F70x14 Tires

[zerfetzen]

What does F70x14 mean?  I'm sure these are for 14 inch wheels, so the question is: what does F70 mean? 7 inches wide?  Any takers?

[resq302]

I could be wrong, but I think the F stands for how wide the tire is and the 70 is how tall it is.

[Ghoste]

The letter is more like a load rating and the 70 is the aspect ratio meaning the sidewalls are 70% high as they are wide in this case.

[zerfetzen]

Thanks, I never knew that 

[OldGuy]

Actually, the alpha letters determined the diameter of the tires in comparision with the width.  The nominclature was for bias ply tires.  There were four (4) letter ranges in the 60 and 70 series tires - E,F,G and H. The diameter of the tire increased as the letters went up (side wall height) thus reducing the revolutions per mile.   However, the wider the tires were (60 Series vs 70 Series) with the same alpha lettering, the smaller in diameter due to the increase in width.  The 60 Series were wider than the 70 Series (sorry, I don't know what the difference in width between the two series was).  So, if you wanted a wider tire - (60 Series) but the same diameter as a 70 Series tire for mileage, you would have to go up in the Alpha lettering in the 60 series (increase side wall height) - i.e. H60x14 was about the same diameter as a F70x14.  The 78 Series had a greater diameter range (A through J) but not as wide - Mom & Pop tires

example:

Tire Size          Diameter          Rev/Mile
E70x14            25.8               783
E60x14            24.8               814

F70x14            26.2               769
F60x14            25.3               798

G70x14           26.8               752
G60x14           25.8               782

H70x14           27.5               733
H60x14           26.4               764

I ran G70x14's on my 1968 Charger back in the day (1969-1971)

A good comparison chart can be found at  http://www.turbinecar.com/tires.htm

[zerfetzen]

Thanks OldGuy, great info!