Tires: conversion, split rims, tire sizing

Question
Barry,
     Hello,I hope you can help me out.I'm restoring a 1948 1 ton pickup,and having problems locating tires at an affordable price.The truck came into my possesion with 17" split rims, I have since located and purchased a very good set of hubcaps and cleaned the rims etc.The original tires were marked as 17x7.5.Would you please tell me what that converts to in "todays language".
   I can get original sized from Coker and a few others, but as I said earlier They would not be affordable.Also, I can't update the rims, they are 17" 8 bolt rims and those previosly mentionsed hubcaps won't fit.Any information you can provide would be greatly appreciated.
Thanks
Geoff

Answer
Geoff,

You are not going to like this answer.  But first I have to establish some critical data:

1)  I think you meant the old tire size was a 7.50-17.  This is a crucial point as tire sizing contains within its pattern of numbers, dashes, dots, and letters a coding that tells a tire engineer the particular tire sizing system that is being used.  So I hope the tire size you quoted - 17X7.5 - is incorrect.  If the tire size is not 7.50-17 then everything I am going to say is also incorrect.

2)  The tire is likely an 8 Ply Rating.  This is also an important point.

3)  The tire is a tubetype - another important point.

If all of this is true, then there aren't any modern equivalent tires.  There are 3 problems:

1)  All modern 17" tires are tubeless.  The rims you have REQUIRE tubes (and a flap).  

2)  The 17" tubes I found by searching the internet are designed for the old style tires and are too large in diameter to fit modern 17" tires. They would buckle inside and eventually fail in a sudden release of pressure - very bad accidents occur this way.

3)  The rim is too narrow and the rim flanges are too tall for modern 17" tires.  Not only would modern 17" tires arch across the tread face, but the sidewalls would prevent the beads from properly seating on the rim.  Not only would this be dangerous, but the vehicle would feel very unstable.

Sorry, but your best bet is to find a set of 7.50-17 8 ply rating bias ply tires (plus tubes and a flaps).  I did a quick search and was able to find some possible tires, but if Coker Tire is the only source, then that's the way it is.