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Just wondering about actual speed,

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  • Just wondering about actual speed,

    I wonder how many actually know how fast they are going. Even with the correct gearing the speedos can be off quite a bit after all these years.
    Mine shows 43-45 at a GPS speed of 40 and 57 at a GPS of 50. [as long as I know I don't worry about it.]

  • #2
    Well, I know the speed I am traveling because I did adjust the gear ratio in the turtle to compensate for my smaller tires. I still need to adjust the speedo to get it a bit closer, but I'm just too damned lazy to pull the dash and adjust it until I have a real good reason to. And yes, I got the odometer as close as I cold with available gearing without getting too exotic with the gearing. I did need to build my own turtle so the smaller gear would match up with the worm, but then, I'm a machinist so that wasn't too hard to do. Now that I have tested it against the GPS it is just a matter of getting up off my lazy butt to finish the job, but it ain't my top priority right now.
    You wana look waaay far up da road and plan yer route because the brakes are far more of a suggestion than a command!


    • #3
      Take a look at the thread "And a Speedometer Question" started by WC Hall. If you have a round speedo, you can adjust the hair spring on top of the speed wheel to correct your MPH reading.
      Last edited by AL in NY; 02-11-2018, 03:20 PM.


      • #4
        i can tell you from experience it only takes a tiny tiny amount of adjustment of the hairspring to change the reading. I learned the hard way!


        • #5
          Mine was off in the tudor until I changed to 3.54 gears, and then it became correct. Just lucky I guess.

          Eastern Connecticut


          • #6
            There's a little trick to adjusting the hair spring. Move the speed wheel to the speed you are reading currently reading (44MPH) and note the position of the hair spring adjusting screw(let's say 4 to10 o'clock). Now move the speed wheel to the corrected MPH(40) you want the speedo to read. Look at the hair spring adjusting screw and move it to the position you saw for the 44MPH reading. Your speedo should now be calibrated.

            Sorry, I don't have any photos.
            Last edited by AL in NY; 02-11-2018, 07:46 PM.


            • BNCHIEF
              BNCHIEF commented
              Editing a comment
              Al that tip is a keeper, any pics of what we are looking at, would be a good tech section how to as well and thanks.

          • #7
            Why are you playing with hairsprings on the speedos? You are supposed to change the magnet air gap. I believe on some speedos that can even be changed from the back without taking it apart if you have the correct tools. I was working on some SW round speedos. I set up a motor drive with a counter so I knew input RPM and used one of the charts from Bob Johnsons website.



            • #8
              Kevin: the reason I posted changing the hair spring is because the fellow who rebuilt my SW round speedometer (Leonard Nickols) told me that is what I should change to correct small discrepancies in my MPH readings. Mr. Nichols is a noted speedometer rebuilder so I did what he suggested and my now speedometer reads dead on, not 3 MPH high.
              Last edited by AL in NY; 02-13-2018, 11:11 AM.


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