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For the Pinto an inch increase in tire diameter  from stock will throw the speedometer off by about 3 mph.( assuming it is calibrated correctly to begin with). Using a speedometer gear with one less tooth will adjust for that. If the tire diameter is smaller than stock would want to go up in tooth number.
   Not to sound like a broken record( and someone correct me if I’m wrong) but your speedometer has no electrical input. There is no ground in the system. You have a mechanical problem.
  With regards to the turn signals corrosion at the bulbs/ sockets would be there areas where ground would most likely be a problem. Also consider a bad bulb. But your parking lights and emergency flashers might act the same way. If they work normally without the start stop you mention try swapping the emergency flasher for the turn signal flasher.

The tires are from Coker Tires, Maxxis WSW 175/80R 13; The original sized 165’s were impossible to find. What’s the size difference between 165 and 175s? I was told it was like a quarter inch…but I am thinking if those numbers are in metric, so that would be ten milimeters. That’s .39 inches if my math serves me correctly. Less than half an inch…would that make it 1.5 mph difference rather than your quoted three miles? Odometer Reading more or less? 🤔

Secondly, you made an excellent point about the Speedo being mechanical thus should be unrelated to the turn signals, which is electrical in nature…but oddly they stopped working until I restart the car. It hasn’t happened in the last couple of days as I am driving it more (it hibernates during the winter months). Fingers crossed that it was just a quirky thing that resolves itself…I know, I know…nothing resolves itself, but I can only hope! 🤞🏻

See y’all in Carlisle!!! Happy Motoring!

I wasn't referring to your specific tire situation rather a generic statement. Speedometer changes are due to changes in tire diameter not width. There are online calculators you can find to compare your old tire diameter to the new. There are also online calculators to figure what speedometer gear you would use. The size of the tires that were on your car when you got it may not have been what it left the factory with. If your speedometer reading is close ( like  within 3 MPH @ 60 MPH) to what you get when you check it against a GPS then you are good to go.

Awesome suggestion about the gps to compare against the Speedo! I will def do that as I may be worrying about nothing!

You are right…I don’t know what I was thinking when I typed the nbr was sidewall measurements rather than the width…chuckling…

The tire shopping measurements I used was taken off the car’s orginal price sticker, which proved the 165 numbers.

Happy Motoring!



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