What rpm at 65mph ???

Discussion in 'Questions From New Drivers' started by The Wiz, Jun 4, 2020.

  1. The Wiz

    The Wiz Bobtail Member

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    I have been reading many posts but still need help.
    I am looking to buy a 2016 kw t680 mx13 500hp, 18 spd manual, with 3.7 rear ratio.
    I am trying to find out what rpm it will turn at 65mph ,??
    I pull a dry van with 20-30k lbs.
     
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  3. The Wiz

    The Wiz Bobtail Member

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    Sorry 11R22.5 tires
     
  4. kelgar50

    kelgar50 Medium Load Member

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    Why would you want those specs if your not running heavy haul?
    Those are horrible specs no fuel mileage there.
     
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  5. The Wiz

    The Wiz Bobtail Member

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    That's what I'm trying to figure out !!! The tractor is a great deal... I'm trying to find out if it is worth the fight.
     
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  6. 062

    062 Road Train Member

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    Roughly 1410rpm. Google road speed calculator.
     
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  7. The Wiz

    The Wiz Bobtail Member

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    Thank you 062.
    Well at 1410 rpm, why would the fuel mileage be so poor ?
    Isn't this an ideal rpm ??
    And should be good on hills.
     
  8. lovesthedrive

    lovesthedrive R.I.P.

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    First off what engine? Detroits like 1500 rpm. Cats like 1200 rpm. Unknown for Cummins
     
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  9. 062

    062 Road Train Member

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    I never had any experience with the mx motors. @Long FLD runs one.
     
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  10. Long FLD

    Long FLD Road Train Member

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    At 65 you will be on the upper end of where you want to run the engine. The torque curve on the MX is low (1100-1400 rpm). If your plan is to consistently run 60 to 65 then it won’t be bad.
     
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  11. The Wiz

    The Wiz Bobtail Member

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    Mx13 500hp.
    I think that it is 2nd or 3rd gen.
    I currently own a 2013 Peterbilt 587 mx13 455hp, 13spd automatic, 3.42 ratio, 22.5 tires. I run 1300rpm at 65 mph but... it doesn't like hills or to much weight.
     
  12. SmallPackage

    SmallPackage Road Train Member

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    BC20FEDC-B6DB-496E-AD1B-EB415E56D9D9.jpeg
    Here is the formula.
    11r22.5=42 inch diam.
    11r24.5=44 inch diam. (These can be plus or minus a 1/4 inch by manufacturer and tire model )
    18 speed eaton top two gears.
    17th gear =.86
    18th gear =.73
     
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