Thread: brake line question

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I have another brake line question regarding my 65 chevelle. The car has drums all around, power brakes, and has a dual reservoir master. Does any one know how to route the lines form the master cylinder and into the propotion valve? Does it even need a proportion valve? A picture would be great. Thanks guys.

Yes you need the proportioning valve to prevent premature rear brake lockup.
You can install an adjustable proportioning valve from Wildwood, that way you can adjust your brake effort with ease.
Front line from master cylinder goes to proportioning valve, and then to rear distribution block, and out to brakes.

This is borrowed from The "Hambs"....

BRAKE PROPORTIONING

When designing and selecting a braking system for your machine, there are things you gotta know. Locking up the rear brakes only produces a condition which results in a partial or complete loss of control. This condition is very unstable and the car could easily go into a spin. On the other hand, locking the front brakes only produces a stable condition in which the vehicle travels in a straight line. In this condition there is almost complete loss of steering control. If all four brakes are locked, it produces a condition which is fairly stable, resulting in the car traveling in a straight line.

It is safer to lock the front pair of brakes if we must lock a pair of wheels. Taking into consideration the vehicle weight transfer to the front wheels when braking, a rule of thumb front-rear braking percentage ratio has been formulated. A 60% front and 40% rear braking ratio is used in general with 65/35 distribution for competition and sports cars. This means that 60% of the braking is designed into the front brakes and the remaining 40% in the rear.

The 60/40 ratio is a compromise under ideal conditions. Not so ideal is mud, rain, or ice where the coefficient of friction between the tire and road are less than desired for maximum deceleration rates, and the front wheels will tend to lock up. The coefficient of kinetic friction (skidding tires) is always less than the coefficient of static friction (non-skidding tires). The maximum rate of deceleration is just before the wheels start to skid, and when they do, you lose about 25% of the stopping power. It's the grip of the tire on the road that actually determines how fast a car can stop, even though you can lock your brakes.

The problem of weight distribution and weight transfer during braking is very important. The braking force of a wheel is related to weight on that wheel. It is the ratio of the center of gravity height to the wheelbase length that determines how much weight is transferred to the front wheels during braking. Long wheelbase and low center of gravity tend to reduce dynamic (movable) weight transfer. If a brake system is not designed for this weight transfer, serious problems can result.

Various methods used to produce a higher braking percentage on the front end, but not necessarily limited to only these, include:

1. Use of larger wheel cylinders on front brakes than on rear.

2. Use of wider brake shoes in front than on rear.

3. Use of brake shoe material with higher coefficient of friction on front brakes than rear.

4. Use of a brake shoe actuating design which features servo action, such as the Bendix 2 shoe, single anchor, self centering type.

5. Use of smaller total diameter wheel in front or larger wheel in back, or combination of both.

6. Use of larger diameter brake drums on front than back.

7. Use of pressure proportioning valve between the front and rear brakes.

When disc brakes are installed on a front end with drum brakes on the rear we arrive at a new set of problems. There is no servo action in a disc brake which requires high hydraulic line pressure and heavy pedal pressure. Even with a proportioning valve, the distance between the brake pedal axis and the master cylinder pushrod pivot may have to be shortened to gain leverage for higher line pressure. Disc brakes lack instantaneous gripping at low speed and do not decelerate any faster than drum brakes. Their main advantage is that they are fade free, whereas a drum brake system will fall off in performance as brake fade sets in.

In spite of proper proportioning, brakes too small won't work satisfactorily. If the disc rotor is too small in diameter or the drum brake too small in total drum swept area, brake fade is unavoidable. Brake fade is caused by excessive heat retained in the brake system.

All brake systems must be large enough and have sufficient mass to absorb the heat generated in an emergency stop from high speed. It is impossible to dissipate the heat as fast as it is generated, but the system should be able to keep the drum temperature down within reason and dissipate enough heat between brake applications to avoid fade.

The idea behind drilling brake drums and backing plates is for air circulation and cooling, but it doesn't work too well. Drilling reduces a mass of metal and the heat is not conducted away from the interface, the line between the brake lining and the brake drum, as quickly as it normally would be. The holes will pick up sand and grit which accelerate brake wear appreciably. Brake efficiency will be increased and brake cooling accelerated by leaving the brakes undrilled.

Aluminum paint on brake drums does not accelerate heat transfer. The rate at which heat is dissipated from the brake drum depends on the heat emissivity characteristics of the brake drum surface. Rusted iron has the highest rate of heat emission. Aluminum paint acts as a highly-efficient heat insulator by reflecting the heat back into the drum. Do not paint brake drums for optimum efficiency. If you do, paint them black.

Difficulty arises when trying to figure a sufficient brake size necessary to avoid excessive heating because of many variables. Much of the work is trial and error. When selecting brakes, comparing total brake lining is not a good way to judge brake system efficiency. The total swept drum area is much better method of indicating braking effectiveness.

This is only meant as a reminder and guide line and barely touches the surface. Don't neglect to do your own research on the system you want to use and how to use it. No matter what you might think, the brakes are the most important system on your car. No matter how fast it goes, the car won't be worth much if you can't stop it.

Thunderbucket, Very nice dissertation, A+.

Wish i could take credit for the disertation,,,but i can't,,,,i reposted it from the "Hambs"

Why you slimy plagerizer!!!

May the fleas of a thousand camels infest your nostrils...

Oops, I didn't see that at the top..

Still a good piece there.