[ohhawk]

Not sure what the question is but.....

* E70 x 15 on a '69 Z doesn't sound right to me. Maybe I'm missing something with the title in your post. I usually associate this uncommon size to the Chrysler line for Dodge Demon / Plymouth Duster, back around this timeframe.

* Tire companies were going through lots of changes in late 60's into early 70's moving from nylon to polyester to fiberglass or a combo of each. Each material component stayed in most tire mfg.s lines for quite awhile. Nylon usually = affordable, polyester = comfortable ride, fiberglas belted = best mileage.

* Terms such as Vytacord, Polyglas, Supertread, Custom Cushion, were all brand names for each companies version of some of these compounds used in the tires. They all touted a different twist but it boiled down to nylon, rayon, polyester, fiberglass.

* Some of the RPO options in '69 show that you could get a 2 ply tire or the "new" fiberglass tires. The 2 ply might have been either all nylon or all polyester or 1 ply of each I don't know. All nylon tires were fast moving the way of the dinosaur at this point.

Don't know if this helps or not.