[ohhawk]

Agree, very informative summary from mmrec. I worked for Goodyear for a couple of years during the early 70s when the Polyglas tires were making their entrance (during the time when Goodyear stores were selling everything including appliances). Most Polyglas tires at the early stage of release were certainly not RWL versions but primarily were black or W/S.

There is alot of misinformation out there as mmrec points out very well. Polyglas became a key ingredient on many Goodyear tires even though they weren't the RWL version that said Polyglas.

As I recall the benefit of fiberglas was in layman's terms to give you more miles from your tire. The two fiberglas belts along with the two polyester (some later used Rayon) gave the tire more stability/rigidity allowing the tread less squirm on the road = more miles per tire. Most mfg's at this stage used a 2/2 design of 2 ply fiberglas and 2 ply polyester. The polyester still gave the tire some give for purposes of riding comfort. An all polyester tire would give an even better ride but less miles per tire. I do remember that the fiberglas belted tires had ongoing problems with "cupping". You had to keep them balanced. Many drivers would come back after owning the tire for awhile and would have the cupping problem and would expect an adjustment for a new tire.....no adjustment would be given for this issue.

Believe you can still get the 15" Polyglas repro tires from Kelsey Tire.