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By 55Birdman - 17 Years Ago
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In lieu of installing a proportioning valve would it not be just as good to install larger rear wheel cylinders when installing front disc brakes on a bird?
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By charliemccraney - 17 Years Ago
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The proportioning valve controls the rate of the pressure increase to the rear wheels. Simply changing the wheel cylinder will not change the rate. It will change the pressure that acts on the brake shoe. Assuming that the master cylinder piston stays the same diameter, a larger diameter wheel cylinder will provide more pressure while a smaller diameter wheel cylinder will provide less.
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By Pete 55Tbird - 17 Years Ago
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Hello; About a proportioning valve vs different wheel cylinders. If you install disk brakes from a kit from one of the suppliers you may find you do not need a valve. If you do then an adjustable valve will give you controll with a simple twist of the knob vs changing the rear wheel cylinders. I guess what I am trying to say is wait until you have a problem before you try to fix it and then go for simple and easy. The cost of an adjustable valve will be about the cost of two wheel cylinders. Pete
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By John F - 17 Years Ago
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A disk drum combo uses a proportioning valve to keep the rear brakes from locking up before the front does. If you do not have this problem I would say you don't need the valve, if you are having this problem the cheapest way to fix it is with a proportioning valve. Summit has the adjustable ones and they are cheaper than experminting with different wheel cylinders.
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By Canadian Hot Rodder - 17 Years Ago
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I added an adjustable proportioning valve when I converted to Granada front brakes. I know that the "Drop & Stop kits do not use one. When I set mine up, I found the mid point of the valve and set it there for a starting point. After some hard stops in a LARGE empty parking lot, I didn't have to adjust the valve. Car stopped on a dime, nice and straight and only locked up the rears when I hammered the brake peddal.  Rob
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By charliemccraney - 17 Years Ago
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As I understand the function of a proportioning valve, it is designed to prevent the rear wheels fom locking up during a panic stop. With this understanding, if you can slam on your brakes, simulating a panic stop, and your rear wheels lock up, the proportioning valve is either not functioning properly or not adjusted properly. It limits the amount of pressure to the rear wheels so that they don't lock up when much of the weight has been transfered to the front. With casual driving it doesn't really do much of anything.
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By Canadian Hot Rodder - 17 Years Ago
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You may be right Charlie, I am not sure. But when I mean "hammer" on the brakes, I mean"HAMMER"! I brought the car up to about 60 MPH and hit the breaks what I called hard. The car nosed dived and came to a complete stop in a very short distance without skidding and in a straight line. To get the rears to lock, I had to hit the break pedal with both feet as hard as I can and all four wheels locked with the car again skidding in a straight line. I figured that this was pretty good for manual breaks. It sure as heck beat the four wheel drums that seamed to never stop and always would start to pull to one side after a couple of hard breaking sesions. Rob
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By paul2748 - 17 Years Ago
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The TBird parts suppliers have a front disc brake kit that has larger rear cylinders as part of the kit.
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