You know the "series" number refers to the aspect ratio andJust my opinion,it's the tires. Back in the day if you owned an American muscle car,you ran wide tires.
I had 60 series tires on my early 70s Charger,i remember a guy in high school had an early 70s Challenger with 60s on the front and 50 series tires on the rear with air shocks,it looked sooo good!
It's one of the things i find annoying in the game,no option to buy wide tires,they do equip some cars with wide tires but not near enough.
More rubber on the asphalt means more grip,just sayin'.