Looks like Mercedes Benz, BMW, Porsche, Lambo, Ferrari and even Nissan ( GT-R ) doesn't know what they are doing...all them holes in those disc brakes are making them brake less.

A solid disc will be better at cold stopping power and maybe even warm stopping power, but when they get hot a cross drilled rotor ( along with a proper vain setup ) will aid in cooling down that rotor and eliminating any gasses.

F1 cars don't have them, but they use extreme duty pads that operate well ONLY at extreme temps so they need the heat.

 

I have those currently and while they stop GREAT when cold and warm, they SUCK HORRENDOUSLY when hot. It's litterally like loosing your brakes.

Now I'm upgrading to 05+ brakes and will try out the 05+ pad to see how it goes.

 

I knew someone would bring this up. The crossdrilled holes in those brakes are NOT for cooling purposes. They are for weight reduction as well as outgassing. Those cars use massive heavy rotors ad can afford to reduce mass with crossdrilling the rotor. The braking dynamics between a 14" heavy x-drilled rotor is NOT the same as a Honda Civic with 10" crossdrilled aftermarket rotors. They are not even manufactured the same for the most part.

Secondly, most of the exotic type race cars with these crossdrilled rotors use a semi-race type pad which outgases during braking. Modern street cars pads do not outgas. That is the reason for the holes. The pads would produce gases as a byproduct and escape through the holes. So like i said, comparing exotic race-type car brakes to a modern passenger car brake system is apples to oranges.

Thirdly, airflow flows perpendicular to the crossdrilled holes, so they offer no advantage to cooling. The main cooling feature of the rotor is the center vanes. The air is drawn in through the center of the rotor hub and through centrifigal motor is "flung" outwards through the center vanes. This, along with airflow on the outside of the rotor creates a dead zone which very little air actually moves.

Typically, the more massive a rotor, the more heat it can absorb, but there are trade-offs in performance. Needless to say comparing those exotic tyoe of brake setups to slapping a $150 set of X-drilled rotors on a passenger car is NOT the same thing at all.

And then before we get the "well, i put a set on my car and it stopped better" statement from someone, i'll just say this. Typically any set of rotors or pads bought will give you better stopping power initially. You could out $50 pep boys specials on there and the brakes will feel better initially. The question is for how long. So the arguement that "well i put some on when i took off my worn used stock brakes and the braking was better" doesn't carry a whole lot of scientific merit. I have friends who autoX and road race who claim most of the OEM brakes are more than up to the challenge of most types of racing punishment with nothing more than a pad change and regular fluid flush.

 

WHS and to add:

1) Mercedes etc.. also accounts for the mass reduction during their design. Vs drilling a bunch of holes into a rotor originally designed to be solid.
2) These makers CAST the holes in, not drill them in. There is a big difference.

 

Thanks for letting me know that. I would like to start doing more AutoX and maybe even a road course every once in a while, so no brakes when hot isn't really an option.

 

+1 No kidding. I threw up in my mouth.

 

Heavy large wheels can overpower the oem brake setup, you may have to go with a larger BBK or very aggressive pads just to get back to oem stopping power.

 

Even a MB C230 Sport will have cross drilled rotors. You are correct about the gasses ( which I also mentioned ) but the holes also allow air to go through them via the scavenging that is happening in the vains of the rotors ( it doesn't feed JUST from the hub ).

As for the holes being for weight reduction, I've never heard of that and the reality is that those holes would likely only lighten the disc by an ounce, which is nothing on a huge heavy as hell disc. Even carbon ceramic discs have tiny holes and they weight next to nothing...those holes would redice the weight my half and ounce at most.

Funny thing is when you talk about the holes being there to reduce mass, then why don't F1 cars use them? They would likely benefit the most don't you think? They use pads that are useless when cold and stop their best when super hot...thus no holes are needed for cooling...yet they don't care to lighten the rotor?

I agree solid discs will be best for 99% of the people here, but I personally am going to get crossdrilled rotores just because they look cool...not because I expect them to brake any better.

 

 

whos rims are hideous i know you are not talking about mines post yours

 

hey ttrank whats the most aggressive pads you think would be the best whats bbk big brake kit? if so thats to much money 4 me the best i could do is go with top of the line pads i know the oems really grab but people told me ceramic are better not sure if i think so

 

^That really depends alot on what you consider "better"

 

Please don't kid yourself or get me started. Your rims are just fugly, but that's my opinion. If you like them more power to you. If you think I'm nuts, ask the other members here for their opinion.

BTW I have the coupe Rays 19s. Sweet rims on a sedan, you should get some.

 

I'd take the Rays anyday.

KTHXBAI

 

Blue Dream - You're not nuts...you have taste.