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By Florida_Phil - 5 Years Ago
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My 1955 Thunderbird has stock drum brakes and a dual drum brake master cylinder. I rerouted the brakes lines without a proportioning valve. I rebuilt the stock brakes from front to back and adjusted them as close as possible. My pedal is firm and high. These brakes are less than adequate for today's traffic. I see all kinds of front disc brake options from Granada spindles to high dollar kits. I don't want to change the front steering geometry. I wish to run stock 15" steel wheels. I may upgrade to 15" aluminum wheels in the future. Do I need power brakes as well? What is the best option for my money?
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By miker - 5 Years Ago
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Best option for the money is kind of a value statement, as opposed to “cheapest”. My bird has a front disc kit from 1999 or so, from a bird suppler. It consisted of a small spacer on the spindle, bearings, a Granda rotor with the hub turned dow to fit early wheel center, brackets, and an early Fairlane caliper. Misc parts and the dual master for disc/drum. The spacer (used to fi the new bearing stack) moves the front wheels out maybe 1/8”. Not a problem.
I don’t remember if mine had replacement rear cylinders,I know some available now do for brake balance. I used a separate rear proportioning valve not a combination valve.
They work fine, but you might want to look at the quality and type of front pads supplied. Mine were hard pads to go high miles, and took a lot of pressure to stop hard.
The Granda spindles require reaming the (IIRC) the lower ball joint, and lower the front, so you’ll probably need blocks in the back.
I prefer the Aerostar springs, and it’s been reported using both goes too low for most people.
I’ve also got rear disc, and I wouldn’t do that again. I’d fit the later model self adjuster to the rear drums. The ability to modulate the brakes right at lockup still isn’t like a modern car, so the expense wasn’t worth it. If you’ve got the money and engineering experience to do a full design using Wilwood or such, that would probably change.
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By oldcarmark - 5 Years Ago
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Florida_Phil (2/6/2019)
My 1955 Thunderbird has stock drum brakes and a dual drum brake master cylinder. I rerouted the brakes lines without a proportioning valve. I rebuilt the stock brakes from front to back and adjusted them as close as possible. My pedal is firm and high. These brakes are less than adequate for today's traffic. I see all kinds of front disc brake options from Granada spindles to high dollar kits. I don't want to change the front steering geometry. I wish to run stock 15" steel wheels. I may upgrade to 15" aluminum wheels in the future. Do I need power brakes as well? What is the best option for my money?
I don't have a specific recommendation for Disc Brake Conversion Kit but keep this in Mind. Any Kit that uses Granada Spindles will lower the Front End by about 2 Inches. There are Kits that keep your stock Spindles and use a Bracket to mount the Calipers. If You don't want to go lower find a Kit with the Brackets. Wilwood has such a Kit as well as several other Suppliers on the Web. When I did my 56 10 Years ago I used Granada Spindles and I had to source the Parts required to complete the upgrade as well as find someone to ream the Lower Holes in the Spindle. Now a complete Kit is available with brand new Granada Spindles already machined. If You are going to change to Discs find a Booster or Booster/ Master that works on 55 T-Bird. You will find a big difference in the Braking using Discs and a Booster. I know I did..You will also want to ad Self Adjusters to rear Brakes to keep them in proper Adjustment. Very important when You have Discs on the Front.
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By Florida_Phil - 5 Years Ago
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Thanks for the reply. The issue I keep struggling with is how much modifying is too much? I know I can turn my '55 TBird into a modern car by replacing everything but the body. If you have been watching the auctions lately, you will see the big bucks are being brought by resto mods. It seems the younger folks want old cars that drive like new cars. I bought my car so I could have the car I would have had in high school if I had the money. My car is an early sixties hot rod Thunderbird. It's been modified, but can be turned back to stock if someone wants to go back. If I put Granada spindles on my car will it reduce it's value? How about electric power steering, a 5 speed or a 9 inch rear? I think early TBird should have Y blocks. Others may think differently. We or someone close to us is going to have to sell these cars some day.
The power disk brake kits I have seen require moving the battery to the trunk. Anyone done this?
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By KULTULZ - 5 Years Ago
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It's been modified, but can be turned back to stock if someone wants to go back. If I put Granada spindles on my car will it reduce it's value? How about electric power steering or a 9 inch rear? I think early TBird should have Y blocks.
