My '66 Mustang has old 2 ply polyester + 2 ply fiberglass 14" whitewalls and has been garaged for about 4 years. Do these old tires develop flat spots like the radials. The tires show no cracks or signs of weather rot.
Actually the old technology tyres have more problems with flat spots.
However that is not really the problem here. They don’t make many bias ply tyres these days. Just how old are those tyres? Having them out of the sun helps, but it certainly does not stop aging of the tires. If they were my tyres I would not want to drive any faster on them than in a parade following a group of old women using walkers.
Agree with Joseph; these tires are about 25-30 years past their “best before” date! Bias-belted tires came out as a stop gap before manufacturers geared up to make radials. They were a poor compromise. Many were recalled. The rubber on yours is probalby nearing the end of its normal life.
Please drive slowly with these tires and replace them as soon as possible with something better. Even the cheapest radials from Walmart are light years better than what you have on there now!
One other possibility: These are reproductions.
Coker Tire does indeed supply reproductions of PolyGlas tires.
Will these flat spot after 4 years? - Yep!!
Nevertheless, you should check the date code. Anything older than 6 years starts to become suspect.
You have it exactly reversed. Radial tires do not “flat spot”.
What you are referring to is characteristic of NON-radial tires.
If those tires are as old as I suspect they are, you would be well advised to replace them.