i came across a set of brand new never use cup2 made in 2013 vs a set made in 2015 50% thread,
which ones would you choose and why?

TIA

 

Depends on how you plan to use them. If track, neither. Do you want to trust your car on 6 year old or half trashed tires with unknown heat cycles? Probably not a horrible thing but why take chances?

Point A to point B, Cup 2s on an occasional (dry weather) driver. But then again, if you're only streeting them, Cup 2s are a waste and could ultmately be hazardous in the wet and cold temps.

 

Mic has covered the basics on this. If these old/used tires are that cheap, than MAYBE they're a good stop gap. Otherwise, with the expected rubber compound degradation and outright wear, the money might be better spent on a new set of tires. BC is known for wet weather, and I'd look for a set of high-performance tires more suitable for those conditions if your Z is primarily a street car.