Simply keep, box and catalog take-off parts. The future buyer will have his choice of how he wants the car.
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By miker - 5 Years Ago
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The typical disc/drum bird coversion with power uses the original type booster only for the front disc. The rear drums remaim manual. I’ve had that, it work fine. For 4 wheel disc I used a hydroboost, it clears the hood latch and battery. It does require the power steering pump. One of those cases where one thing leads to another.
To me, given your comments, the kits the bird suppliers sell (Larry’s still sells them, I’m sure others do) would be your best choice. The oem style booster, stock spindles, all bolt on. Your choice of power or manual. There’s many articles over at the Ford Barn on what you need for the self adjusting rears, and it not much money or work. As K points out, keeping the rear adjusted is really important with the conversion.
I’ve put many front disc conversions on vehicles, and on the birds I’d go with the long time thunderbird suppliers. Many of those other companies sell parts that bolt up, but don’t work all that well together. Been there, too.
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By Florida_Phil - 5 Years Ago
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These kits do not include a proportioning valve. If I am only going to convert the front to disks, do I need one? I used one on a Granada spinal 1965 Mustang front disk conversion I did years ago and it didn't seem to do anything.
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By DryLakesRacer - 5 Years Ago
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Phil, Consider contacting Prestige Thunderbirds in Santa Fe Springs California. I've seen their kit which includes 4 piston front discs instead of normal 2 piston. They have also perfected the use of our power assist units with a dual master cylinder. They also have a catalog. At a recent Thunderbird show I saw their units on quite a few 55-57 Birds and they had a rep there.
Since I am local I went to their business and talked to the owner and was very impressed. They are definately not a start up business. They also have a website. It's the kit I'm going to use on my full size 56 car because many of them don't use the power assist and suggested I don't at first. Good luck..
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By miker - 5 Years Ago
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Prestige has been around a long time, I had one of their soft tops. If DLR has seen the plant and is sold, then I’d second it.
On the proportioning valve. If you’re going to play around with the wheels and tires or lower the car, the braking balance might change a bit. Enough to notice, I don’t know. I just prefer to put the valve in when the brakes are apart so it’s there if I need it. I hate bleeding brakes.
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By dbird - 5 Years Ago
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As you're interested in keeping stock height, you could also consider Scarebird. I used their brackets a few years ago with only minor problems, mostly adding a washer outside the bearing so the cotter pin would work. Lincoln rotors with C10 calipers. You'll have to turn down the rotor hub to make stock wheels fit. While many cars have been sold with discs but non-power, as in countless British cars from the sixties, you may not need power. I used this booster, https://www.thunderbirdbrakeparts.com/proddetail.asp?prod=9795tb, which definitely required moving the battery. Some regrets on that as the battery does take up a fair amount of room and we go on more overnights than I expected while building the 'Bird.
X2 on what Miker said about converting the rears to self adjusting. I did that when I switched to discs years ago and the car still stops straight with no drama. You can find information on this site, or I think I have a couple of articles on it.
Don Wigle
55 Thunderbird, 56 F100 project still in progress.
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By DryLakesRacer - 5 Years Ago
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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.
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By KULTULZ - 5 Years Ago
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A brake PROPORTIONING VALVE is not designed to control front to rear brake bias.
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By miker - 5 Years Ago
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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
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By KULTULZ - 5 Years 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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By miker - 5 Years Ago
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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.
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By paul2748 - 5 Years Ago
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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.
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By charliemccraney - 5 Years 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.
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By KULTULZ - 5 Years Ago
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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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By KULTULZ - 5 Years Ago
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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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By slumlord444 - 5 Years Ago
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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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By KULTULZ - 5 Years Ago
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Everyone uses a dual master cylinder. No way for this to look right under the hood.
You're right, especially on a dedicated restoration.
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?
Yes, but you are giving up the safety feature of the dual reservoir MC.
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.
The dual reservoir MC is a safety feature. Depending on what part of the hydraulic system fails will dictate as to how the system reacts. The system is meant to be able to get off the road with a somewhat safe stop. It is not intended for continued driving
An operational safety brake is paramount as you have no idea what to expect with a hydraulic failure, especially if a PDV (pressure differential valve) is not used with the swap to isolate the failed system (front/rear or possibly both) and give the driver a warning lamp indicating a system failure.
