Most braking systems consist of front disc brakes located inboard on the driveshafts and rear drum brakes located on the rear hubs. Older cars have inboard front drums. The handbrakes on 2CVs, Dyanes etc. operate on the front wheels.The brakes are operated by a suspended brake pedal below the dash which operates a brake master cylinder, pushing fluid under pressure to the cylinders (or disc calipers) of the front and rear brakes. Front disc brakes are self adjusting (except as regards the handbrake - see below) and cars fitted with disc brakes use LHM fluid. Cars with front drums use normal DOT4 fluid. IT IS VERY IMPORTANT TO USE THE CORRECT FLUID FOR YOUR CAR. THE MASTER CYLINDER, WHEEL CYLINDERS AND SEALS ARE NOT INTERCHANGEABLE between disc brake cars and cars with front drums. If you change any seals or cylinders ensure that they are compatible with the brake fluid for your car, otherwise they will be damaged by the fluid resulting in a leak and possible brake failure. Master cylinders which use LHM are often painted green with a green fluid reservoir; those which use DOT4 are not usually painted. Rubber seals are used on the ends of the brake pipes (where they enter the wheel cylinders, the master cylinder, the 3-way union on the back axle tube and the disc calipers). Seals for drum brake cars (DOT4 fluid) usually have a red dot on the black rubber whereas seals for disc brake cars (LHM fluid) have a green dot. This may vary depending on the make of seals you buy.
(Refer to illustrations at the bottom of the page) Adjustment of drum brakes should be checked/carried out every 6 months or if pedal travel becomes excessive. The brakes are adjusted by turning hexagonal screws on the back of the backplates which turn eccentric cam type adjusters on the inside of the backplate which bear on the brake shoes. The procedure is the same for both front and back drum brakes. The adjusters will be tight and it is important to try to avoid 'rounding' the hexagons. Where possible use a 14mm socket or ring spanner but on front drums the access is restricted and you may have to use an open ended spanner. (We have occasionallly come across adjusters larger than 14mm, probably the result of repairing 'rounded' 14mm adjusters by welding larger nuts on to the damaged adjuster.)
To adjust the rear brakes you will need to jack up the wheel on which you are working so that you can tell when the linings are touching the drums. On front drum brakes there is often 'play' in the driveshafts so that you can move the drum sufficiently without jacking up the car.
Each brake shoe has a separate adjuster so there are two on each backplate. To take up wear on the linings the adjusters must be turned as follows, viewed from the back of the backplate: on the right hand backplates the adjuster nearest the front of the car is turned anti-clockwise and the adjuster nearest the back of the car is turned clockwise. On the left hand backplates the opposite is the case. Turn the adjuster until you can feel the drum is locked by the shoe then turn the adjuster back until the drum turns with the brake shoes just dragging the drum. Repeat the procedure on all eight adjusters.
After adjustment, check the fluid level in the reservoir and top up, with the correct type of fluid, if necessary. If pedal travel is still excessive the most likely cause is a fluid leak or air in the system which should be dealt with urgently.
2 Drum Handbrake Adjustment (refer to illustration and photo below)
Adjustment of the drum handbrake is by way of two wing-nut adjusters on the base of the handbrake lever assembly, below the rear of the gearbox. Adjustment is made with the handbrake OFF.
There is often enough 'play' on the driveshafts to move the drums slightly to ascertain correct adjustment without jacking up the car but if this is not the case raise the front of the car. Turn the wing-nut adjusters clockwise to pull the cable through the handbrake lever and periodically check that the drum still moves. When you feel that the drum is starting to bind, back off the wing-nut. With the handbrake lever pulled out three notches the drum should just be binding and after five notches it should be locked. Repeat this for the opposite side.
(refer to illustrations below) Correct adjustment to front or rear drums can only be achieved if the shoes have been correctly centralised when first fitted. This is done by means of eccentrics on which the lower end of the brake shoes pivot. This involves removing the brake drums. On rear drums this will necessitate a 44mm socket and a long bar as the nut is tightened to a very high torque of at least 250ft.lb. To remove front drums the driveshafts must be removed from the drums (six 14mm bolts) which is made much easier if the front wings are removed. To centralise the shoes correctly a special tool is required but you can make a simple tool from a piece of strong but flexible wire. On the front this is bolted to one of the holes in the drive flange using one of the driveshaft bolts. On the rear the tool or wire is located on the stub axle and the tool itself rotates.
Rear drum >>
THE WESSEX DUCKS
THE WESSEX DUCKS
Turn the adjuster cams so that the brake shoes are just dragging the drum. Remove the drum and fit the centralising tool or the length of wire. The pointer of the tool or the piece of wire bent over at the end should be aligned with the top outer edge of the brake shoe linings. Turn the drive flange with tool attached (front) or tool itself (rear) and check that the tool is just touching the face of both brake shoe linings throughout a complete revolution of the hub. Adjustment is carried out by turning the eccentrics on which the shoes pivot. The eccentrics are kept in the correct position by locknuts. On the front the locknuts are castellated with a split pin to prevent them from turning. On the rear the locknuts are secured by a lock tab which also retains the 'U' spring. If adjustment is necessary, loosen the locknuts, adjust the cams and re-tighten the locknuts (without moving the eccentrics) and replace the split pins or lock tab. After refitting the drums you must adjust the brakes as described above.
The handbrake needs adjusting if you can pull the handle more than six notches on the ratchet before the wheels are locked. Before adjusting the handbrake you should adjust the brakes as described above as this may be enough to correct the handbrake adjustment. If not, proceed as follows.
1 Disc handbrake adjustment (refer to the illustration, right)
Adjustment to the handbrake on front disc brake models is carried out by turning the eccentric adjusters to the correct setting. Correct adjustment can only be achieved if your pads and discs are in good condition. Adjustment is made with the handbrake OFF.
Firstly remove the heater tubes to gain access to the brake calipers. Now undo the eccentrics locking screws and loosen the nuts on the cable end. Raise the front of the car to carry out the adjustments. Set the eccentrics to give the brake pads maximum clearance from the brake disc. Make sure that the levers are touching the stops on the brake caliper housing. Now turn the eccentrics so that the brake pads are just touching the brake disc. Turn the disc to check for any tight spots and re-adjust as required. Re-tighten the eccentrics locking screws making sure the eccentrics donít turn whilst doing so. Check the handbrake lever operation - the pads should start to move on the third click on the handbrake lever and be fully applied on the fifth click on the handbrake lever. Adjust the cable end nut to obtain these settings.
When the cable has been adjusted correctly re-tighten the adjuster nut locking nut. Operate the handbrake lever on and off a few times and then apply the handbrake and check its operation. If the handbrake is ok, lower the car back to the ground and refit the heater tubes. If the handbrake is inefficient follow the guide above again until correct.
<< Front drum
CENTRALISING THE SHOES ON FRONT AND REAR DRUMS