speedo gear help (I have the pertinent info)

Discussion in 'Technical' started by ptpdub, Jun 6, 2020.

  1. ptpdub

    ptpdub Member

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    7 tooth driven gear, (I think) 3.80 gear set, 215/65r15 tires. wha t speedo gear (cable end) do I need? I have been reading other posts and still not clear on the answer.
     
    ptpdub, Jun 6, 2020
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  2. Shorty

    Shorty Member

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    This is the formula I used to calculate the difference between my original tires and the bigger tires we're installing now:

    #Drive teeth x Axle Ratio x Tire Rev per Mile divided by 1001 = Driven Teeth

    Here's an example: BFG 245/60R14 - Dia.:25.6, RevsPerMile: 813

    The math: 7 x 4.11 x 813/1001+ 23.36664335664336 or 23 tooth gear.
    I actually checked the accuracy of the speedometer with my Garmin and it was very, very close.

    You can get the tire rev per mile from Tire rack's site.

    Hope this helps.

    Bruce
     
    Shorty, Jun 6, 2020
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  3. Krazy Comet

    Krazy Comet Tom

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    Krazy Comet, Jun 6, 2020
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