Spare tire advise needed

[Gaurav]

15 minutes ago, Mario Cornejo said:

Would regular tire rotation help in the maintenance of the five tires? What is your view?

Yes ofc, only if you rem the order and frequency.

I thought the same in 2017 when I got 5 new tires, never rem after that.

[Looper]

16 hours ago, Thomas Varghese said:

Vulcanized rubber to get deteriorated takes a lot of time. I have read all the comments here. The reason for the tire to get cracked after years is due to ply separation. Rubber compound when masticated with chemicals to become a tire compound has oil also added to it. After years the oil starts to evaporate making the tire more brittle. Also when the tire is vulcanized in the tire mould the outer parts of the tire get more heat and vulcanizes more. The inner parts of the tire where the ply's are arranged are not vulcanized fully as heat reaches there less. So a tire which has aged is more likely to fail as the bond between the ply's gets weaker after years. Another reason is the addition of synthetic rubber in tires. Synthetic rubber is added to the compound to give it more abrasion resistance. But if u have stock of old synthetic rubber, you see that the tensile strength of the rubber has deteriorated a lot and if u pull it will just tear off. I can say this with 100% confidence as I had a rubber mastication unit which was handed over to me through generations.  

@gaurav I would keep the 50% tread life tire and throw the 6 year old tire in the garbage. 

The X-pert entered the scene. Thanks @Thomas Varghese for your invaluable insights.

I rotate all my five tires every 10k with almost clockwork precision - they get cleaned from inside and re-balanced. I do the rearward crossing as depicted in the chart below.