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By KULTULZ - 5 Years Ago
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Valves FAQWhat does a proportioning valve do?
A proportioning valve is used in the rear to decrease the rate of pressure rise to the drums relative to the pedal force as weight is shifted to the front during braking. This prevents the rear from locking up under hard braking conditions. What are the symptoms of a bad proportioning valve?
If your prop valve has gone bad your rear wheels will lock up easily, especially on wet surfaces. What does a metering valve do?
A metering valve or "hold off valve" is used in the disc portion of a disc/drum system to hold off the application of the front discs slightly allowing the slower reacting rears to catch up. This provides rear stability on wet surfaces and reduces excessive pad wear. What are the symptoms of a bad metering valve?
Your car will nose dive and the front pads will wear too fast. What does a residual valve do?
There are two different uses for residual valves. The 10 lb valve is used to hold a residual pressure to the drum brakes to keep the shoes out close to the drums giving a higher firmer pedal. The 2 lb valve is used in the disc when the master cylinder is lower than the calipers to prevent back siphoning of the fluid from the master. What are the symptoms of a bad residual valve?
The brakes will be very spongy and you will need to pump the pedal to get good brakes. What is a combination valve?
A combination valve incorporates metering and proportioning into one valve providing all necessary valving for disc/drum systems.
See below Should I use an adjustable proportioning valve?
Not if you can help it. The adjustable valve will only provide the proportioning function and not the metering that is needed.
SOURCE- https://www.mpbrakes.com/page.asp?p_key=AD8E13B3C7E0409FB4FF6C7C7267C59A
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By charliemccraney - 5 Years Ago
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There is more to a dual master cylinder than simply bolting one on to get the safety feature. I know because I had a rear brake line leak that resulted in no brakes at all. I don't know what else is required but do not let it give you a false sense of security in a non stock application.
I was fortunate to realize I had the problem in my driveway.
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By Florida_Phil - 5 Years Ago
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Great resource. Answers all questions I had. Thanks!
https://www.mpbrakes.com/page.asp?p_key=AD8E13B3C7E0409FB4FF6C7C7267C59A
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By KULTULZ - 5 Years Ago
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| charliemccraney | Posted 10 hours ago
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| There is more to a dual master cylinder than simply bolting one on to get the safety feature. I know because I had a rear brake line leak that resulted in no brakes at all. I don't know what else is required but do not let it give you a false sense of security in a non stock application.
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Just wondering. With your install, did you include a Pressure Differential Valve? It has a provision for a sending unit to trip a warning lamp in the cabin in case of a failure?
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By KULTULZ - 5 Years Ago
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slumloard44 Posted -
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 booster work with front disk brakes and a proportioning valve?
Forgot to answer this question.
In short no. It cannot be done with the OEM MC. The MC will not supply either enough pressure or volume to the calipers.
Now, if you wanted to maintain a somewhat OEM appearance for a DISC/DRUM conversion w or w/o a booster, FORD used a single reservoir dual outlet MC in 1965/66 that allowed DISC/DRUM w or w/o power assist and the reservoir was much larger to supply the needed volume for the calipers. These were referred to as 'FRUIT JARS' if you remember that far back.
If planning to use the OEM MIDLAND BOOSTER, only the FRT disc line could be routed through the booster slave cylinder (either w DUAL RSVR MC or the SGL RSVR DUAL OUTLET) as the two systems have to remain isolated from one another.
You only need power assist on the FRT DISC as they require more pressure/volume over drum. The rear drum will work fine with manual pressure.
IMO, a late/early seventies DUAL RSVR MC is not that noticeable if FORD (BENDIX) design. If you need to stay with the OEM MC, you could juggle shoe size/wheel cylinder size to make the drum brakes more aggressive.
Hope all of this made sense.
Now all of the above is IMO, and you need to verify before attempting.
EDIT -1945 HRS 2/11/19
The above text was changed somewhat hoping to make it more understandable.
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By charliemccraney - 5 Years Ago
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There is no pressure differential valve in the system.
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