Rear end ratio and tire size

Discussion in 'Transmission & Driveline Topics' started by Elliott Taylor, Jun 13, 2021.

  1. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    yes around 27" tall. On cars you can't really move things tooooo far unlike a truck. Basically if you go up 1" thats only moving your total mph 3% (give or take) so at 60 ...thats +/- 1.8 mph...not a big deal.
    On a truck that has 31" then you go to 36" ...that is a 17% jump...to + 10 MPH @ 60 (truck would be doing 70)
     
    Last edited: Jun 15, 2021
  2. Elliott Taylor

    Elliott Taylor Member

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    Considering you can't really move up too much in height like you say, would you also say going with a taller tire won't affect the rear end too much ?
     
  3. biker

    biker Veteran Member

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    No. Even a 2" taller tire will affect the overall ratio very little. You may notice a very slight difference when starting out in 1st gear if you have a manual trans, but an automatic with a properly matched torque converter wont even blink.
     
  4. Elliott Taylor

    Elliott Taylor Member

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    I actually have a manual, so I won't anticipate much difference. Thanks for the info!
     
  5. 74RAT

    74RAT Veteran Member

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    Rpm = (mph x gear ratio x final drive x 336) divided by overall tire diameter

    Don't forget the slip of an auto trans converter, when it's not in lockup.
     
    Last edited: Jun 15, 2021
  6. RTSE

    RTSE Member

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    I changed my diff ratio from 2.42 highway gears to 3.91 I had to run 17” wheels as I converted to 4w disc brakes with 13 corvette discs on the front. Still running a TH350, speedo is way out but am installing a 4sp overdrive auto so that should even it all out
     
  7. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    check out speedway for a speedo drive "fixer"....little gear convertor to fix your speedo..
     

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