Brake ducts - rotor cooling theories, applications, and pics - Honda-Tech

BrakeExpert · 11-12-2006, 08:25 PM

Some people are misinformed about brake ducts, I will try and clarify.

Brake ducts serve to cool the brakes via convection.

This is an example of a not-so effecient way to do it.

This pictured setup for cooling is alright, but would me much more effective if the cool air was directed into the back of the "dead space" of the rotor, where the vanes begin. You want to feed fresh air into the vanes opposed to on the rotor's surface because the rotor will cool a lot more effectively having cool air rush out through that much larger surface area opposed to one spot.

This is a decent way to do it.

The cooling duct work is alright, but still just merely aimed at the brake. Given the wheel will spin, this air is just going to circulate in the wheelwell. ALSO, based on the stamp on the steering knuckle, thats an EF. And thats also the small brakes, the 9.5" rotors. It would be SO much more effective just to get a brake upgrade, even the 10.3" rotors and bigger pad would offer a larger, thicker heatsink, and wouldn't add the noise and aero-loss of a brake duct. Not to attack your setup, but bigger brakes would be more effective, unless were talking cost, and this took you like no money to make.

Brake ducts are good in general, but some cars may or may not need them. The BETTER option is usually to get a larger brake setup, to go to a larger rotor which is thicker with more vanes. Those rotors hold more heat, and because of the surface area, dissapate it better. If you go to a VERY large brake setup, and it holds so much heat, that on a track the brakes can't cool fast enough that you are fading, then ducting would help. On most Road Hondas, the best thing to consider first is a brake upgrade with a larger rotor. With stock brakes and ABS, unless the brakes are fading on you, brake ducts will only increase wind noise and negatively affect aerodynamics of the car, granted this won't be noticable to most people.

When I say "better" upgrade to get bigger rotors, is that when you run the numbers, with most car and applications, at high speeds, the additional rotational mass just doesn't equal the loss in HP when reducing aero with a brake duct, assuming a slick car front. Again, this is on a racecar, depending on the road car, it may vary on track times, given unspring weight, speed, temp, etc.

Open spoked wheels help. If you have stock steelies with wheel covers, you'd be surprised how putting on a set of aftermarket wheels will help cool the brakes by letting more air flow around the rotor. Some rims are actually angled in the spokes and this can act like rotors with angled vanes by pulling air away from the rotor.

This is a good way to do it, very cost effective, and gets the cool air where you want it, so it can flow out of the surface area of the vanes.

Always make sure to point rotors with angled vanes towards the front, meaning the vanes should not "point" into the wind. The angled vanes don't "bite" into the wind, they actually go the other way to cool more effectively. This is where brake ducts really do a lot more. On cars like the NSX with curved vane rotors, piping a brake duct to the rotor's center flows cool air in, and is spun out by these vanes. On cars with angled vanes, they don't really cool the car down effectively until you are going about 50 to 60 miles per hour.

This picture has done it correctly, air going into the hub, and out the vanes. It also has the slots pointing the right way.

When talking slotted rotors, most people do it wrong. The Corvette Z06 does it correctly, most other cars do it wrong. The slots are suppose to contact the pad at the top, then to the bottom. The downfall of this is the noise. Many with straight vaned rotors and slots put them the other way either for aestetics, or because it helps with bite but doesn't add the noise. Listen to track cars. Many of them with brake ducts have angled vents in the rotors, some with slots in them, and metal pads. They stop very well, but the brakes can get very loud, which most dont want on a road car, and is usually overkill.

Please post any pics ya got!!

I hope some of this has been informative, I'm not making any assumptions here, I'm talking theory, and I have no numbers here.

I stole all these pics, none of em are mine.

Modified by Redline57 at 12:07 PM 2/7/2007

Flashmn · 11-13-2006, 03:10 AM

Also alot of track cars have brakes that arent directly comparable to street cars, nor should they, track cars have a very different work-orientation to street cars. Track car brakes seldomly really cool down, they have to work at high temps. Whilst streetcars need that cold stopping power.

743power · 11-13-2006, 09:31 AM

it's usually not an option to upgrade to larger rotors in many road racing classes, like IT.

BrakeExpert · 12-10-2006, 09:49 PM

Really? I didn't know about "classes" I thought road racing meant....road...racing. Well Aside from special classes, I was talking about just getting more out of your brakes, more effeciency, like getting more stop from the rotor.

