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  • Speedo tech question

    Setup is
    Aspire motor and 5 speed trans,
    Festy body and speedo,
    Tires are 205/60-13

    Trying to double check the speedo,
    What size tire did the aspire have?
    I checked it with an iPhone gps mph app
    and it seems dead on, but just doesn't
    Feel right.
    Any way to figure this out with math to double check?
    Last edited by Occhty; 09-12-2010, 10:14 PM.
    (paperboy 23) 88 Festy Blue, aspire Engine/trans/efi swap,

  • #2
    Know anyone with a GPS ?
    sigpic
    The Don - Midwest Festiva Inc., Missouri Chapter

    Link to my festiva pictures below
    https://fordfestiva.com/forums/album.php?albumid=10
    Celebrating 25 years of festiva(s) ownership.

    Comment


    • #3
      stock aspire tire is 155-80-13. 205-60-15 is WAY to big, you need a tire between 21.7" and 22.4" tall. your 205s are 24.7" tall. you should drop to a 205-45-15 to get it right. or better yet, a 195-50-15 as that size is within .1" of factory Aspire. or even 165-60-15 (exact same size).
      Last edited by FestYboy; 09-12-2010, 10:22 PM.
      Trees aren't kind to me...

      currently: 2 88Ls (Scrappy and Jersey), 88LX, 90L(Pepe), 91L, 91GL (Skippy) 93 GL Sport (the Mighty Favakk), 94 (Bruce) & 95 Aspire SEs, 97 Aspire (The Joker),
      94 Justy 4WD, 87 Fiero GT, plus 2 parts cars. That's my fleet.

      Comment


      • #4
        I do not think he has an Aspire.....I think he took an Aspire engine and tranny and put it in his Festy. If that is the case I believe the gearing in the Festy speedo/tach takes care of gearing differences and makes it 155/80/12's as the right size tire to make the speedo read right.
        "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


        • #5
          Thanks!

          I like the biggies, I'll just compensate 

          Yes, aspire motor and tranny.

          Festy body and speedo cluster.

          Fetyboy I must have did an edit while you were replying
          tire size I'm running is 205/60-13.

          Sorry
          (paperboy 23) 88 Festy Blue, aspire Engine/trans/efi swap,

          Comment


          • #6
            ah that makes a BIG differance lol. that's the equivilant to 185-60-14 that i run on Scrappy, and he's dead accurate (speedo - GPS - radar signs). so just keep doing what you're doing!
            Trees aren't kind to me...

            currently: 2 88Ls (Scrappy and Jersey), 88LX, 90L(Pepe), 91L, 91GL (Skippy) 93 GL Sport (the Mighty Favakk), 94 (Bruce) & 95 Aspire SEs, 97 Aspire (The Joker),
            94 Justy 4WD, 87 Fiero GT, plus 2 parts cars. That's my fleet.

            Comment


            • #7
              My thoughts are
              Aspire 155/80-13, 155/25.4*0.80 = 4.88*2+13= 22.76 in
              Tires 205/60-13, 205/25.4*0.60 = 4.84*2+13= 22.68 in
              .76-.68= .08 inch difference.

              Is this the correct formula?
              (paperboy 23) 88 Festy Blue, aspire Engine/trans/efi swap,

              Comment


              • #8
                Should be a little different....I believe I had the same size on a car once and they were off by a couple mph....

                Tire Size Comparison

                Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
                155/80-12 4.9in 10.9in 21.8in 68.4in 927 0.0%
                185/60-14 4.4in 11.4in 22.7in 71.4in 887 4.5%
                "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 Occhty View Post
                  My thoughts are
                  Aspire 155/80-13, 155/25.4*0.80 = 4.88*2+13= 22.76 in
                  Tires 205/60-13, 205/25.4*0.60 = 4.84*2+13= 22.68 in
                  .76-.68= .08 inch difference.

                  Is this the correct formula?
                  Tire Size Comparison

                  Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
                  155/80-12 4.9in 10.9in 21.8in 68.4in 927 0.0%
                  205/60-13 4.8in 11.3in 22.7in 71.3in 889 4.2%
                  about the same as Arty
                  "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


                  • #10
                    ^ yeah Willie i've seen those numbers before, and i can attest to the factory tires being too small via GPS. just bought a rust free running Auto for $30 (yes that's thirty) and on my trip to Sandman's place i observed a 4mph differance at 60 mph (GPS said 60, speedo said 64).
                    Trees aren't kind to me...

                    currently: 2 88Ls (Scrappy and Jersey), 88LX, 90L(Pepe), 91L, 91GL (Skippy) 93 GL Sport (the Mighty Favakk), 94 (Bruce) & 95 Aspire SEs, 97 Aspire (The Joker),
                    94 Justy 4WD, 87 Fiero GT, plus 2 parts cars. That's my fleet.

                    Comment


                    • #11
                      Originally posted by FestYboy View Post
                      ^ yeah Willie i've seen those numbers before, and i can attest to the factory tires being too small via GPS. just bought a rust free running Auto for $30 (yes that's thirty) and on my trip to Sandman's place i observed a 4mph differance at 60 mph (GPS said 60, speedo said 64).
                      I think we, not you but others, have discussed this and thought that maybe the year made a difference. I have had 3 90's cars with the 12's on them and had the gps in each and at any given speed the gps and speedo was exactly the same. Not sure where all the differences lie but it is only a couple miles an hour we are talking and does not really make that big of a difference. I think it best for anyone to check there own set up and use the info accordingly when calculating mpg and mph.
                      "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


                      • #12
                        Okay, but wouldn't the aspire trans be setup for
                        13s ? The only festy part would be the speedo,
                        Soo, would I have to calc the speedo relative to the
                        Tranny and then the tires?  lol
                        (paperboy 23) 88 Festy Blue, aspire Engine/trans/efi swap,

                        Comment


                        • #13
                          Originally posted by Occhty View Post
                          Okay, but wouldn't the aspire trans be setup for
                          13s ? The only festy part would be the speedo,
                          Soo, would I have to calc the speedo relative to the
                          Tranny and then the tires?  lol
                          no....the trans are the same except for actual gearing. The speedo takes care of the difference for the car. When it is in a Festy the trans will read correct with the 12's. When it is an Aspire the Aspire speedo makes up for the 13's.
                          "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


                          • #14
                            yeah, speedo gear ring on the diff is the same for both cars, so go with the tires that match the cluster you are using. and test test test!
                            Trees aren't kind to me...

                            currently: 2 88Ls (Scrappy and Jersey), 88LX, 90L(Pepe), 91L, 91GL (Skippy) 93 GL Sport (the Mighty Favakk), 94 (Bruce) & 95 Aspire SEs, 97 Aspire (The Joker),
                            94 Justy 4WD, 87 Fiero GT, plus 2 parts cars. That's my fleet.

                            Comment

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