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Tilikum Turbo's Avatar
 
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Anyone install a brake-bias adjustment in their car?

I'd like at times to be able to adjust the brake-bias on my car.

Anyone install such a system in their 911/930?
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Old 04-17-2014, 08:28 PM
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What are you trying to accomplish?

I installed one in my race car a few ago, then removed it. I switched to a dual master cylinder system.
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Old 04-17-2014, 08:42 PM
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I have the dual master cylinders with the remote brake bias knob in the cockpit. Find it handy in some instances, but it isn't uses offend after it's set.
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Old 04-17-2014, 10:29 PM
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Can you accomplish the same with a proportioning valve?
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Old 04-18-2014, 12:39 AM
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Sorta, just limited to the amount of adjustment.
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87 911 Carrera platform
Twin Garrett's, Big Valve, Xtreme Cylinder Heads, JB Racing cylinders and machine work, custom JE pistons, GT2 EVO cams, GT3 oil pump, modified 3.2L intake, 80mm TB, custom Intercooler, equal length headers, DFI, KEP Stage 2 custom twin disc, G50 custom gear set, LSD, Tilton trans pump, Fluidyne cooler
Old 04-18-2014, 06:22 AM
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We should clear up the terminology. Brake bias is a knob to adjust the front/rear balance between dual master cylinders. Here's a good description on how a proportion valve works, http://tiltonracing.com/wp-content/uploads/2013/07/98-1261-Brake-Proportioning-Valve.pdf
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Old 04-18-2014, 06:33 AM
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On a single master cylinder car like most street cars have the brake bias valve is an adjustable pressure regulator in the hydraulic line going to the rear calipers.

You don't reduce the pressure going to the front calipers.. you control that with your foot with pedal pressure.

With the brake bias in the rear hydraulic line you can adjust how much hydraulic pressure is going to the rears in relation to whats going to the fronts so they don't lock up before the fronts during hard braking in a straight line and while turning in and trail braking into corners.

If you reduce the pressure going to the rears to give maximum braking distances in a straight line and during turn in and trail braking going into corners in the dry it's going to be too much in the wet and the rears will lock up and you'll spin off the road.
Then you can turn the brake bias knob to reduce hydraulic pressure going to the rear calipers so they don't lock up during weight transfer to the front wheels while braking hard.
Old 04-18-2014, 07:29 AM
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Quote:
Originally Posted by totle View Post
Can you accomplish the same with a proportioning valve?
No. Proportioning valve can only limit the amount of pressure so don't do anything until you hit the trigger pressure, or the "knee" on the graph.

Useful for ensuring the rears don't lock if the rear calipers are too big (stock 3.2), but no use at the front.

Dual masters with a balance bar is the only game. Or just get the brake bias right to start with.
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Old 04-26-2014, 02:49 AM
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