proportioning valve questions..., that a search didn't help. |
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proportioning valve questions..., that a search didn't help. |
red914 |
Dec 30 2004, 10:07 PM
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#1
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...i believe in coyotes and time as an abstract... Group: Members Posts: 862 Joined: 8-February 04 From: poulsbo, washington Member No.: 1,641 |
so, what can be done about the rear brake proportioning valve? it seems most people replace it with a "t" fitting, but that doesn't seem to address the issue. it must be there for a reason. can it be rebuilt? can it be replaced? how can one tell if it is working properly? what is the best way to bleed the little beggar? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)
i appreciate all the help and information. soon i'll be able to tackle the brake project, now that the holiday vortex is loosening its grip on my life. |
airsix |
Dec 31 2004, 12:25 PM
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#2
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I have bees in my epiglotis Group: Members Posts: 2,196 Joined: 7-February 03 From: Kennewick Man (E. WA State) Member No.: 266 |
Even perfectly bled 914 brakes will have some spongyness due to the proportioning valve. Why? Because as you increase brake pressure you compress that huge spring/piston in that huge tube and thereby displace a HUGE volume of brake fluid which is directly translated into additional peddal travel. Since you are basically compressing the proportioning valve spring with your foot, it feels mushy. You could almost say it was designed to be mushy. (IMG:http://www.914world.com/bbs2/html/emoticons/barf.gif) Some people go with a 'T' and eliminate all of the mushyness attributable to the proportioning valve. I like to maintain some adjustable bias so I used a Willwood adjustable valve. It does the same thing as the stock valve but the volume of fluid it can displace is very small, so it doesn't feel mushy. It's a compromise. It's not as firm as a 'T', but almost. I mounted it in the stock location so I have to adjust it from under the car and then leave it the heck alone. If it was in the cockpit I'd be messing with it all the time. (Same goes for my boost adjustment)
-Ben M. |
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