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sm465, 4.56 gears - What size tires to run?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Taylor, Jan 21, 2005.

  1. Taylor

    Taylor 1/2 ton status

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    I recently bought a 74 k20 as a project truck, it has a 350/sm465/205 w/ 4.56 gears. What size tires should I be looking at? Normally I would think 4.56 gears = 35's, but without having an overdrive should I run something in the 36-38 range?
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    Depends on how fast you need to go and how many RPM's you are willing to have your motor reving at cruise speed. If you are going to pick a tire based on gears and RPM then pick your normal cruise speed and whatever RPM you want the motor to spin at. Plug it into the calculators and get the tire size that best fits.

    Eventually I will be running 35's or 37's with a 465 and 4.56's. I will just have to keep the cruise speed down to around 65 so I don't keep the motor to reved out and kill the gas mileage.

    I think 37-40" tires is about right for a 465 with 4.56's. The cruise RPM at 65 is roughly 2750 for 37's (36" true height) and about 2550 for 39.5's (38.5 true). If you want a higher cruise speed you will need to up the tires or spin the motor faster.

    Halrey
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Dude,,,you spelt your name wrong. :D

    I run a 465 with 4.56's and 39.5's. I could still use an overdrive, but I run the 6.2. It has no trouble spinning 2600 all day long, but I could pick up 2-4 mpg with an overdrive. With a small block I'd run 38-39.5's.

    Rene
     

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