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914World.com _ 914World Garage _ Rear Brake Cooling

Posted by: Eddie914 May 25 2007, 04:59 PM

I'm running 911SC brakes with Porterfield R4 pads and ATE SuperBlue fluid. It is not uncommon for the pedal to get spongy after a bit of spirited driving.

The last time the brakes were bled, bleeding the front brakes did not firm up the brake pedal, but bleeding the REAR brakes returned the nice stiff feel to the pedal. Could the rear brakes be overheating before the front brakes?

Is anyone using any type of brake cooling on their 914?

Where would be a good place to position duct intakes?

TIA

Eddie

Posted by: Eric_Shea May 25 2007, 07:22 PM

I was toying with some ideas after seeing Elliot's oil cooler mod on his rockers. It involves small NACA ducts at the rear of the rockers. Fairly easy to glass in. The question is the mount at the rotor eye...

Could very well be your bias is set wrong (is it adjustable?). If you have a T you might want to go back to the factory P-valve that allows adjustability and a more progressive mix. (donning flame retardant undies)

Posted by: URY914 May 25 2007, 09:24 PM

I always had problems with the stock p-valve when it came to bleeding the rears. I changed the stock to an ajustable lever type by Tilton and the problem was solved. Someone here was just selling the knob type p-valve.

Never had a problem with the rears overheating even when I ran track events.

Posted by: Eddie914 May 25 2007, 09:49 PM

The fronts are cooled by 3" ducts to backing plates that fit tightly inside the rotors with hub block-off plates.

An adjustable proportioning valve is installed in the line at the rear of the tunnel and the stock proportioning valve has been eliminated. The valve was initially set wide open as many suggested. With a 3.2/6, 901 transaxle, 225/50/16 front tires and 245/45/16 rear tires, rear lockup was prevalent. the biasing has been adjusted to the point that the rears did NOT lock up any more, then an extra turn was added for a safety margin.

I suspect more front bias could be added to equalize brake temps but total braking may be compromised. i was hoping to add cooling to the rear to optimize total braking.

Then I will mess up the balance of whole equation by adding the Wilwood Superlite II calipers and the 309mm rotors that are waiting in the garage.

Thanks

Eddie

Posted by: iamchappy May 25 2007, 10:03 PM

I plan on mocking something up using the ducts from the AJ front A Arm ducts.
I dont think they are really needed in the rears for my use, but I am doing it because it's kinda cool.......and I have the stuff laying around to do it.
I have so much stuff to post with the fabrication of my turbo, brakes, ebrakes, interior, stereo and stiffening, and body, I will have to sit down some night and post away....

Posted by: rfuerst911sc May 26 2007, 07:54 AM

Porsche 993's have a front brake " deflector " which basically is a piece of flat plastic that bolts to the A-arm and deflects air into the eye of the rotor. I would think a similiar approach could be made to bolt/zip tie to the rear swing arm to deflect air into the rear rotor. It just has to have the right dimensions to "scoop" the air going under the car up into the rotor area.

Posted by: Eddie914 May 26 2007, 05:13 PM

This is a nice setup ...

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Posted by: Eddie914 May 26 2007, 05:15 PM

The car that it is installed on isn't too bad of a mid engined car either...

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Posted by: Eddie914 May 26 2007, 09:40 PM

has anybody tried anything like this?

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Posted by: Eddie914 May 26 2007, 09:40 PM

Bottom ...

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TIA

Eddie