the bruce
Go Kart Champion
So Sonny, same question. Why do all the OEM's go with drilled rotors on all their high performance car's then?
LOOKS. That's it.
At least by 95 %. Keep in mind there are difference between 'drilled' and 'drilled'.
Porsche rotors have casted holes, most ones are drilled after casting which hurts
the structur of the cast iron and weakens the rotor.
Incorrect. I see a large amount of drilled discs on Race cars and track cars. That is only with Iron however. Indy and F1 cars have switched to carbon and thus have removed the drilled holes. Plus Open wheels cars obviously have 0 issues with receiving adequate airflow to the brakes.
Despite popular belief gasses are still produced by modern brake pads particularly in the rain. However this is due to the semi-metallic pads interacting specifically with Iron. This is more common on the higher performance street and track pads that most of us use that intend to go to a track. Thus with the development of C rotors they have now become obsolete.
As to the comment earlier that no professional racers use slots. NASCAR use them extensively. See photo below:
The most interesting rotor design now is the wave rotor. The RS5 is using this design on Iron rotors. If you opt for the Carbon though they disappear.
I cannot fully agree, mate.
By far most true race cars run slotted rotors (iron). I don't even know a serious
race car running drilled rotors.
Open wheel cars have similar cooling issues though.
Of course pads do produce gasses, but these surely can be removed through slots
sufficiently too. I also don't see any reason why pads should degass more in the rain.
There's just some film of water for the very first moment when you hit the brakes
and this film is also easily removed by the slots.
Even more most race cars use sintered pads which have much less gassing than the
pads most of us use.
The wave design which both RS4 and RS5 use is just looks and marketing. I'd prefer
Audi would make some proper brakes for the TT-RS which is known for it's weak
brakes due to bad rotor design (curved but not directional vanes, both sides share
the same type of rotor) instead of making such silly designs.
To be honest rotor design is a very complex task. Slotting and cross drilling is just
one (minor) point. Alloying of the iron, content of carbon, some amounts of copper
and molybdanium (on expensive discs), casting technology, heat treatment (as well
on expensive discs only), the precision of cutting and of course the design of the
cooling vanes, the design of the aluminium hub - this all is crucial for a really good
brake rotor. Surface machining is just one part of a long story.
I'd always prefer a cooler running 2-piece rotor with a sophisticated vane design
over a cheap standard disc with the latest kind slots and drilling.