1966 WM300 Disc Brakes front or rear?

[Bob2]

After having to rewire the truck, ( instaled a modern harness with fuses) I am now contimplating on installing disc brakes after rebuild of axles.
Do to funding issues (don't we all) I will only be able to purchase one kit at a time.
Which axle would it be most adventagious to install on front or rear? Additionally will it be necessary to install a new master cylinder or, can I use the existing one and pedal. I would like to keep the stock look but with safety upgrades.

[Gordon Maney]

After having to rewire the truck, ( instaled a modern harness with fuses) I am now contimplating on installing disc brakes after rebuild of axles.
Do to funding issues (don't we all) I will only be able to purchase one kit at a time.
Which axle would it be most adventagious to install on front or rear? Additionally will it be necessary to install a new master cylinder or, can I use the existing one and pedal. I would like to keep the stock look but with safety upgrades.

The front is where you would want the disc brakes. Due to weight transfer, the front is where most of the braking requirements are located.

Your current master cylinder has a residual valve, due to the truck being fitted with drums. A disc system can't tolerate residual pressure.

Residual pressure keeps a very low pressure present in the system, primarily and originally intended to keep out atmospheric pressure, meaning... really.... air and moisture.

Residual pressure will not apply a drum brake due to shoe return springs. That low pressure does not create nearly enough force to overcome the springs.

A disc system has no return springs. If you have residual pressure you will drag the disc pads and dramatically reduce the life of the brake assemblies and possibly ruin the rotors.

Others here have gone this disc route and may chime in regarding their particular situation. Some go to a dual reservoir, dual circuit, master cylinder, with the accompanying safety advantage.

You may also enjoy the benefits of a vacuum brake booster.

[maineSS]

You'll want to remove the Residual Pressure (RP) valve from the master cylinder and install an inline version in the rear line if you keep drums in the rear. The RP valve in the PW OEM master is the little rubber flap over the perforated plate at the front of the cylinder, remove it BEFORE your 1st disc brake road trip (Don't ask how I know this).

[Bob2]

Disc Brakes

So, is more of a problem to install disc brakes, master cylinder, proportining valve, new tubing etc.

I intend to use the truck on backroads and dirt roads not on the interstate or major highways, just sticking to the less stressful roads.

Is there a good book on how to adjust the drum brakes properly, to have safe stopping or, is there a thread in these forums discussing the procedure?

Bob H.

[Frank Irons]

So, is more of a problem to install disc brakes, master cylinder, proportining valve, new tubing etc.

I intend to use the truck on backroads and dirt roads not on the interstate or major highways, just sticking to the less stressful roads.

Is there a good book on how to adjust the drum brakes properly, to have safe stopping or, is there a thread in these forums discussing the procedure?

Bob H.

The best advice for adjusting the drum brakes can be found in the service manual. The stock drums are adequate for the type of driving you describe. Adding a brake booster will enhance your current brakes performance. I put one on my WDX and I could lock up all four wheels if I really stood on the brake pedal. The key, as you have noted, is to have the brakes properly adjusted. The bottom adjusters is what gives most people problems. If the bottom adjusters aren't set right you will not have enough shoe contact with the drum.

Frank

[maineSS]

If your driving includes lots of stop and go (like in town), you'll need good brakes. Today's cars stop stop a lot quicker than those of the PW's vintage, and even allowing lots of stopping distance doesn't work when people cut in front- then stop suddenly. Spend whatever time and money it takes to get good brakes- it's much cheaper than defending against lawsuits.

[PWFFnut]

A very close call

long be fore the internet and all of the help full advice I have got from here I up graded the master cylinder in My 56 PW by having it sleeved to 1inch bore than going through all fore brakes and adjusting them this gave my fairly good brakes today I took the booster off My parts truck & as soon as I have a look at it I am going to put it on My 56