Tire Sidewall Height

[ew1usnr]

" The tires used on the Sprint hardtop model are 6.5” x 13”. "


Does that indicate the tread width and wheel diameter?


What is the sidewall height of that size tire?

Thanks, Dennis.

[Jeff W]

Couldn't have said it better myself :

http://www.barrystiretech.com/tiresizing.html

[ew1usnr]

Thanks, Jeff.

6.5-13 overall diameter highway tread = 24.58"

Hmmm. I am trying to figure out the source of my speedometer inaccuracy.

I am running 175/80 tires (tread width mm / height aspect %) with a tread width of 6.875” and a sidewall height = 0.8*175 = 140 mm = 5.5 inches. With 13” wheels and 175/80 tires that gives an overall diameter of wheel (13) + tire (11) = 24". So, what I have is a little smaller than what was originally specified (24.58").


But, my speedometer reads 3 mph slower than my actual speed. My actual speed was calculated from a 24" wheel size and tachometer rpm plus observations of road side radar signs that say "Your speed is ..... " that were 3 mph higher than my speedometer. It is a puzzle that with a smaller tire/wheel diameter that my speedometer should be reading slower than actual speed. It should read higher.


PS: I really like the white roof on your wagon. My first car was 1963 four door Falcon wagon with a 170 and I still think that Falcons were the most nicely sized, styled, and designed station wagons that have ever been made. I love the roll down back window and the way the back seat flips around to make a flat surface and that the car has no blind spots. They are pure automotive perfection.

[Jeff W]

Thanks for the kind comment on the color. The White Roof was original color and the Blue (Ming Green actually) is fairly close - the intent was an exact match to original but there was some communication issues with the painter. It could have been worse I guess.

I think you can easily solve your speedo problem by increasing your tire pressure to approximately 75psi :ROTFLMAO: Don't forget your kidney belt.

[redfalken]

Have you tried changing the driven gear on the speedo cable? I adjusted my speedo vs. reality that way and actually found the gear I needed at the Ford dealer.

Here's info on what I did.

http://www.redfalken.com/pages/drivengear.html

[ew1usnr]

Hello, Kenny.

I compared the circumferences of the original 6" x 13" and 6.5" x 13" tires and concluded that the sizes were similar enough that that there would only be a 1/2 mph difference up or down between them and the 175/80 13 tires that I am using.

The speedometer gear must have been changed in the past with a gear that was slightly larger than the original (giving a slightly lower indicated speed).

Here are pictures of the gear that I took while my Ford-O-Matic was being rebuilt:

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