well if yr serious about roadgrip like me,, i think you chk out the road first i like do. , i sometimes take a walk on road to know what is left of it my shoes tell me about the road i walk on,, Pk roads some of them gone real bad as far grip is concerned. if yr tires wearing out,, then the softer part of tire rubber which helps with grips is going.
2ndly cars like boxsters 350z rx 8 dont get any grip,, , here is lil beyond tires, you just have to slow down in time to risk it too much.