I notice rears tend wear a lot more than the fronts.
I like the grooves as it appears to give even wear with very little scoring, as the grit has somewhere to fall in to.
I will spray tomorrow the disc hubs to protect them.
I just use some Plastcote chrome paint or just silver.
Keeps them smart and don't rust or burn off.
When you say the headlamamp lens has grazed, do you mean that it is cloudy?
I don't know if it is applicable to the Z4 and I have never tried it, but I have seen videos of people using a specialist very fine cream to grind off the very top layer and had very good results.
Can anyone else comment on this? Much easier and cheaper than replacing the lens, if it works. Thinking it through, if the lens still needs to be replaced, you haven't spent much anyway.