100lb change on the front will not be the same as a 100lb change in the rear. So knowing the MR will answer that.

    Having tracked and daily driven various setups on various cars and knowing the wheel rates of each, I would like to apply that knowledge to the subjective comments of various spring rate setups for the viper in terms or ride quality and balance.

    -just doing some HW before deciding on a good, soft trackable street setup.

    Please share your setup and comments.
     
  10. Stuntman

    Stuntman Enthusiast

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    Bump. The Motion Ratio is a very valuable piece of information if you have coilovers with a separately adjustable sprig perch and threaded body lower mount (Like BC coilovers) to determine how much compression and droop travel to run and where to set your spring preload.
     
  11. Tom S

    Tom S Viper Owner

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    You can jack up the car and make some measurements and calculate the MR. I'm going to do a suspension analysis once I get all the dimensions measured. Just for fun really- to see what how the stock balance comes out, and how aftermarket springs affect it.
     

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