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Old 05-31-2004, 07:18 PM
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Proportioning Valve Adjustment

I just put disk brakes on the front of my 37 Ford, with drums on the back. I installed the prop. valve in the rear brake line.

How should I adjust it, and test it?

Thanks

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Old 05-31-2004, 07:29 PM
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Is it an adjustable proportioning valve?

If not, you can't adjust it.
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Old 05-31-2004, 07:36 PM
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Yes, it is adjustable. I believe you turn it clockwise to increase the pressure.
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Old 05-31-2004, 07:38 PM
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Trial and error then..................................
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Old 06-03-2004, 06:52 PM
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Turning clockwise reduces pressure/restricts flow. Turn it ccw from full cw, drive it down the street about 30 mph and do a panic stop. If the fronts lock first, take another turn cw, it the rear locks first ccw for a 1/4 turn. Repeat until al 4 lock together. It has never taken me more than three tries to get it balanced out.

Trees
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Old 06-03-2004, 08:23 PM
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Thanks Trees. What ever happened to the trip you were planning to Nashville?
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Old 06-05-2004, 06:21 PM
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It fizzled out from lack of interest, I guess. I was ready to go!!

Trees
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Old 06-09-2004, 09:41 AM
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Your better off dialing in a little more front brake than rear. The pavement you are testing on will not be the same as the pavement you are sliding on when someone pulls out in front of you. Locking the front wheels first is the easiest and faster to correct rather then letting a rain slick road cause you to lose the rear end which probably result in a crash into a ditch rather maintaining control of yaw while there is no traction at the rear.
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Old 06-11-2004, 06:47 AM
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JG, agree 100 % on your descriptions of handling aspects. In theory, brakes set up under one set of braking surface conditions should stay the same under all other conditions. Theory has to do with coefficient of friction and most theories are developed with asumptions. In the case of brakes, it is assumed the front and rear wheels experience the same conditions simultaneously (coefficient of friction is the same) and distribution of weight remains constant. I know of racers that have a proportioning valve in the cage with them to make some fine tweeks as fuel burns out. Also have heard of hair raising moments from tweaking the wrong way. Winner's burnouts can be impressive though.

Trees
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Old 06-11-2004, 08:37 AM
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No offense Trees but I always bias the front a little more than the rear. There is a difference front end loading between a 30mph panic stop and a 60mph panic stop. In the latter, the car noses over more and the rears are unloaded a little more. If you have ever gone endo when the rear wheels lock up before the front, you will heartily agree with me!!
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Old 06-11-2004, 08:56 PM
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Willys, you are correct as usual. Note that I said "assumed" the loading stays the same in theory. Yes, Ive been there done that with rear ends locking up first. My pickup was really bad until I installed the adjustable proportioning valve. Try a front wheel drive vehicle on ice with rear disc brakes. The rear is skating and you have not even applied enough brake pressure to overcome the tranny turning the front wheels!! It is a totally unnatural act to push the tranny into neutral when applying the brakes!!! My wife is on her 4th one of these hummers and will not even attempt to drive if there is a possibility of ice or snow.

Trees
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Old 06-16-2004, 10:41 AM
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Trees, Your setting procedure sounds simple enough. One question however, Where is the best starting point on the prop valve? My valve is capable of 8 full rotations. I would assume the place to begin is 4 full turns starting from closed. Does this sound right?
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Old 06-16-2004, 06:36 PM
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Thanks to all for the help on adjusting the valve. I had to turn it 8 turns to get the best braking for now. I still need to do some fine tuning for different conditions.
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Old 06-16-2004, 08:26 PM
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Mid point is as good as any. My selected starting point was closer to closed because of the very light rear of the old PU . My coupe waas some what different (more weight on the rear) and a 41 Ford was even closer to the mid range.

Trees
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