So i just finished running all my brakes and such. Now im having some troubles. I have heard some conflicting stories about weather i need a proportioning valve or not. Ive bled tons of brakes and never had a hard time like this before. Here is what i got_______________________________________________ disc/drum GM combo valve (proportioning valve) duel master cylinder and brake booster So here is my problem, im trying to bleed my rear drums first starting with the furthest away from the MC. I have a vac bleeder which i love but heard to try to gravity bleed my system. I pushed in the pin on the GM prop valve and still nothing. Getting frustrated just a bit. When i initially started looking around town for the GM prop valve i had a hard time finding one. I finally found one off a buddies S10 that was headed for the wrecking yard. No one seems to know why but local part shops dont want to sell these combo prop valves anymore. Any one know why? i have an Adjustable prop valve too sitting on my shelf. I was told that those GM prop valves are junk and i could just put the adjustable one in its place going to the rear drums. Personally id like to keep the combo prop valve. but im just a little frustrated i cant get brake fluid to the rear drums which im told is due to the proportioning valve and that stupid push button.
Well, the combo valve does a combination of things - hence the name 1) turn on warning light when one half of system quits working. Most people never hook up and don't have a warning light 2) Hold off front brake pressure for 75-125 psi while rear shoes overcome spring pressure. Mostly a wear tuning tool for the factory - don't need for our cars (this is that pin you are pushing...) 3)Limit/proportion rear pressure to avoid rear brake lock-up at high "G" stops - you need this with front discs and rear drums. But, GM prop valves can be from 250 psi to 600 psi or more, so really needs to be tuned to the car (brake size, tire size, weight distribution, etc) . This is why I always recommend and use an adjustible prop valve instead of a combo valve. So bottom line - ditch the GM combo valve and use the adjustible - and adjust it to limit rear lock up on slippery as well as dry roads (use old tires..... ) I suspect auto parts stores don't stock them because they are very reliable and rarely go bad , there are many part numbers to carry, and they getting to be very old parts ..........heck, most auto parts places only carry the very high volume parts - see your dealer for anything else !
What kind of master? Corvette style? I had mine plumbed up backwards and had to switch it around yesterday. I say run the adjustable valve. Here's my thread from the other day: http://www.jalopyjournal.com/forum/showthread.php?t=665336
http://www.speedwaymotors.com/Dual-Brake-Booster-and-Master-Cylinder-Combos,5084.html Its mounted on the firewall so i didnt think i needed any residual pressure valves in line. i think im going to get rid of the GM style and go with my adjustable one. this is the adjustable one i have. http://www.speedwaymotors.com/Wilwood-Knob-Style-Proportioning-Valve,6494.html
Wish me luck, im ditching the GM prop valve and going with my adjustable one. sounds like unless your gonna use that brake light its not really necessary.
Stick with the rite GM Proportioning valve, I have never, ever seen the adjustable ones do any good at all, waist of time. Not knowing the dia. of your M/C and wheels cyl. weight of vehicle front and rear, tire dia. I can't tell you what the rite one is. I would check rod travel and pedal ratio first. You may also need a Combination valve instead of just a proportioning valve, do a search on both.
are you kidding? i have done probably 10-15 brake conversions, rear disc conversions, brake swaps etc..... and a 35 dollar brake proportioning valve makes a WORLD of difference with brake bias. after setting up everything and doing some heavy braking on slippery pavement, you can make a car/truck stop with authority. OP, summit has some very reasonable singles/duals/ and duals with brake pressure sensors built in. http://www.summitracing.com/parts/WIL-260-11179/?rtype=10 is a simple disc front/drum rear valve that makes life easy. and the factory valve, the pin got pulled OUT to bleed, if i remember correctly.
GM style valve...Only problem I saw was having a couple of them leak,...and we maintained a 1,200 vehicle fleet. To bleed brakes, I made a tool to put in place of the warning light switch, and that keeps the valve centered during bleeding. When finished, be sure to re install the switch. 4TTRUK
The last handful of rods I built for customer were disc/drum set ups and I did install the Wilwood adjustable P/V to rear ONLY because if you don't AND have problems you can tell the customer you did it by the book, especially if you have a customer that reads to much! These valve will not "help" you get any more fluid out when bleeding. Each coupe/roadster I took out for a shake down cruise with knob set mid way on a dirt road, hit the brakes, knob all the way in, all the way out absolutely no diff. in breaking, none, nadda, zip............... I have 3 on the bench now, that's why they are on the bench and not on the vehicle.
i think we crossed wires here- i agree it will not help with bleeding, and agree with what you are saying
Thanks for the link to the NEW style to me P/V from Summit (Wilwood shown below), in all fairness I never have used that particular one, only the older type with in & out......
While we're on this subject, may I hyjack a bit. I'm going disc/disc with a corvette manual master. I don't think I need residual valve, correct? I will need porportioning valve for frt to back bias, correct? Thanks.
I've installed a ton of these. They work well, and eliminate excess connections, and possible leaks. I strongly believe that every non-factory brake setup needs a means of adjusting brake bias. As for residual valves, I put them in everything, no exceptions. The longer it takes to get the pads or shoes to the braking surface, the farther you travel. Not good.
you know- plumbing gets REALLY easy when you use this: http://compare.ebay.com/like/280814010418?var=lv<yp=AllFixedPriceItemTypes&var=sbar&_lwgsi=y&cbt=y plastic brake lines. lots of racers use it, its cheap/light/easy to use/ works great.
I have installed over 100 10psi residual valves on rear drum brakes. No smoking, at all. Please explain yourself.
you are exactly correct with drums....... he was stating disc brakes in the rear (or thats what i was reading "disc/disc with corvette master") im sure you know, residual valve on disc brakes makes them drag.
I install 2psi residual valves on ALL of my disc brake installations (over 100), and have for over 15 years. Zero problems, no smoking, of the brakes, or otherwise.
2psi isnt 10psi, you know that. also, depending on where the master cylinder is, is going to determine if you need the residual valve or not as well. i guess i need to clarify myself more: yes, a 2psi residual valve works- but isnt 100% necessary for disc brake operation (taking into consideration where the master is) no, a factory residual valve for rear drum brakes on a rear disc conversion will not work. and clarifying using factory or aftermarket residual valves and intended purposes would help with both parties as well no harm/no foul between us, ya?
No harm or foul, but we need to make sure that what is shorthand for us is conveyed to the rest of the folks in a manner that is clear and easy for them to understand. If we (us, or ANY of us on the board) leave out detail, especially on things like braking systems, things could get ugly. Nobody wants that.
OK, you guys are on the same page but now I'm falling behind. Corvette manual disc/disc master on the firewall. I don't really see why a residual would be needed.
In the case of a disc master cylinder on the firewall, a residual valve, on either circuit is not strictly required. I install them anyway, but others don't. I prefer that there is the 2psi pre-load on the system. It keeps the rotors clean, and the pads close, cutting response time, by a few milliseconds. That's my take. Your mileage may vary.
It has been my experience that even with a Corvette M/C, front and rear disc, you will still need a combo/proportioning valve, or a hold off (stand off ) valve (front) that will let the rears work a millisecond before the fronts to eliminate the "nose dive effect" with out one, giving better control when breaking.
correct me if im wrong, but it was my understanding that master cylinders were built with the rear circuit closest to the firewall on purpose- having the rear circuit in the back, it was able to apply pressure to that circuit first to minimize front end "dip"
It gets real confusing doesn't it! The last aftermarket Vett M/C I tore down had two main springs, plungers and seals as most duals do. You could tell that the springs were of different "rates" which I took as another way to time the bias................
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