Muckman · 12-11-2006, 10:16 PM

Its kinda hard to route the air duct the "correct" way on a FWD car when there is a big AXLE in the center of the hub.

blinx9900 · 12-11-2006, 11:14 PM

excellent wright up! ive been toying with this idea for awhile, this really helped me thanks!

BrakeExpert · 12-11-2006, 11:16 PM

Well yes it is, thats why I posted that 3rd picture. I have seen several people use the dust shield as a reference and mount of how to get air into those heat vanes. It can be tricky, but I still feel thats one of the best ways to do it.

blinx9900 · 12-11-2006, 11:48 PM

redline, are you saying that if a car is going this way ---> the slots on a slotted rotor should be like this / and NOT like this \ cause i was going to do mine like this \ but i noticed all the super GT cars are like this /

BrakeExpert · 12-12-2006, 01:08 AM

Yes I am. The top of the slot contacts the pad first. Most cars have it wrong because of a factor called noise. Even some high end cars come with slots cause people want them, but they don't want the noise. Ever notice how track cars have all metal pads? Those are noisy as hell on the road, so they use ceramic metallic compounds.

blinx9900 · 12-12-2006, 07:51 PM

i understand thanks, how much performance are you really hurting by putting them on like this \ are you reducing actual braking, cooling, or the resurfacing of the pad by the slots?

BrakeExpert · 12-12-2006, 08:10 PM

You aren't hurting performance much on a road car by doing this. I reccomend blank rotors for any application, because I find slots to be nothing more than a reduction of surface area. You would be reducing cooling a slight bit though, assuming you had no ducting and open spoked wheels. I wouldn't imagine this affects 60-0 distances because the surface area is the same, but I guess based on the pad shape, rotor size, etc. I don't know, it may be on a specific basis. I have no numbers to prove how it affect it specifically, I just know that on REAL race cars, any slotted rotors have the slot contact the pad at the outer rim first..... like /.

blinx9900 · 12-12-2006, 08:16 PM

then you pobably would think my custom 18 slot rotors are worthelss haha, its cool though we all have our own theory, mine is that its ok to reduce surface area so long as you increase the brake pads co efficient of friction (rougher pad) kinda like full face clutch vs 6 puck concept....

BrakeExpert · 12-12-2006, 08:26 PM

Well I mean if you go from say stock 9.5" brakes to a custom 14" rotor kit that has holes and slots and small pads, it will still probably stop better just because the rotor is SO much bigger. Yeah pads make the biggest difference with brakes, its the most cost effective way to get more stopping power, to switch to a better pad compound.

blinx9900 · 12-12-2006, 08:34 PM

agreed, cobalt GT sport for me

so far so good, havent really raped'em yet though... i'll see how they hold up under boost...

slow-as-heck · 12-13-2006, 06:47 AM

i am confused as to how you could do this "properly" with the large axel of a fwd car going into the hub.

any ideas?

BrakeExpert · 12-13-2006, 10:06 AM

Again, see the 3rd picture, thats about the best way to do it, a custom bracket where the dust shield goes.

blinx9900 · 12-13-2006, 11:21 AM

it might just be me but even after looking at the third pic (2nd one wont load) i still dont understand how that could be done on a front drive car, i can see pic 1 working pretty good though...

BrakeExpert · 12-13-2006, 01:10 PM

What's confusing to understand? You see the 3rd pic right? The dust shield is removed and there is that hose going to right behind the hub. Granted that picture may or may not be a Honda, if it was, that'd be the backside of the axle, since our cars have the steering rack behind the axle. Route the hose for air from the front of the car for the intake, and use some zip ties, clamps, etc to get it to the back side of the hub, so that when the rotor is on, the air is going to the vanes of the rotor. Yes coming from that connection, the hose may have to run up to the knuckle, and then to the body of the car, but in this pic, the hose does not go through where an axle would go, as that is clearly a front wheel drive car's front knuckle, and there must be an axle in there.

mikestypes · 12-13-2006, 02:58 PM

Quote:

Originally Posted by Redline57

When talking slotted rotors, most people do it wrong. The Corvette Z06 does it correctly, most other cars do it wrong.

It's funny you bring up the Z06 because GM screwed the rotors on that car bad. Ever notice how both front rotors are actually left side castings and that on the passenger side, the vanes curve the wrong way!

