Rear Brake Project


The purpose of this project is to find a more  
precise method for adjusting the rear
brakes and thereby significantly reducing
brake pedal travel.

That being said, I have tried to emulate the setup
on the Triumph Spitfire. The diagram on the right shows that the location of the clevis (14), which attaches to the  E-brake lever,  can be adjusted  relative to the  E-brake cable. This locates the
leading brake shoe and wheel cylinder, relative to the drum.

There is also a return spring to help ensure the
release of the emergency brake.
ebrake

The prescribed method for adjusting rear
brakes is to adjust the emergency brake
cable under the armrest. This alternative
method allows fine adjustments at the
wheel.

Keep in mind the following points.
1. The brake system must be in good working order.
2. The wheel cylinder is designed to float in the backing plate.
3. The "adjusting nut" provides an appropriate lower pivot point for the shoes and
    "centers" the wheel cylinder.
4. The E-brake lever shifts the wheel cylinder and shoes forward, so that the leading shoe
engages the drum with minimum pedal pressure.
5. The single piston wheel cylinder then shifts rearward, pushing the rear shoe against the drum.
6. This non-intrusive modification is only a test to find a better way to adjust the
rear brakes.
 Click to enlarge
thbrake1
thbrake2
thbrake3
Before
After
After
    

The modification is as follows;
1. Secure a wire to the e-brake cable abutment as shown above.
2. Invert the cable/lever clevis pin.
3. Run the wire through the clevis pin.
4. Adjust the wire length with a collar so that the shoe is just off the drum.

Brake pedal travel is now about 1.5", down from 2.5".
Collar is from leftover R/C car parts.
The large spring (see photo) ensures that the E-brake lever returns to the disengaged position.

Text from the workshop manual

REAR BRAKES ADJUSTMENT

    
To ensure the correct operation of both the rear brakes and the handbrake the under mentioned
adjustment procedure should be adopted:
       1. Raise the rear of the car and support on blocks.
       2. Disconnect the handbrake cable at the clevis connections on each rear brake backplate.
       3. Using the brake adjusting screw, turn clockwise until the wheel locks. The wheel should of
course be rotated slowly during this operation. Back off' the screw 2 notches ONLY. The wheel
should now be free to rotate without undue binding of the shoes in the drum. Ensure that the wheel
cylinders are not being held in the 'on' position by the bundy pipes.
       4. Re-connect the handbrake cable clevis connections and
adjust the handbrake intermediate
cable, so that with the handbrake lever in the fully released position, the handbrake is just on the
point of coming into operation.


Update...Upon replacing the brake hoses, there is a dramatic improvement pedal firmness and a bit more reduction in pedal travel.



tinyHOMEtiny3