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DryLakesRacer
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Group: Forum Members
Last Active: Last Year
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I think this is the reason Prestige figured out a way to make the add on vacuum booster work with a dual master cylinder. Many did not want the battery relocated in the trunk.
56 Vic, B'Ville 200 MPH Club Member, So Cal.
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KULTULZ
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Last Active: 2 days ago
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A brake PROPORTIONING VALVE is not designed to control front to rear brake bias.
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miker
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I guess I should have said “adjustable” proportioning valve. As opposed to combination valves, etc. Mine’s installed on the rear brake line and definitely controls the rear pressure, hence the brake bias. https://www.wilwood.com/MasterCylinders/MasterCylinderValves
miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ
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KULTULZ
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Group: Forum Members
Last Active: 2 days ago
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A proportioning valve is a pressure reduction device. It is typically installed in-line in the rear brake line to reduce braking efficiency and compensate for premature rear-wheel lockup; a result of incorrect front to rear brake bias. An adjustable proportioning valve permits incremental adjustments to fine tune brake bias. This ability to adjust front-rear brake bias is particularly important in race applications, as changing track conditions and vehicle dynamics usually require the brake bias be adjusted throughout the race.
If you significantly change your vehicles weight and/or chassis dynamics, such as is common with muscle cars, hot rods, street machines and customs; you will likely need to remove the factory proportioning valve and install an adjustable proportioning valve. The factory valve was designed for a specific weight car, on a specific tire, with a specific suspension system, and a specific amount of brake torque at each wheel. If any of these specifications have been altered, the factory valve will not allow optimum performance of the braking system by either limiting too much pressure, or not limiting the pressure enough. A Wilwood adjustable proportioning valve will provide easy adjustment to obtain the optimum pressure for your modified vehicle. Normally, you do not need to purchase a proportioning valve with Wilwood four-wheel disc brake kits. Wilwood manufactures calipers with the correct piston area for each application, our kits will work with your dual-chamber stock master cylinder and stock pressure limiting valve. There is no need to modify or remove the existing pressure-limiting valve, and no additional proportioning valve is needed. A Wilwood kit will also work with ABS control systems. This following text is also included in the Wildwood info page for their valves: WARNING - Adjustable proportioning valves are designed for tuning and balancing custom brake systems on performance, racing, and other types of special purpose vehicles. They are not designed as direct replacements for any OEM application. It is a disclaimer. They are saying if you bust your butt it is on you. ADJ Proportioning Valves are not DOT street usage approved. Balanced braking comes mainly from balancing components correctly. I am not jumping on you personally Mike, just letting it be known to others. Some of these so-called brake swap kits are dangerous.
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miker
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No offense taken, K. That’s why so many of the “cobble together” brake systems seem wrong to me. I’m fortunate in that I have a mechanic with considerable fabricating and racing experience to help me sort these kinds of problems out. I think sometimes people don’t appreciate the amount of engineering that goes into good factory systems. GM and Ford don’t list lord knows how many “combination” valves for different models because they aren’t needed.
I have Wilwood brakes on one of my resto mods. Done properly they’re great. Done improperly, who knows.
miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ
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paul2748
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Who told you that? How else do you adjust front back brake bias on a custom brake system. Tell the 1,000's of users who use them.. In a perfect world, every body can get just the right components - this is not a perfect world. KULTULZ (2/8/2019)
A brake PROPORTIONING VALVE is not designed to control front to rear brake bias.
54 Victoria 312; 48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ
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charliemccraney
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Group: Moderators
Last Active: 26 minutes ago
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My understanding of brake bias is related to how the wheels lock up under hard braking. If the fronts lock first, it's front biased. If the rears lock up it's rear biased. Is that correct? Assuming so, an adjustable proportioning valve is one way to adjust bias. Others could be wheel cylinders, brake pads, tires, weight balance, controlling weight transfer anything that would affect when the wheels lock up. The average Joe would use an adjustable prop valve and possibly brake pads.to try to get it right. Brake stuff is confusing. Even faq sections of one manufacturer can contradict others.
Lawrenceville, GA
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KULTULZ
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charliemccraney (2/8/2019)
My understanding of brake bias is related to how the wheels lock up under hard braking. If the fronts lock first, it's front biased. If the rears lock up it's rear biased. Is that correct? Brake stuff is confusing. Even faq sections of one manufacturer can contradict others. When brakes lock and the tire actually grabs the road surface, you lose steering control and the rear end may swing on you, especially on a wet surface. This why ABS came along. There is one kit manufacturer that defines the propositioning valve while actually describing a metering valve. They are all over the place. I hate to bring this subject up in a forum as it usually turns into a food fight. But anywho, I just wanted to bring this out.
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KULTULZ
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miker Posted
As K points out, keeping the rear adjusted is really important with the conversion.
That was oldcarmark Mike, credit where credit is due.
On a 55 FORD/BIRD drum brake, there is an eccentric on the FRT primary shoe that requires adjustment before the normal star-wheel adjustment is attempted.
I have also noticed the vendor who supplied a BIRD FRT DISC CONV KIT using no proportioning valve (with MIDLAND BOOSTER) is now supplying one with his kit. I understand the using of larger rear wheel cylinders to achieve somewhat correct brake bias but it still has to have a proportioning valve. The FRT DISC are much more aggressive that the original drum and the hydraulic LINE pressure will cause rear brake lockup more quickly with DISC/DRUM..
The use of a FRT METERING VALVE is also useful as it will somewhat delay the FRT DISC aggressiveness leading to a more balanced braking system.
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slumlord444
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Everyone uses a dual master cylinder. No way for this to look right under the hood. The '65 Mustang had a single master cylinder with power and non power brakes. Would the stock master cylinder and boster work with front disk brakes and a proportining valve? I realize the dual master cylinder is a safety thing but I had a rear break like fail with a dual master cylinder once and the emergency brake would have helped as much. I would have hit anything that would have been in front of me at the time anyhow. I have this obsession with keeping things looking as close to orginal as possible.
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