Those Brembos, fixed caliper? Or not? [Patent inside!]

[ichitaka05]

Originally Posted by Type[R]+

And yet they use cross drilled rotors on the best braking car in the world..... and other high performance cars. They must not be that bad.....

Which are Lexus & Porsche?

Seriously, Lion have good point. I'm no expert in brakes, so just looked around (Super GT, NASCAR & F1 plus others) they did use blank. Few other racing did have slotted rotors (few lower rally, GT300).

[Type[R]+]

Originally Posted by ichitaka05

Which are Lexus & Porsche?

Seriously, Lion have good point. I'm no expert in brakes, so just looked around (Super GT, NASCAR & F1 plus others) they did use blank. Few other racing did have slotted rotors (few lower rally, GT300).

I would say just about all race cars that use metallic brakes use slotted, no disputing that. I'd buy slotted myself if I was into that thing.

Just saying drilled (~cast holes) aren't evil like everyone here seems to think.... Yes, cheap ass ones are, but properly engineered ones have their place.

[Type[R]+]

Originally Posted by LionZoo

The best braking cars in the world are Formula One cars, which all use blank rotors.

OK smart arse. Yes, carbon ones made by Brembo. I think they just might know a bit more about brakes than you.....

[Snaps]

I always thought the drilling wasn't for heat dissipation but was for getting rid of the slight amount of gases that build up when you apply the brakes. Getting rid of this can help with brake pedal feel, especially on the initial push on the brakes.

Slotted, however, is slightly helpful to cooling, but also used mainly to remove the gases, along with things like water and dirt from the brake pad.

This doesn't really apply to Carbon Ceramic pads because they pretty much don't fade... And I would guess the pads used don't produce as many gases, and also that they are kept hot enough (as the are used mainly for racing) to evaporate any water quickly.

As everyone else has said forcing the air to make a 90 degree turn to exit the rotor is NOT an efficient way to get rid of hot air,. Also, if this was the main reason, all of the slots would be in (radially) the same place on the rotor IMO.

[Dave-ROR]

Originally Posted by Type[R]+

Don't have to worry about that at all.....

My stock brakes on the F (360mm x 30mm F / 345mm x 28mm R) :


I guess Brembo and Lexus got it wrong, huh.......

Not at all. Buyers of expensive cars are demanding and demand that they have good looking brakes. Not everything that looks good/cool/high performance actually is though.

Take 911s, they come with cast with holes rotors. Guess what factory 911 race cars have? You get a point if you answer "blanks".

The original question was "why aren't they using slotted or drilled rotors". The answer is simple, because they were racing. No one uses drilled rotors for racing applications and only a minority (including some NASCAR) use slotted. The vast majority use blanks, for good reason.

No one every said that Brembo is full of idiots or that they can't design a proper brake system but you need to understand that the design requirements for a flappy paddle sedan to roam the streets are quite different than that of an endurance race car.

[Dave-ROR]

Originally Posted by MatadorRacing_F1

There is a lot more science to braking than what we are glossing over here and I'm sure you know this. However, I just felt I needed to mention that you failed to highlight in your quotes that they did in fact mention that there are benefits to grooved and slotted rotors. Just trying to be objective here.

I addressed slotted rotors somewhat. Frankly, I'm not specifically against slotted rotors and said that they have their place. You gain some particulate removal with them for sure.

However, for a race car like this FT (or any OEM-type equiv brake restriction race class that doesn't have the insanely expensive NASCAR stuff :P) blanks are still ideal, especially for endurance racing.

As a personal experience, last Sept we ran an 11.5 hour race at Sebring. We had two sets of identical stoptech pads, one set of hawk blues, 1 set of blanks (on the car) and 1 set of slotted rotors that we got for free. Now before we left for the race we THOUGHT (but were too lazy to verify) that we had another set of blanks, as we'd been avoiding using the slotted rotors on purpose).

So after 7.5 hours the first set of pads were done and went metal to metal, requiring the replacement of the rotors as well. So we looked for our second set of blanks only to realize we didn't have any. We put the slotted on and the other new set of stoptechs. 2 hours later, metal to metal again.

That took us out of the race, we were P3 or P4 during that first brake change but having to change them again destroyed any chance of winning or even a podium finish.

For that reason I still don't suggest slotted rotors on race cars. For general DE cars, sure, they crack but not much worse than blanks and not nearly as bad as swiss cheese rotors.

[Dave-ROR]

Originally Posted by NESW20

what makes you more of an expert than anyone else in here? please enlighten us all with your wisdom...

What I'd like to see him provide are FACTS that drilled/cast hole rotors are better than blanks for racing. After all, that's what started this conversation, not what looks cool on a street car.

[Marrk]

There was a time when people advocated for drilled rotors as a weight-saving technique — to scavenge a little unsprung weight. But whatever the race guys are doing is pretty persuasive.

Still, I don't know why they would add those funny pneumatic "jacks" to the Gazoo car, instead of using a floor jack in the pits for tire changes. [Scratches head.]

