I just got an 03 350z base with stock 18 enthusiast wheels. The car runs and drives great with the exception that recently it started slipping, grinding, "jumping" almost if you will, worse at higher speeds but it also does it going very slow with barely any pressure on the brake. I don't suspect susp. at all because it only happens while braking, not engine braking. Stock brakes, pads are okay looking, rotors are also great looking. I have the same size front tires but I got a nail in one not to long ago which lead me to discover that the idiot who had the car before me had the directional tires on backwards, so the front tires aren't great (same size but different tread levels). My driver side is dry rotted and cracked all over the place and I've heard from many drivers that tire separation from cupping (internal or external) can cause jumping and vibration through the brakes. I would like to know opinions and best guesses as to what the issue is, i'm mechanically inclined but will have to take it somewhere as I do not have a lift. I'm probably going to throw a new set of tires and wheels on it tomorrow being that was going to be my next mod to the car. if that doesn't solve the situation i'll probably have the rotors resurfaced and maybe replace the pads, inspect the master cylinder etc.. also this is my daily so i'm going to have to drive it as is for the time being and would like to know how bad of an idea that is.. haha