z rated is the speed rating of what the tire can handle. I don't remember what the stock one are? but a z rated tire is good for 149+ mph. Ive never bought anything under a z rated tire to be honest. The tires i just picked up are y-rated. Good for 186+ mph. Will i ever hit that speed in my genesis? no.

also the speed rating doesn't determine how long the tires will last.. You want to look at the tread wear. My current tires are like a 220? which is very low. If you want them to last longer, but something around a 400..

 

Aw ok. So its the tread wear you look at. The stock tires are 180 which I am assuming really suck?

 

The lower the tread rating the better the grip but the shorter the life. The higher the tread rating the longer the life but worse grip (easy to figure out because softer tires grip better but also wear away faster).

Speed rating is the speed at which the tire is rated to not fail with a standing wave in the sidewall at that speed for one hour. If you don't plan on going over 100mph you can get much less rated tires, but most sellers won't sell it to you because if the car is capable of XXX speed, they have to sell tires rated for that speed.

 

So what is a good balance of tread wear vs grip? 280-300? The OEM ones are 180 so I assume they are not going to last very long.

 

Older tires have lower tread wear rating than newer tires as well as the newer tires having more grip.

Example: Pilot Sport PS2 (220) or RE050A (140) vs Pilot Super Sport (300) or Continental ExtremeContact DW (340)

 

Stock 19s are Y rated. If you go somewhere to get them mounted they probably won't put anything on but a Y rating.

Stock 18s are V rated.