Alcon HD Brake Servicing and Maintenance

Servicing and maintenance instructions

• Pads should be examined regularly for wear and condition. Replace pads when less than 2mm of friction material remains anywhere over the surface.
• When fitting new pads, thoroughly clean the pad location faces in the caliper, removing any debris and brake dust with brake cleaner and a stiff brush.
• The protruding pistons must be wiped clean before they are pushed back into the bores. 
• Discs must be replaced when the total thickness has worn below the minimum indicated on the disc or when any of the face grooves across either inner or outer face have worn away.  Generally this is about 3mm total disc thickness.
• If a disc shows any sign of cracking, which may occur after heavy usage, it must be replaced.
• Remember to bed-in new pads and discs as described on the previous page.

Alcon Seal replacement - See replacement Alcon Seals Here.

As brake calipers are a safety critical part of the braking system, Alcon recommends that they are inspected and serviced regularly to ensure consistent performance. The main service item within the caliper assembly is the caliper pressure seal, although the pistons and their coating should also be inspected during a service.

Stage 1 – Soak Seals
Soak new caliper pressure seals in the mineral oil hydraulic fluid for a minimum of 60 minutes prior to build.

Stage 2 – Exterior Clean
The exterior of the brake caliper should be clean before attempting the removal of the caliper pistons. The exterior can be cleaned using warm soapy water, and the caliper should be dried off prior to disassembly. Performing an exterior clean will reduce the risk of dirt and other contaminants entering the hydraulic system.

It is acceptable to omit this process if a post strip down wash of all components is going to be performed prior to rebuild.

Stage 3 – Piston Removal - See AlconKits brake tools here.

To ease removal of the caliper pistons, a self-centring block can be used. Alcon ecommend using a suitably sized block, 26mm thick, between the pistons which centres itself within the caliper using the disc pathway (see image below).

You can find piston removal wrenches here: Alconkits Piston removal tools

With the block inserted, the caliper pistons can be moved forward under pressure (hydraulic or air). Hands and other body parts must be kept well clear of the caliper pistons to avoid injury. In the case of using air pressure to drive the pistons forward, hands and other body parts should be kept away from escaping air.

Once pistons are protruding from the caliper bores, remove the pistons from the caliper 

Stage 4 - Seal removal
Carefully remove old pressure seals and wiper seals from their grooves using a thin, blunt edged tool to remove the seal from the groove.

Stage 5 – Internal Clean
The caliper bores, seal grooves and pistons should all be cleaned prior to re-assembly. Alcohol based cleaning agents may be used. Ensure that bores, seal grooves and pistons are completely clean and free from contamination and moisture. Care should be taken when cleaning the caliper pistons so that no damage is caused to the piston coating. If the
piston coating appears to be excessively worn, then the pistons should be replaced with new or reconditioned pistons.

Stage 6 – Rebuild
Fit replacement caliper pressure seals and wiper seals into grooves ensuring that they are correctly seated. Seals should sit smoothly in the grooves and have no kinks or twists visible.

The wiper seal have a ‘v’ section and is fitted to the outer seal groove.

Apply a small amount of brake fluid to the corner radius of the piston at the base, as this will help with re-assembly. Carefully engage the piston in its bore and apply even
pressure to guide it through the pressure seal. Once fully engaged with the seal, the piston should be pushed to the bottom of its bore.

DO NOT USE EXCESSIVE FORCE TO INSERT THE PISTON THROUGH THE PRESSURE SEAL. If piston does not slide through the seal, remove the piston and check seal is correctly seated, re-apply lubrication (brake fluid) to both the seal and piston corner radius and re-insert.

Where possible, calipers should be pressure tested prior to use on the vehicle.

Routine Servicing of Alcon Calipers

Vehicle braking system servicing must always be carried out strictly in accordance with the vehicle manufacturers instructions.

In order that vehicle braking systems remain in good working order and provide the essential safety and reliability, periodic checks and replacement of certain components is necessary.

Alcon caliper Pads - See here.

Alcon replacement rotors - see here.

Every month or 1,000 miles ( 1,500 km )

• Check fluid levels in reservoirs and top up if necessary with DOT5.1 brake fluid
  Every 6 months or 6,000 miles ( 10,000 km )
• Check the brake pads for wear. Replace pads when less than 2mm of friction material remains anywhere over the surface.
• Check the brake discs for wear and damage. Discs must be replaced before the total thickness has worn below about 3mm or when the disc gas slots are no longer visible. This figure is marked on the outside rim of the disc. If a disc shows any sign of cracking, which may occur after heavy usage, it must be replaced.

Every 18 months or 18,500 miles ( 30,000 km )

• Completely drain the braking system and renew the hydraulic fluid (this period may be more frequent in high humidity territories).
• Remove brake pads and check their condition particularly between the friction material and metal backing plate. If this is present, renew pads regardless of their state of wear.
• Visually examine all hydraulic units for signs of fluid leakage. Replace or overhaul if necessary.

Every 3 years or 93,000 miles ( 150,000 km )

• All hydraulic assemblies should be replaced or overhauled.