The Ford Barn

BlueSunoco · 02-18-2014, 11:02 AM

And no, it's not about the type of swim trunks Pluck wears.........

I also seem to recall (and not wanting to hijack Woodrow's thread) that as the Model A speedo ages, the magnet gets weak and the speed of the car is registering 'slow' so that when you think you are going 40 or 42 you may be booking along at 48-50.

I plan on testing my speed this spring against a modern car or the local cop's radar or some type of GPS. Anyone know of this? I guess maybe Bob would be the man to ask???

Christoph · 02-18-2014, 03:19 PM

Ja - its like you say .
1st and 2nd gear shows close to correct speed .
The faster you go the bigger is the difference between speedo and reality.

Mark in MT · 02-18-2014, 11:49 PM

After 80+ years the magnet can lose some of its strength, and the hair spring can relax some. It is not surprising that they off in calibration.

Another way to check it is to time how many seconds it takes to run between mile posts at a steady speed. Divide 3600 by the time gives speed in mph.

larrys40 · 02-19-2014, 12:10 PM

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A pretty accurate test within a mile an hour or two is Speed Box on my I-phone. I use it as a test now and then when driving the old cars and I am amazed at how accurate it is. It is a free app that can be downloaded and used. MPH or Kilometers.

For what it's worth.... I think it's a lot more accurate than pacing with a modern.. or expecting to get a reading from a radar gun... and it can be used anytime.
Larry Shepard

02-18-2014, 11:02 AM	#1
BlueSunoco Senior Member Join Date: Sep 2013 Location: Windy City Posts: 937	ANOTHER Model A speedo question And no, it's not about the type of swim trunks Pluck wears......... I also seem to recall (and not wanting to hijack Woodrow's thread) that as the Model A speedo ages, the magnet gets weak and the speed of the car is registering 'slow' so that when you think you are going 40 or 42 you may be booking along at 48-50. I plan on testing my speed this spring against a modern car or the local cop's radar or some type of GPS. Anyone know of this? I guess maybe Bob would be the man to ask???

02-18-2014, 03:19 PM	#2
Christoph Senior Member Join Date: Oct 2010 Location: Frankfurt am Main in Germany Posts: 671	Re: ANOTHER Model A speedo question Ja - its like you say . 1st and 2nd gear shows close to correct speed . The faster you go the bigger is the difference between speedo and reality.

02-18-2014, 11:49 PM	#3
Mark in MT Senior Member Join Date: May 2010 Location: Western MT Posts: 218	Re: ANOTHER Model A speedo question After 80+ years the magnet can lose some of its strength, and the hair spring can relax some. It is not surprising that they off in calibration. Another way to check it is to time how many seconds it takes to run between mile posts at a steady speed. Divide 3600 by the time gives speed in mph. __________________ Mark in MT Always looking for another opportunity to be wrong.

02-19-2014, 12:10 PM	#4
larrys40 Senior Member Join Date: May 2010 Location: St Charles , Missouri Posts: 1,998	Re: ANOTHER Model A speedo question Sponsored Links (Register now to hide all advertisements) A pretty accurate test within a mile an hour or two is Speed Box on my I-phone. I use it as a test now and then when driving the old cars and I am amazed at how accurate it is. It is a free app that can be downloaded and used. MPH or Kilometers. For what it's worth.... I think it's a lot more accurate than pacing with a modern.. or expecting to get a reading from a radar gun... and it can be used anytime. Larry Shepard