BrakeExpert · 12-13-2006, 03:21 PM

Really? Cause I'll be honest, I never actually checked that car out in particular. I was talking to a salesman over at the Ferrari dealer, and we were talking brakes. And we looked at the Aston Vanquish and some had the rotors vented wrong and he said they did that for the customers. I have seen pics of the Z06, but never actually seen one, and it was that salesman that told me they did it right. Maybe they did expletive up on em, I mean it is GM, and their quality is....well you know.

mikestypes · 12-13-2006, 10:13 PM

http://forums.corvetteforum.co...d=100

It was actually the C6 Z51 and the Z06.....

BrakeExpert · 12-19-2006, 07:16 PM

To update, I have researched and talked to people, and YES, Chevrolet did expletive up regarding their new Z06 and I was told it has two front left rotors. Off the record, someone did an independant test and found the "incorrectly" mounted rotor had the same, if not cooler, temperature from the correctly mounted one, but I have almost no more info on this, so can't give any verification to this. But apparantly the Corvette is upto 'General Motors quality' and we all know how top of the line their build is.....

mrlegoman · 01-01-2007, 08:26 PM

Nice post. One of the pics did not come up, is it possible to fix it?

blinx9900 · 01-01-2007, 08:45 PM

Quote:

Originally Posted by mrlegoman

Nice post. One of the pics did not come up, is it possible to fix it?

x2

BrakeExpert · 01-01-2007, 09:10 PM

Those pics weren't mine, sorry. The second picture was pretty much some home depot ducting for a dryer and a rectangular bracket pointing the air toward the backside of the rotor with no dust shield in place.
Honestly your most cost effective way to do it is get some hose and if your real lazy, cut the dust shield and get the air to aim as close to the center as possible so that it aims at the inside of the rotor's hat, thats the idea here.

11-12-2006, 08:25 PM	#1
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Brake ducts - rotor cooling theories, applications, and pics Some people are misinformed about brake ducts, I will try and clarify. Brake ducts serve to cool the brakes via convection. This is an example of a not-so effecient way to do it. This pictured setup for cooling is alright, but would me much more effective if the cool air was directed into the back of the "dead space" of the rotor, where the vanes begin. You want to feed fresh air into the vanes opposed to on the rotor's surface because the rotor will cool a lot more effectively having cool air rush out through that much larger surface area opposed to one spot. This is a decent way to do it. The cooling duct work is alright, but still just merely aimed at the brake. Given the wheel will spin, this air is just going to circulate in the wheelwell. ALSO, based on the stamp on the steering knuckle, thats an EF. And thats also the small brakes, the 9.5" rotors. It would be SO much more effective just to get a brake upgrade, even the 10.3" rotors and bigger pad would offer a larger, thicker heatsink, and wouldn't add the noise and aero-loss of a brake duct. Not to attack your setup, but bigger brakes would be more effective, unless were talking cost, and this took you like no money to make. Brake ducts are good in general, but some cars may or may not need them. The BETTER option is usually to get a larger brake setup, to go to a larger rotor which is thicker with more vanes. Those rotors hold more heat, and because of the surface area, dissapate it better. If you go to a VERY large brake setup, and it holds so much heat, that on a track the brakes can't cool fast enough that you are fading, then ducting would help. On most Road Hondas, the best thing to consider first is a brake upgrade with a larger rotor. With stock brakes and ABS, unless the brakes are fading on you, brake ducts will only increase wind noise and negatively affect aerodynamics of the car, granted this won't be noticable to most people. When I say "better" upgrade to get bigger rotors, is that when you run the numbers, with most car and applications, at high speeds, the additional rotational mass just doesn't equal the loss in HP when reducing aero with a brake duct, assuming a slick car front. Again, this is on a racecar, depending on the road car, it may vary on track times, given unspring weight, speed, temp, etc. Open spoked wheels help. If you have stock steelies with wheel covers, you'd be surprised how putting on a set of aftermarket wheels will help cool the brakes by letting more air flow around the rotor. Some rims are actually angled in the spokes and this can act like rotors with angled vanes by pulling air away from the rotor. This is a good way to do it, very cost effective, and gets the cool air where you want it, so it can flow out of the surface area of the vanes. Always make sure to point rotors with angled vanes towards the front, meaning the vanes should not "point" into the wind. The angled vanes don't "bite" into the wind, they actually go the other way to cool more effectively. This is where brake ducts really do a lot more. On cars like the NSX with curved vane rotors, piping a brake duct to the rotor's center flows cool air in, and is spun out by these vanes. On cars with angled vanes, they don't really cool the car down effectively until you are going about 50 to 60 miles per hour. This picture has done it correctly, air going into the hub, and out the vanes. It also has the slots pointing the right way. When talking slotted rotors, most people do it wrong. The Corvette Z06 does it correctly, most other cars do it wrong. The slots are suppose to contact the pad at the top, then to the bottom. The downfall of this is the noise. Many with straight vaned rotors and slots put them the other way either for aestetics, or because it helps with bite but doesn't add the noise. Listen to track cars. Many of them with brake ducts have angled vents in the rotors, some with slots in them, and metal pads. They stop very well, but the brakes can get very loud, which most dont want on a road car, and is usually overkill. Please post any pics ya got!! I hope some of this has been informative, I'm not making any assumptions here, I'm talking theory, and I have no numbers here. I stole all these pics, none of em are mine. Modified by Redline57 at 12:07 PM 2/7/2007

