Residual Brake Pressure Valve

[EcoBeast1835]

I have been working on converting my 60 bird to front discs and have a question. I was looking through NYsquarebird58's topic on how he did it and in it he had some pictures of some 10psi residual pressure valves. are these needed? I have the same proportioning valve and the same style master cylinder.

I am used 78 granada spindles and stuff in the front, stock rear drums, looks like the the same proportioning valve as NYsquarebird58. the power brake booster is a 7inch dual diaphram universal and the master cylinder is a RPC gm style.

[simplyconnected]

You have a choice. The idea is to keep your rear shoes adjusted close to the drums. Two methods prevail, self-adjusters or residual valves.

Now we get to 'personal preference'...
When self adjusters work as they should, nothing is better because they actually turn the star wheel which expands the shoes.

Residual valves simply prevent the shoes from retracting by keeping ten psi on the hydraulic line. That means the pistons keep extending, and extending as the shoes wear. Eventually, a piston may pop right out of the bore. Yes, I've seen it happen. That leaves the rear brake circuit inoperable (with a soaking mess of brake fluid inside one drum).

11" self adjuster kits are very inexpensive and available at just about all auto parts stores. That is what I use. - Dave

[simplyconnected]

This topic reminds me of a Ford Tempo I owned (and loved). The brake self-adjusters expanded the TOP of the shoes so that the wheel cylinder pistons continued to travel farther and farther until one of them came out of its bore. I looked at that and wondered how Ford could have reverted so badly in brake engineering. There was still quite a bit more shoe left, enough for well over a year of service, so I tack welded a small 'shim' to the bottoms of both shoes (which simulates the old way of expanding the star wheel).

I mulled this situation around in my head, found that MANY Tempo cars had the same situation and I thought of the consequence: Since the system is a 'dual system' you still have at least some brakes. Some people would need to tow their car to a garage, new brake shoes were certainly purchased, the system got new brake fluid and probably new wheel cylinders. The owner would gladly wait and gladly pay the going rate because brakes are so essential and some folks could be made to feel guilty for not checking their brake wear more often. This makes it 'the owner's fault' while the mechanic is going to 'save their car'. With the 'old system', after the brake linings were gone, a horrible metal-on-metal scrape would develop but not in this system, so there is no warning. Anyone would freak out seeing ugly brake fluid coming from a rear wheel. It's simply a money generator and people won't complain.

Soaked brake shoes can be restored. Brake linings get EXTREMELY hot under normal use. Heating the soaked linings causes the brake fluid to bubble out. Some guys use their kitchen oven. I use a propane torch right on the linings. When more fluid comes out, I use a paper towel to wipe it off, over and over. Eventually, the brake lining will turn colors from dark to gray, just like new shoes. They work just fine and they're already 'bedded-in' so no break-in is necessary.

Now you know why I won't use a residual pressure valve on shoe brakes.
Also... DOT-3 brake fluid WILL take the paint off your car. What they don't talk about is, DOT-3 is glycol-based and plain water will wash it away immediately with no harmful effects. - Dave

[newstang]

The other option is inexpensive to go to rear disc.
I use these on all my mustang builds, it would be the same for tbirds.
this guy makes adapter spacers so you can use lincoln town car or marquis rear disc brakes which are readily available and cheap.

https://www.ebay.com/itm/1965-1973-Ford-Mustang-Rear-Disc-Brake-Conversion-Adapting-Parts-9-8-Spacers-/324187328852?hash=item4b7b121154

[simplyconnected]

With all due respect, here's the problem I have with rear disc brakes... Rear drum brakes work just as well and they already come on our classic Ford cars.
My wife's 2010 Ford Escape came from the factory with disc/drum (ABS). Why? I think the answer is, 'why not?' Rear brakes only perform about 25% of the total braking power and I've never had a rear brake fade. Mashing the brake pedal makes the car's weight dive forward exerting more load on front brakes and less load on the rear, which is a great reason for front disc brakes.

newstang, the spacers you suggest are only a small part of the rear disc retrofit. The eBay description suggests this retrofit will cost about $200 and the emergency brake system must be purchased and retrofit as well. A mechanic would probably charge far more than $200 to install it. I have no problem with pruning the axle flange with a cutoff wheel but there is an issue with wheel fitment which may cost an additional $200. Now, we're at $600. Is it worth it? Maybe for a Mustang or a Cobra but not a classic full-size Ford.

All Squarebird brakes are 11" in diameter. Once the front brake shoes are removed for the disc brake retrofit, they can fit the rear. In 1961, Thunderbird added self adjusters to these same brakes. The self adjusters come in a RH and LH kit and each costs between US$6.50 - $8.23 for each wheel (depending on whether you like Rabestos or ACDelco at Rockauto.com). They are also available in local auto parts stores under additional brand names.

My suggestion is to buy these self adjusters for Squarebird rear brake shoes (for under $20) and keep the emergency brake, stock. Our '59 Galaxie has front disc/rear drum brakes and I have no problem locking up all four wheels in a panic stop. I use a two-stage 8" booster, a 1" bore dual-piston M/C and a combination proportioning valve. The front pads fit S-10 or S-15 (GM) calipers and now, I have more rear shoes than I will ever wear out. - Dave

[newstang]

Thats great info, Im gonna retrofit the drums with the self-adjusters. Way cheaper.

[newstang]

I got the adjusters, anyone have a diagram of how it goes?

[jopizz]

Here are some pictures. Did you get the blue adjuster springs. They do not come in the kit. You have to buy them separately.

John

[newstang]

Here are some pictures. Did you get the blue adjuster springs. They do not come in the kit. You have to buy them separately.

John

ah, no i didnt. where do i get them and for what application.
thanks!

[jopizz]

The part numbers are Wagner/Duralast (Autozone) H412 and NAPA UP80509. They fit many different cars. They come two in a pack to do two wheels.

John