S8, why no drilled disks

[craigw]

Saw a new S8 last night, love them, V10 engine but no drilled brakes? surpriseing I thought.

[16610LV]

craigw said:

Saw a new S8 last night, love them, V10 engine but no drilled brakes? surpriseing I thought.

Drilled discs are structurally a bit weaker, especially for such a heavy car. Grooved discs much stronger, with almost as efficient cooling.

[craigw]

ah ok, interesting, these just looked like conventional disks though.

[Plotloss]

Assuming due the weight of the car and the structural issues with drilled discs that solids are a better choice for the application.

[clubsport]

I am sure Porsche use drilled discs partly for aesthetics on their cars across the range, many of the after market replacements are solid/slotted, I think huge drilled discs would look too bling and attract too much attention on the S8....good move by Audi I think.

[clived]

I would doubt it Porsche used drilled discs. I'd suspect the holes are cast.

[clubsport]

clived said:

I would doubt it Porsche used drilled discs. I'd suspect the holes are cast.

Yes, you know what we mean, would cast discs with holes in them have made sense within this thread?

[oilchange]

dont know if this is the case everywhere but all the racing discs i've ever seen were grooved or flat, not drilled.

Audi developed Carbon Ceramic brakes as a upgrade option for the S8 so they didn't put much work into the standard brembo items. the S8 is a really heavy car and so generates a lot of heat under braking which if the discs were drilled would risk cracking (which has happened on the murcielago). Heat disspation is not really a problem on carbon ceramics as they work best at higher temperature which is less likely on a road car. Supercar makers that drill their discs still tend to do so for maximum braking performance, but that means the discs have a very short service life which would be a big problem for a long distance mile cruncher like an S8. on most supercars discs can last as little as 20K before cracking and are very expensive to replace, given the 20K a year and more average s8 mileages they have to last longer. if you want outright stopping power get the carbon ceramics, when i test drove a new S8 i nearly put my passenger through the windscreen.

Technical explanation from AP racing:

Grooved discs.

1. grooves clean the pad surface and increase the brake faces (the leading edges of the grooves) so in theory the more grooves the more faces.

2. grooved discs can be used with any pad material as the disc is more durable than a drilled version.

3. discs life is longer than a drilled equivalent.

Disadvantages.

Disc is heavier than a drilled equivalent.

Drilled discs.

1. Lighter weight than a grooved equivalent

2. Good brake bite due to:

A forcing pad material into the holes

B increased braking surface (many leading edges in theory)

3. allowing gases formed during the braking cycle to escape from the disc braking face.

Disadvantages.

Discs can be prone to cracking unless care taken when bedding in

The use of hard race pads(high friction level) can cause cracking giving the disc a limited life.

You will find today that most forms of car motor sport will use grooved discs.