ABS components maintenance

7 -	ABS components maintenance

Adjusting of the AIR-GAP phonic wheel sensor

(For front as well as rear sensor) In each case of maintenance that foresees:

-	replacement or refitting of the wheel

-	replacement or refitting of the phonic wheel (1) or (2)

-	replacement or refitting of the brake discs

-	replacement or refitting of the speed sensor (3) or (4)

-	(front) replacement or refitting of the sensor holder bracket

-	(rear) replacement or refitting of the calliper holder bracket

it is necessary to check the air-gap between the speed sensor and the phonic wheel, once the components are refitted.

For this purpose, use a feeler gauge to check the air-gap; then, carry out 4 measures of the air-gap, one every 90° of wheel turn.

If the difference between the minimum and maximum values detected is higher than 0.40 mm, replace the phonic wheel.

Once checked that the difference is lower than or equal to 0.40 mm, carry out the shimming of the phonic wheel sensor (2) or (5) by the appropriate calibrated thickness spacers (B).

Phonic wheels cleaning

It is important to check that both phonic wheels (21) and (20) are always clean.

Otherwise: gently remove any possible dirt deposits with a cloth or metal brush. Avoid using solvents, abrasives and air or water jets directly on the phonic wheel (21) or (20).

Bleeding of the ABS hydraulic system

If some “sponginess” is detected on the brake control, due to air bubbles in the system, bleed the system, as indicated in Sect. 4 - 3, Changing the brake fluid.

Before bleeding a brake pump, move back the calliper pistons, as indicated in (Sect. 4 - 3, Filling the brake system with fluid) to drain in the pump the air collected near the ABS control unit.

Purge must be carried out by means of the corresponding joints (A) placed near the callipers and the brake pumps.

Do not undo the fixing screws of the joints of the pipes on the ABS hydraulic control unit, unless control unit replacement is necessary.

If the ABS control unit is replaced, this must be supplied with secondary circuit already full of fluid; the control unit must be fitted and the system filled and bleeded as a traditional system.