[Dave-ROR]

Originally Posted by LionZoo

I can expound on why cross-drilled rotors are not a useful design element, but to do a good job would require a lengthy post. The cliff notes version is that rotors are cooled by drawing air in from the hat of the rotor and expelling them out of their major diameter; the outside of the rotor. The centrifugal force of the spinning rotor drives this air movement, resulting in air that wants to move towards the outside of the rotor. What the air (and by extension, all fluids) does not want to do is make a hard 90 degree turn and exit on the rotor face.

More important than the hydrodynamics portion (after all, really the holes were initially there to remove the gas barrier between the pad and the rotors and were never really designed to improve cooling, higher brake temps were a trade off to removing the gas barrier that was causing significant fade with abestos based pads - the rest of your point was spot on of course) is the loss of mass to disperse heat from the pads and caliper. That is what increases brake temps in the caliper and fluid, which is obviously a bad thing.. I mean unless you like melting and bending brake pistons, boiling fluid, etc....

[Dave-ROR]

Originally Posted by Type[R]+

And yet they use cross drilled rotors on the best braking car in the world..... and other high performance cars. They must not be that bad.....

Yet when those cars become race cars they have.. blanks. Odd wouldn't you say?

[Dave-ROR]

Originally Posted by Marrk

There was a time when people advocated for drilled rotors as a weight-saving technique — to scavenge a little unsprung weight. But whatever the race guys are doing is pretty persuasive.

Still, I don't know why they would add those funny pneumatic "jacks" to the Gazoo car, instead of using a floor jack in the pits for tire changes. [Scratches head.]

The weight savings are .1-.2kg generally. It's fairly close to the hub too (although that obviously depends on the size of the rotors). Wheels and tires make a lot more difference there. The negatives far outweigh that positive IMO.

Air jacks are awesome. The car is in the air (all four corners) in seconds, just plug in an air line, no need to carry a jack around, etc.

Video of them working:

Edit: sorry for whoring the thread with replies, I should have multi quoted but didn't realize I'd have that many posts to reply to.

[WolfpackS2k]

^It's good to see someone posting facts. The amount of disinformation on this forum can be quite aggravating some times

[LionZoo]

Originally Posted by Dave-ROR

More important than the hydrodynamics portion (after all, really the holes were initially there to remove the gas barrier between the pad and the rotors and were never really designed to improve cooling, higher brake temps were a trade off to removing the gas barrier that was causing significant fade with abestos based pads - the rest of your point was spot on of course) is the loss of mass to disperse heat from the pads and caliper. That is what increases brake temps in the caliper and fluid, which is obviously a bad thing.. I mean unless you like melting and bending brake pistons, boiling fluid, etc....

I agree. It's kind of a funny trade-off isn't it? We try to make our rotors as light as possible for unsprung reasons, but their purpose as a heat sink actually cries out for as much mass as you can give them. I guess I highlighted the flow element of the rotors because I did a lot of forced flow cooling design when I was an engineer, so that was what I was thinking of when I posted.

I'd also point out that having holes in your rotor, no matter how they're made and what after process treatment you use, will increase the stresses that the rotor sees. It's unavoidable; a hole is a stress concentration. Granular alignment of the metal might help alleviate it some, but in the end the shape of the hole is just not good for stresses.

[Matador]

Originally Posted by LionZoo

The best braking cars in the world are Formula One cars, which all use blank rotors.

Formula one cars do not use the typical braking system.

Originally Posted by LionZoo

I can expound on why cross-drilled rotors are not a useful design element, but to do a good job would require a lengthy post. The cliff notes version is that rotors are cooled by drawing air in from the hat of the rotor and expelling them out of their major diameter; the outside of the rotor. The centrifugal force of the spinning rotor drives this air movement, resulting in air that wants to move towards the outside of the rotor. What the air (and by extension, all fluids) does not want to do is make a hard 90 degree turn and exit on the rotor face.

Cross drilled rotors are prone to cracking. The massive and frequent braking stresses that race cars go through coupled with far more advanced suspension and far lighter wheels make cross drilled rotors pretty much useless on a race car.

Originally Posted by Dave-ROR

I addressed slotted rotors somewhat. Frankly, I'm not specifically against slotted rotors and said that they have their place. You gain some particulate removal with them for sure.

However, for a race car like this FT (or any OEM-type equiv brake restriction race class that doesn't have the insanely expensive NASCAR stuff :P) blanks are still ideal, especially for endurance racing.

I'm not disagreeing with you. But depending on how thick and wide rotors are, cross drilling really makes a difference in the weight. Sure it comes down to an aesthetic choice for most people but it does save on unsprung weight. Not that I recommend them either, but I do think the whole "throw them under the bus, they are useless" attitude is a bit extreme.

Originally Posted by Marrk

There was a time when people advocated for drilled rotors as a weight-saving technique — to scavenge a little unsprung weight. But whatever the race guys are doing is pretty persuasive.

See above.