<VV>Tirez (overlapping Corvair)

[Padgett]

I'm not so sure that the letter series tires were only
>bias-belted designs.  I had at least three sets by different
>manufacturers (Atlas, Dunlop, and Goodrich) that were advertised (and
>marked) as radials.

My 78 Sunbird came with BR70/13 Firestone 500s, (the first to have major 
problems with separation) but all such had the "R" added, a plain letter 
G70x14 (70 Tempest) was Bias-Belted. Don't think that any letter tires were 
old style unbelted

The next change was to the P-metric and going out on a bit of a limb seem 
to recall that was an extension of the GM "TPC".  A brief abberation was 
the Ford (later also used by SAAB) TRX tire in the mid-70s-early 80s. All 
designations have overlapped for a while and changes in tires have never 
been sudden.

Padgett

Another slender branch is a memory that the first domestic car to make 
radials standard was the Lincoln Continental around 1970-72