Grooved and drilled discs are to help expel brake dust more easily under heavy breaking so that it does not get stuck between pad and disc and impair braking. I don't think it makes much if any at all difference to cooling. If you have some oil and dirt on brakes it will start smoking at 200C-250c and that's nothing for brake discs. If you get the discs glowing in the dark 600C+ then you need to start worrying. Anyway you might want to check that calipers/pistons are not binding.
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Currently 8less
2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D
8 history:
2006 A8 Sport 4.2TDI quattro SOLD,
1997 S8, reached end of life with gearbox failure
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