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Speed Potential Calculator for Ring Gear and Pinion Changes

Discussion in 'The Hokey Ass Message Board' started by RoadkillCustoms, Feb 23, 2010.

  1. RoadkillCustoms
    Joined: Jul 10, 2008
    Posts: 270

    from Mesa, AZ

    This calculator is designed to give the potential speed values of a vehicle, based on the RPM of the engine, the ring gear and pinion gear ratio, the final transmission gear ratio and the tire diameter, ground to top of tire as mounted.

    The default values are for a typical V8 small block Chevrolet vehicle, however you may enter any value you wish. The default values yield a highway cruise speed of about 65 MPH. The higher the RGP ratio, the lower the top end speed but faster acceleration and more pulling power. The same is true of the transmission final gear ratio. The higher the engine RPM, the greater the potential speed at the cost of fuel, heat, friction and engine longevity. Although there is a point of diminishing returns, the larger the tire diameter, the higher the potential speed.

    Try the Speed Potential Calculator for Ring Gear and Pinion Changes
  2. Pete1
    Joined: Aug 23, 2004
    Posts: 2,091

    from Wa.

    That's a good one.
    Not portable like an Isky Dream Wheel though.
  3. RoadkillCustoms
    Joined: Jul 10, 2008
    Posts: 270

    from Mesa, AZ

    I hear ya, those little guys are pretty handy - I've got one in my tool box! I am working on a mobile and smart phone version of this however... I'll keep you posted!
  4. torchmann
    Joined: Feb 26, 2009
    Posts: 787

    from Omaha, Ne

    That's pretty smart, I like it.
    an easy way to compare changes once you figgure your parameters is...

    If you change something and can calculate the % of how much you changed it...
    That % will relate to the new proportions.
    If you change your tire's circumference or diameter 25% then the rpm's and miles/hour will also change 25%.
    if you know the % change in anything that's mathematically and linearly proportional then the same % change applies to every other factor in the equation.

    assuming that my odometer is correctly synchronized to my speedometer...
    If I drive 10 miles recording my odometer reading and noting the mile marker, the tenths of a mile difference between my odometer reading and the actual 10 miles by the milepost is the % that my speedometer is off.

    If I note my Odometer and it's at 34,400 miles and 6/10 when I passed a milepost I picked to start from...
    And I drive 10 miles (at any speed) by watching the mileposts...
    and my odometer now reads 34,410 and 7/10 then I know my odometer is 10% fast so when It reads 33mph, I'm actually doing 30 and when it reads 88 mph I'm actually doing 80.
    Notice how at 30, it's reading 3mph too fast and at 80 it's reading 8mph too fast.
    Weird huh?
    Didn't you always think if your speedo was 5mph fast at 55 it's 5mph fast all the time?
    It isn't when you do the math.
    The amount of difference it's off cannot stay the same in miles per hour. the mph difference changes at the same rate or % that the speedometer is off per mile.
    That stuff is what tickles my brain and a hotrod get's it all cooking.

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