Anybody know what the bolts are on the front wheels that look like magnetic sensors or something?

 

Most likely they are wheel-balancing weights I would guess.

 

on the rotors, or on the wheels?

p.s. if you posted a pic i can't see it

 

Can't see w/o a pic, but you are probably seeing the studs that are there to prevent you from rotating the front/rear wheels on the Z. Because of the wheel stagger, they (Nissan) don't want you to swap front to back. Regards, Jim

 

What Jim said or it could be the tire pressure sensors (for those so equipped).

 

I had to take them out when I put in my privat fahren last week.

 

pic

 

That's the bolt to prevent the incorrect wheel thing. Pressure monitors are inside the wheel.... actually part of the air stem...