GT & LMP Brake Carbon User Guide

GT & LMP Brake Carbon User Guide

- H14 Pads New 31.5mm - Pads are allowed to wear down to 12mm which give 19.5mm of wear x 2 = 39.0mm.

- H17 Pad New 27.0mm - Pads are allowed to wear down to 12mm which give 15.0mm of wear x 2 = 30.0mm.

- H17i Discs New 37mm - Allowed to wear to 25mm which gives 12mm wear.

- H13.5 Discs New 35mm - Allowed to wear to 25mm which gives 10mm wear.

LMP 675
Pads New 25mm - Pads are allowed to wear down to 9mm which gives 16mm of wear x 2 = 32mm.

- Discs New 35mm - Discs are allowed to wear to 25mm which gives 10mm wear.

Bedding Discs And Pads Prior To Race

Because of its lower operating temperatures, compared to other carbon brake materials, it is easy to achieve running temperatures without the problem of glazing the rubbing faces. Blanking the brake ducts is not required in dry conditions. The driver should apply hard brake pressure, in short applications, taking care not to drag the brakes under lighter loads. This may result in glazing. If this occurs and the driver reports there is inadequate retardation, then the pads should be removed from the calipers and both these and the discs should have the rubbing faces deglazed with emery paper, and the carbon dust removed before use.
Cooling Requirements
The uprights should be designed to provide a cooling air pathway of at least 140cm² area. AP Racing carbon/carbon requires good face cooling. It is worth monitoring airflow / temperature on both inside and outside disc faces during testing. It may be found that a larger face-cooling gap is required for the inside face to equalize the face temperatures. This is due to the tendency of the airflow to bypass this outlet when exiting the upright and flowing to mainly up the outside face. The resultant temperature differential can lead to uneven wear, especially if temperature / wear is high.
Monitoring Temperatures
The most reliable way of monitoring the disc temperature is by the application of temperature indicating paints. Use of pit lane thermocouple temperatures is useful for achieving a front / rear balance.
The green (430°C) and red (610°C) paints are usually used. It is not advisable to use the orange (560°C) paint, as this will promote local material oxidation.
The brown antioxidant paint on H13.5 and H14 and clear coating on H17 and H18 carbon must be completely removed from a section of the disc O.D. before the paints are applied. Failure to do this could result in the indicating paint not changing colour, regardless of the operating temperature.

The temperature paint colour change is not instantaneous, but is accelerated by higher temperature and the time at temperature is cumulative. It is therefore advisable that at least 5 consecutive laps at representative speed are completed before reference to the temperature paint. Turning the green paint (white) across 75% of the disc width is adequate. Turning the red paint (white) just on the disc edges (2-3mm) is acceptable. Running the material at higher temperatures will only result in increased wear rate. If the red paint has changed to white across the entire disc width, extra cooling must be applied. Continued running at this level of temperature may result in excessively high wear rates, and can lead to weakening of the disc structure.

Temperature Converter °C to °F - Enter a number and click on the "Convert" button

°C   =   °F


If the disc and pad surfaces are worn unevenly they can be machined flat and parallel again, AP Racing can provide this reconditioning service. Brown antioxidant paint for H13.5 and H14 Carbon is available from AP Racing (CP2872-145) and should be “touched-up” as required. Do not attempt to degrease the material with any solvents. Most contaminates can be evaporated by heating in an oven for half hour at 300°C.
Disc Condition
Experience has shown that if normal operating guidelines are adhered to, AP Racing carbon discs can safely be used down to their minimum thickness.
However, if for any reason discs are used at very high temperatures it is possible for oxidation to occur throughout the material. This will severely weaken the carbon structure, therefore avoid running the disc with the red paint fully turned to white across the whole width of the disc.
AP Racing Carbon Part Numbers
GT Discs Pads Stack Height
CP2872-334:GT 380 x 35mm CP4970-30H14 31.5mm 98mm
CP2872-355H13.5 355 x 35mm CP4970-30H14 31.5mm 98mm
CP2872-400 / -401H17i 380 x 37mm CP4970-28H18 27mm 91mm
CP2872-402 / -403H17i 355 x 37mm CP4970-28H18 27mm 91mm
LMP 675 Discs Pads Stack Height
CP2872-355H13.5 355 x 35mm CP4240-54H14 25mm 85mm

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