Calibrating a speedometer

c300g

c300g

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I live up in Canada where the speed limits are all in kilometers instead of miles. My 65 Savoy speedometer is in miles. I am terrible at judging my speed and need to rely on the speedometer. Its one thing to go with the flow of traffic but when there are minimal/no cars around I could be doing 100 in an 80 and I wouldnt notice.
I've been told that these old speedometers are very inaccurate to begin with so I was thinking about driving next to a friend with a new car, have him yell out the actual speed, compare it to my speedometer and record it. then make sticky notes with the correct speed in metric. This however will look really messy and definitely wont last. I'd much rather have the change made mechanically. Can anyone tell me if it is possible? Again, I am referring to my 1965 Plymouth Savoy (Fury).




1965 plymouth savoy .jpg
 
The quick conversion is MPH is 5/8 of KPH. Multiply the posted speed by 5 and then divide the product by 8.
If you can do the math in your head, it gets you close enough.
Example: 100 KPH =62 MPH

Another alternative is a GPS like a Tom-Tom or Garmin. Their speed readouts are pretty accurate. A smart phone with a speed app would work too.
 
Back in the day when metric hit Canada, the solution was a sheet of red stickon dots, in various colors and about 1/4" in diameter. You just stuck them on the speedo cover plastic. The worked, but weren't pretty. To day search eBay for mph to kph stickers and you'll find a pile of them. You can stick them on the cover or open the speedo and actually make your own custom gauge face. I cheated on my Fury, I bought a metric speedometer from a European Mopar.
 
I use the conversion of 1.6 to figure out the MPH to KPH conversion. Take 50mph and times that by 1.6....80kph....or vice versa.

Has your rear gears, and/or transmission been messed with? Are you running the correct diameter tires compared to the factory units? You can find speedo gear/tire size charts on the web that can help you dial in your speedo with the correct speedo gear in the tranny. Then there is the inherent error in the speedometer gauge itself....which is a little tougher to over come. If you get the right speedo gear to correspond with your chosen tire size and you are still finding that the reading on the speedo is incorrect you can fix this error with a ratio adapter between the speedo cable and transmission speedo gear assembly.

There is a company....PATC that can build a ratio adapter in various ratios to correct for this error.

Here is a thread I wrote up on how I did this for my 84 W350 crewcab with a cummins conversion.....

1stGen.org • View topic - Speedometer ratio adapter...
 
Lobby your government for a return to the English standard, or start a movement to seceed from Canada based on measurements.

It's as good a reason as language.
 
Carmine said:
Lobby your government for a return to the English standard, or start a movement to seceed from Canada based on measurements.

It's as good a reason as language.
Click to expand...

Don't get me started....this is the worse combination of Federal and Provincial gummints since Confederation. Not since the last Turdo was in power has Western Seperation reared it's head out here. BTW it's actually kinda fun watching new to Canada Americans drive down the freeway at 100MPH likes it's the Autobahn rather than a sedate 100KPH. In response to the OP I use an app on my Iphone to check my speed at the usual checkpoints
50kph
80
100
120
150
200 :)

I then REMEMBER my math and convert MPH to KPH plus/minus any differential from Iphone. You'll never see stickons on my car but nifty move Bill getting a KPH speedo outta Europe.
 
Being Canadian too I have Kilo speedos sourced from Europe (Finland and Norway) in both my cars too (66 Monaco which in Canada yses Fury dash and speedo and 66 Chrysler T&C) - they're out there but hard to find.

Bill is a copycat as I had mine first

I even converted my T&C Autopilot dial to KMs - and just finished making a custom KM dial for my Monaco Autopilot - a long story for another thread.
 
I just used my GPS, the Garmin has a dashboard more with large digits for the speed.
The speedometer didn't work on my Other Polara so this was the ticket.

Alan
 
The speedometer is linear so you should be able to change the gear in the transmission to get it to read correctly for you.


Alan
 
The old speedos were rarely accurate, close maybe. I judge speed with mile marker posts, one minute is 60 MPH. Note the 1/10th number as you reach a marker and again after ten miles to measure accuracy. Should work for kilos too.
 
thrashingcows said:
There is a company....PATC that can build a ratio adapter in various ratios to correct for this error.

Here is a thread I wrote up on how I did this for my 84 W350 crewcab with a cummins conversion.....

1stGen.org • View topic - Speedometer ratio adapter...
Click to expand...

Great information. With my current tires my speedo is around 5 mph off at 60. I gave the guy a call. He said if you want one for your car, take GPS readings at 40, 50, & 60. Recording the speedo readings at those speeds, then he can make an adapter. I believe he said cost was around $80 to $120.
 
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