Technical question about tires...a little guidance

Hey all, I have a question about tire sizes. I am currently running g-78 15 wide white tires on my 59 chevy apache. I want to swap over to radial wide whites and I am getting confused. Some of the tire folks say I need to convert to a 215 75 r-15, others say 225 75 r-15, and one dealer says 215-70 r15. The rims are stock 5 1'2" wide and in great shape. I'd like to fatten up the tire a bit but don't want to increase the height any. I'll be selling these g78's when I swap as well, nice looking but the ride is not all that good. I appreciate it.Thanks,
Lee

 

Tire SizeOverall DiameterSection WidthLoad Capacity
G78-1528.0"8.4"1,620 lbs @ 32 psi
G70-1527.5"8.6"1,620 lbs @ 32 psi
G60-1526.4"9.7"1,620 lbs @ 32 psi

To convert Alpha Numeric tires to P-metric sized tires, it is important to identify the original tire's aspect ratio. The 78-series Alpha Numeric tires should be replaced with today's 80-, or 75-series tires. If the vehicle was equipped with the low profile 70-, 60- or 50-series sizes, the P-metric substitution should be selected from the P-metric size column that offers the equivalent aspect ratio as the existing tire.


G78-15
27.8"
= 215-75R15
27.6"

These figures are from two different sites. Note that they are not exactly the same specs.

 

Try these two sites, they may be able to help you some:

http://www.rimsntires.com/specspro.jsp

http://www.turbinecar.com/tires.htm

 

Just my $.02
Sounds like a tiny tire for a pick-up!
Just for refferance.
Different manufacturers have different diameters for the same "size" tire.
Check out the actual dimensions of the tire sizes before you buy any, you will see some
very different diameters for the same size with different brands.
Good luck.

 

I explained how to calculate metric tyre dimensions here.

If you want to keep the 27.8"-odd height and add a bit of width, using that formula gives a suggestion of 235/70R15, which is 28" tall with a 9¼" section width.

Of course you could go for a 325/50R15, which has the same height but is 12.8" wide ...

Also, what Tony Martino said. The formula is useful, but the results need to be confirmed either by the manufacturer's figures or a tape measure.

 

thanks fellas...lots of good advice here.