11-13-2006, 03:10 AM	#2
Flashmn Senior Member Join Date: Feb 2005 Location: Heinola, Finland Posts: 1,199	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) Also alot of track cars have brakes that arent directly comparable to street cars, nor should they, track cars have a very different work-orientation to street cars. Track car brakes seldomly really cool down, they have to work at high temps. Whilst streetcars need that cold stopping power. __________________ 1987 Toyota Hilux Xtra-cab 2.4 Diesel 1990 Toyota Corolla turbocharged 1.6

11-13-2006, 09:31 AM	#3
743power Without Honda, there is no Super Aguri Join Date: Feb 2002 Location: at the track Posts: 5,955	Re: Brake ducts - rotor cooling theories, applications, and pics (Flashmn) it's usually not an option to upgrade to larger rotors in many road racing classes, like IT. __________________ "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction." -Albert Einstein

12-10-2006, 09:49 PM	#4
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (743power) Really? I didn't know about "classes" I thought road racing meant....road...racing. Well Aside from special classes, I was talking about just getting more out of your brakes, more effeciency, like getting more stop from the rotor.

12-11-2006, 10:16 PM	#5
Muckman Senior Member Join Date: Sep 2001 Location: Rochester, NY Posts: 7,056	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) Its kinda hard to route the air duct the "correct" way on a FWD car when there is a big AXLE in the center of the hub. __________________ 426whp/300ft-lbs at 17psi

12-11-2006, 11:14 PM	#6
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) excellent wright up! ive been toying with this idea for awhile, this really helped me thanks! __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-11-2006, 11:16 PM	#7
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (Muckman) Well yes it is, thats why I posted that 3rd picture. I have seen several people use the dust shield as a reference and mount of how to get air into those heat vanes. It can be tricky, but I still feel thats one of the best ways to do it.

12-11-2006, 11:48 PM	#8
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) redline, are you saying that if a car is going this way ---> the slots on a slotted rotor should be like this / and NOT like this \ cause i was going to do mine like this \ but i noticed all the super GT cars are like this / __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-12-2006, 01:08 AM	#9
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) Yes I am. The top of the slot contacts the pad first. Most cars have it wrong because of a factor called noise. Even some high end cars come with slots cause people want them, but they don't want the noise. Ever notice how track cars have all metal pads? Those are noisy as hell on the road, so they use ceramic metallic compounds.

12-12-2006, 07:51 PM	#10
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) i understand thanks, how much performance are you really hurting by putting them on like this \ are you reducing actual braking, cooling, or the resurfacing of the pad by the slots? __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-12-2006, 08:10 PM	#11
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) You aren't hurting performance much on a road car by doing this. I reccomend blank rotors for any application, because I find slots to be nothing more than a reduction of surface area. You would be reducing cooling a slight bit though, assuming you had no ducting and open spoked wheels. I wouldn't imagine this affects 60-0 distances because the surface area is the same, but I guess based on the pad shape, rotor size, etc. I don't know, it may be on a specific basis. I have no numbers to prove how it affect it specifically, I just know that on REAL race cars, any slotted rotors have the slot contact the pad at the outer rim first..... like /.

