Rear brake cooling ducts

[Steve W]

I kind of suspected the rear brake ducts from a 2010 GT3 would fit nicely along the trailing arms on the earlier 911s. So under the car tonight I though I'd verify and other than figuring a method of attachment, it's just about a perfect fit. These ducts are very effective at reducing the rear disc temps on the GT3s by 150 deg F at the track. I don't plan to install them, but should be good reference for anyone looking at options:

[midnight911]

sweet...how do we get them? you know, at OUR price points...

don't think there are that many wrecked gt3's...

[175K911]

Awesome Steve! Thanks for mocking it up for us. Almost looks like if there was a mounting plate welded to the control arm, it was made for our cars.

[Steve W]

They're not that bad - last I checked I think they were about $65 each. I'm sure Pelican can get them for you.

p/n L&R: 997.575.531.90 and 997.575.532.90

You had to let my secret out didn't you Just kidding! Good job Steve!

[Steve W]

opps, hehe, at least I havent' told everyone about your monster 996 brakes yet

[Walt Fricke]

Puhn or some one of the engineers who write race car tweaking books said that you really want to direct brake rotor cooling air either into the center so it comes out the internal rotor ducting radially, or you want a "clamshell" duct which blows the cooling air on both sides of the rotor.

Otherwise, the theory goes, you can warp the rotors by having one side a lot cooler than the other.

On a GT3, do these ducts just send the air at the inner face of the rotor (as your mockup and their design would suggest? Obviously, to get cooling air into the central part of trailing arm 911 rears with the parking brake assembly in place would be a challenge. Are the GT3 rears, with their multi-link system, sufficiently different in this regard?

I've no vested interest in theory if it doesn't matter in practice, but this has me wondering.

Walt

[Steve W]

That's theory, for a 911, it's pretty hard to warp the rotors. Rotor and pad life is main benefit along with keeping the brake fluid below boiling. It works for the back of a GT3 exactly as mocked up for a early 911, ducting the air to the back side of the disk, no different than using 993 front brake deflectors on the front A-arms on early 911s, or like 996 and 997 GT3s which have inner control arms deflectors to the inside of the front disks.

[dad911]

Originally Posted by Steve W

.....

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Is that a Carbon Fiber Wheel???

[Flieger]

One of those Dymag Carbon fiber rim/Magnesium Star wheels.

I'm still not finished! Lots of little hicups. And no time. Been super busy with work. I leave for Mexico to do some consulting work so there goes another track day missed. Sooooon!

opps, hehe, at least I havent' told everyone about your monster 996 brakes yet

[rblove]

Has anyone tried to install the rear GT3 brake ducts on a 89 or older 911? Pelican and Suncoast in FL list show the ducts at $260± for a pair. No slight intended but does anyone know a source for a lower price?

[spyerx]

FWIW the 997gt cars have these on the suspension arm and also have a naca style duct on the belly pan that also blows air at the braking components. The front ducts are huge. I have those from the cup car. The gt2rs are the biggest

They do get expensive and have a habit of finding themselves in the runoff areas of tracks :-)

You should try some caliper and brake paint and see how hot they are getting and if cooling is a real problem in the back. On modern cars with stability control systems the rear brakes get worn fast. On my 997rs i ran with all systems off and rear pads last 2x as long as fronts. Rears didn’t really work that hard.

[Bill Verburg]

Originally Posted by spyerx

F......

They do get expensive and have a habit of finding themselves in the runoff areas of tracks :-)

You should try some caliper and brake paint and see how hot they are getting and if cooling is a real problem in the back. On modern cars with stability control systems the rear brakes get worn fast. On my 997rs i ran with all systems off and rear pads last 2x as long as fronts. Rears didn’t really work that hard.

This^

[spyerx]

Brembo / Race Technologies sells these paints in the US. I got this from a friction engineer when I was first trying different pads (I use a compound called RE10 which is an endurance friction compound which likes to be quite warm before it bites well).

The paint you apply to the top edge of the rotor (not not he friction surface) and put 3 stripes one of each color. You want to come in from a run and have the red and orange paints in tact. The Green paint will turn 'silver'.



Brake caliper Paint:
-- Green: 430C/806F
-- Orange: 560C/1040F
-- Red: 610C/1130F

Once they reach the specified temp range, they oxidize which turns them green/red: white or an orange/off-white (yellowish tint). If they reach the peak temperature.

Caliper Temp: 140C/284F - 160C/320F, max 180C/256F
Rotor Temp: 450C/842F - 550C/1022F (in pit lane if measured by IR).
Max: 650C/1202F (measured by rotor paint)

Basically we want to flash the green paint and for the most part be in the orange paint range if applied on the disc. We can turn the red paint to white on the rubbing surface of the disc but not in the disc vane itself.

Summary:
On Vanes - Flash Green and into Orange, no Red
On Suface - Flash Green, Orange, Red is OK