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trading up to 13" tires

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  • trading up to 13" tires

    Question: If i go to 13" rims and wheels, how does that effect the reading of speedometer
    Thom-Lifes too short, don't blink
    93 Festiva (Little Red Truck)
    01 F-150 (Big Red Truck)

  • #2
    I put 155-80-13's on mine and by the GPS , i'm 1 MPH off on my speedo.
    1960 willys pickup
    1967 jeep cj5

    1988 festiva
    1989 festiva
    1990 festiva for parts
    1991 s-10

    "Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote!" —Benjamin Franklin, 1759

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    • #3
      try this calculator


      BP Festiva http://www.cardomain.com/ride/723319 - SOLD
      BPT Festiva www.cardomain.com/ride/2260009 - SOLD
      BPT GTX www.cardomain.com/ride/2436495 - SOLD
      New GTX - http://www.cardomain.com/ride/3294846/ - SOLD

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      • #4
        Putting 155r80/13s gives me a 5mph error per several Radars.

        David

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        • #5
          well according to the calculator that Matt posted....

          Actual Speed:60 mph 100 km/h , the differance in the two Speedometer1: 57.3 95.6 Speedometer Difference: 4.596% too slow Diameter Difference: -Diameter Difference: 4.4%
          Last edited by GenevaDirt; 11-01-2008, 09:08 PM.
          "FLTG4LIFE" @FINALLEVEL , "PBH"
          89L Silver EFI auto
          91GL Green Auto DD
          There ain't no rest for the wicked
          until we close our eyes for good.
          I will sleep when I die!
          I'm a little hunk of tin, nobody knows what shape I'm in. I've got four wheels and a running board, I'm not a Chevy, I'M A FORD!

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          • #6
            ^^^you've got something else wrong. The rolling diameter is only 1/2 inch different (vs 155R12), which should yield only a 2-3 mph error at 60 mph. Considering the Festy (as well as most other vehicles) has a built in error of positive 2-3 mph (reads 2-3 mph faster than actual) at 60 mph, the 155/80/13 should correct the speedo to within 1-2 mph. If you're getting nailed for 5mph over you either have a significant error in the speedo head, or the tires are mis-manucatured/mislabeled size.
            Jim DeAngelis

            kittens give Morbo gas!!



            Bright Blue 93 GL (1.6 8v, 5spd) (Hula-Baloo)
            Performance Red 94 Aspire SE (Stimpson)

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            • #7
              It's a bit of a moot point, but Festivas originally came with 145/r12s, so everyone rolling on 155/r12s would already be off on both the speed and the distance. I believe when I had my 14s on the Batstiva, that calculator said I was off about 6 or 7 mph. Something to think about when I rolled past the cops doing "60 in a 55"

              Dumb thieves go to prison, smart ones go to work for the Government.

              1988 L - 232K miles Batstiva
              1989 L - 247K miles Slick
              1990 L - 281K miles Orphan Annie
              Let the hoarding begin!! :mrgreen:

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              • #8
                I have the 155's on my car and according to my GPS...it is exact on...I have watched it since I owned the GPS and if I gain or slow by 1 mile per hour....so does the GPS.

                Just my observation.
                "FLTG4LIFE" @FINALLEVEL , "PBH"
                89L Silver EFI auto
                91GL Green Auto DD
                There ain't no rest for the wicked
                until we close our eyes for good.
                I will sleep when I die!
                I'm a little hunk of tin, nobody knows what shape I'm in. I've got four wheels and a running board, I'm not a Chevy, I'M A FORD!

                Comment


                • #9
                  Originally posted by batstiva View Post
                  It's a bit of a moot point, but Festivas originally came with 145/r12s, so everyone rolling on 155/r12s would already be off on both the speed and the distance. I believe when I had my 14s on the Batstiva, that calculator said I was off about 6 or 7 mph. Something to think about when I rolled past the cops doing "60 in a 55"
                  They also had optional 165/70/R12s
                  Jim DeAngelis

                  kittens give Morbo gas!!



                  Bright Blue 93 GL (1.6 8v, 5spd) (Hula-Baloo)
                  Performance Red 94 Aspire SE (Stimpson)

                  Comment


                  • #10
                    True, but if I remember correctly the sticker inside the door on mine called for 145s, which, for the record, were never on the car the whole time I owned it.

                    Dumb thieves go to prison, smart ones go to work for the Government.

                    1988 L - 232K miles Batstiva
                    1989 L - 247K miles Slick
                    1990 L - 281K miles Orphan Annie
                    Let the hoarding begin!! :mrgreen:

                    Comment

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