12-12-2006, 08:16 PM	#12
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) then you pobably would think my custom 18 slot rotors are worthelss haha, its cool though we all have our own theory, mine is that its ok to reduce surface area so long as you increase the brake pads co efficient of friction (rougher pad) kinda like full face clutch vs 6 puck concept.... __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-12-2006, 08:26 PM	#13
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) Well I mean if you go from say stock 9.5" brakes to a custom 14" rotor kit that has holes and slots and small pads, it will still probably stop better just because the rotor is SO much bigger. Yeah pads make the biggest difference with brakes, its the most cost effective way to get more stopping power, to switch to a better pad compound.

12-12-2006, 08:34 PM	#14
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) agreed, cobalt GT sport for me so far so good, havent really raped'em yet though... i'll see how they hold up under boost... __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-13-2006, 06:47 AM	#15
slow-as-heck Join Date: May 2005 Posts: 303	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) i am confused as to how you could do this "properly" with the large axel of a fwd car going into the hub. any ideas? __________________ Buy my car -> 2000 Civic Hatch with B18C1, 5-lug, etc http://honda-tech.com/zerothread?id=2270018

12-13-2006, 10:06 AM	#16
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (slow-as-heck) Again, see the 3rd picture, thats about the best way to do it, a custom bracket where the dust shield goes.

12-13-2006, 11:21 AM	#17
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) it might just be me but even after looking at the third pic (2nd one wont load) i still dont understand how that could be done on a front drive car, i can see pic 1 working pretty good though... __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-13-2006, 01:10 PM	#18
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) What's confusing to understand? You see the 3rd pic right? The dust shield is removed and there is that hose going to right behind the hub. Granted that picture may or may not be a Honda, if it was, that'd be the backside of the axle, since our cars have the steering rack behind the axle. Route the hose for air from the front of the car for the intake, and use some zip ties, clamps, etc to get it to the back side of the hub, so that when the rotor is on, the air is going to the vanes of the rotor. Yes coming from that connection, the hose may have to run up to the knuckle, and then to the body of the car, but in this pic, the hose does not go through where an axle would go, as that is clearly a front wheel drive car's front knuckle, and there must be an axle in there.

12-13-2006, 03:21 PM	#20
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (mikestypes) Really? Cause I'll be honest, I never actually checked that car out in particular. I was talking to a salesman over at the Ferrari dealer, and we were talking brakes. And we looked at the Aston Vanquish and some had the rotors vented wrong and he said they did that for the customers. I have seen pics of the Z06, but never actually seen one, and it was that salesman that told me they did it right. Maybe they did expletive up on em, I mean it is GM, and their quality is....well you know.

12-13-2006, 10:13 PM	#21
mikestypes Join Date: Sep 2002 Location: Calgary, AB, Canada Posts: 206	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) http://forums.corvetteforum.co...d=100 It was actually the C6 Z51 and the Z06.....

12-19-2006, 07:16 PM	#22
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (mikestypes) To update, I have researched and talked to people, and YES, Chevrolet did expletive up regarding their new Z06 and I was told it has two front left rotors. Off the record, someone did an independant test and found the "incorrectly" mounted rotor had the same, if not cooler, temperature from the correctly mounted one, but I have almost no more info on this, so can't give any verification to this. But apparantly the Corvette is upto 'General Motors quality' and we all know how top of the line their build is.....

01-01-2007, 08:26 PM	#23
mrlegoman Senior Member Join Date: May 2001 Location: Lynchvegas, Va, USA Posts: 3,409	Re: Brake ducts - rotor cooling theories, applications, and pics (Redline57) Nice post. One of the pics did not come up, is it possible to fix it? __________________ My Car Car dyno YouTube F/S:EG Wide Body Fenders

01-01-2007, 09:10 PM	#25
BrakeExpert Banned Join Date: Oct 2006 Posts: 1,223	Re: Brake ducts - rotor cooling theories, applications, and pics (blinx9900) Those pics weren't mine, sorry. The second picture was pretty much some home depot ducting for a dryer and a rectangular bracket pointing the air toward the backside of the rotor with no dust shield in place. Honestly your most cost effective way to do it is get some hose and if your real lazy, cut the dust shield and get the air to aim as close to the center as possible so that it aims at the inside of the rotor's hat, thats the idea here.