For long tread life, I run 235/60-14s on a 7.5" wheels at 28psi. Nice ride, and reasonably stable cornering around town, once you get used to the sidewall roll.
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On the back I run 295/50-15s on 10s, but the wheels are not quite wide enough. For long tread life, I have to run down at 24psi.
Again, nice ride, but it took a lil getting used to how they corner when pushed.
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BTW
The 60s Nomenclature was that a G had a tread width of 8.25 inches. This does not translate to metrics which are a profile measurement.
Depending on your wheel width, a G could be any profile width from 8 to about 11inches.
At 8 inches it would be a 225,
But at 10.75 it would be a 275.
The factory wheels on 340 cars was a 5.5Rally. This will accept a metric tire of around 205 to 225, with the sweet-spot being a 215
For freedom from wandering, the tire height should be very close to the factory height.
340 cars wore E70-14 which has a theoretical height of around 24.5 inches, and so the tire becomes 205/65, or a 215/60, or a 225/55
If you don't have a 5.5 wheel, then none of this is correct.
If your current 235/60-14s are wearing nicely across the face of the tread, then take one off, lay it flat, and measure across the profile. Convert the standard measurement to metric, and that is what you want to purchase. Say you measure 9.25 inches; then
9.25 x 25.5(the conversion factor)= 235.
the minimum wheel size is 70%, and a typical best performance wheel-size is 85%, so then your wheel size should be from 6.5 to 8.0, making 7.25 the sweet-spot. So then pick whatever gets you closest to a 24.3 tire height.
I'm not sure if you can run a 14x8" wheel on a 73, @ zero-offset. That would be a back space of 4.5, and Ima thinking a 14 inch steel wheel, will rub on the UBJ, and/or tear the clip-on wheel weights off. At least, on my 68 that is what happened. which is why it now wears 7.5s.
