Notes on evaluating brake disks - AH42.10-P-9406-07GBB

MODEL 199 with CODE U28(19-inch brake system) 

AH42.10-P-9406-07GBB	Notes on evaluating brake disks
	Clean brake disks	Model 199 with code (U28) 19 inch brake system	AP42.10-P-4258-01A

GENERAL 

Wear: 

Always check both sides of brake disk for signs of wear.

Otherwise higher wear through higher thermal load on INSIDE  of brake disk may be overseen.

Signs of wear on the front or rear brake disk are:

• Friction path chipped or shows signs of oxidation on the friction track
• "Erosion" on edge of brake disk
• Crack formation across the friction track

Always replace both  brake disks on an axle.

The cause of any different degree of wear between two brake disks on an axle must be determined and eliminated.

GENERAL 

Handling: 

Always handle brake disks with great care. They may only be transported in suitable containers.

Blocking of the wheel hub by using pliers, levers or screwdrivers at the brake disk as well as removal of the brake disk using a hammer is not permissible.

The resultant breaks and cracks lead to destruction of the brake disk.

Fig 1: Identifying Brake Disk With Thermal Stress Crack

Courtesy of MERCEDES-BENZ USA

GENERAL 

Crack formation: 

Always replace brake disk with thermal stress crack (arrows).

The mechanical load is highest in the connection area. Thermal stress cracks (arrows) frequently occur here first.

FRONT AXLE 

Friction track wear: 

The degree of wear can only be established by weighing  the brake disk.

Clean brake disk before weighing.

Enter values determined in May SIS [Maybach SLR Information System].

• Clean: 

Do not use any drills or machines.

The slightest removal of material leads to destruction of the brake disk.

Clean bores of friction surface using steel pin (Ø = 3 mm) and then remove waste with vacuum cleaner.

For cleaning use corresponding special tool only.

For more details on cleaning, see reference in record title table.

• Weighing: 

The weight must be 20 g over  the minimum weight.

The minimum weight is specified on the brake disk.

FRONT AXLE 

Wear profile of friction track: 

Brake disk, new (e.g. after brake break-in procedure).

Fig 2: Identifying Brake Disk

Courtesy of MERCEDES-BENZ USA

FRONT AXLE 

Wear profile of friction track: 

Brake disk, used (e.g. after 500 to 1000 km on race track).

External features: isolated signs of oxidation, matt friction track; also dirty, greasy friction track

Immediate measures required:

• Remove  brake disk.
• Clean  brake disk.
• Weigh  brake disk.
  Fig 3: Identifying Brake Disk

  Courtesy of MERCEDES-BENZ USA

FRONT AXLE 

Wear profile of friction track: 

Brake disk heavily loaded (e.g. after 2000 km on race track).

External features: closely packed signs of oxidation, deep breakouts; also glazed friction track.

Immediate measures required:

• Remove  brake disk.
• Clean  brake disk.
• Weigh  brake disk.
  Fig 4: Identifying Brake Disk

  Courtesy of MERCEDES-BENZ USA
  Fig 5: Identifying Brake Disk Edge Length

  Courtesy of MERCEDES-BENZ USA

REAR AXLE 

Friction track wear: 

Friction track chipped to a minor extent. As of an edge length (a) of 19 mm the brake disk should be replaced.

The cause is thermal stresses on the friction layer (2). Up to an edge length (a) of 19 mm these chips on the friction track are inconsequential.

Fig 6: Identifying Brake Disk Outer Edge Thickness

Courtesy of MERCEDES-BENZ USA

REAR AXLE 

Wear on edge of brake disk: 

The thickness of the outer edge (1) of the brake disk reduces more quickly than the friction layer (2).

Due to oxidation processes the carbon fibers form ash and the basic material at the outer edge (1) of the brake disk gets "like charcoal".

The erosion at the outer edge (1) of the brake disk is invisible due to lining material which is smeared on.

Replace  brake disk, if:

• The friction layer (2) in the area (A) has broken out  by more than 10 mm x 1 mm

or

• the friction layer (2) has sub-surface corrosion due to oxidation  of the basic material.

The minimum permissible thickness of the REAR AXLE BRAKE DISK  is 24 mm at the outer edge (1), see dimension (b).