AP Racing Catalogue Issue 4

45 visit www.apracing.com for installation drawings & up to date product range details BRAKE DISCS - Carbon / Carbon - General Information INTRODUCTION Carbon/Carbon brake discs & pads offer very lightweight construction together with excellent braking performance. Carbon/Carbon is also expensive but if managed correctly, mainly a question of temperature control, then wear rates and hence running costs can be surprisingly low. AP Racing has more than 30 years of experience with Carbon/Carbon brakes in F1 and Sportscar racing and we recommend and supply a number of Hitco Carbon/Carbon materials which we consider to offer the best performance and braking characteristics together with low wear of any material currently available. This section on Carbon discs is designed as a users guide for reference only and we recommend you contact AP Racing technical department for more detailed information before finalising installation details. BEDDING DISC AND PADS PRIOR TO RACE Because AP Racing Carbon/Carbon brake materials have lower operat- ing 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. When bedding the driver should apply hard brake pressure in short applications. Take care not to drag the brakes under lighter loads as thismay 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 de-glazed with coarse emery paper and dust thoroughly removed. COOLING REQUIREMENTS The uprights should be designed to provide a cooling air pathway of at least 140cm 2 area. Hitco 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 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 indicating paints. Use of pit lane thermocouple temperatures is useful for achieving a front / rear balance. The green (430 o C) and red (610 o C) paints must only be used. It is not advisable to use the orange (560°C) paint, as this will promote local material oxidation The 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 75% across disc width is adequate. Turning the red paint 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 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. WEAR PREDICTION If high brake wear is anticipated in the race, it is important to complete as many laps as possible in “race trim” (using a measured set of carbon) during practice. A race wear prediction can then be made using a similar system to that detailed on the AP Racing “Carbon Brake Life Evaluation” sheet which can be obtained fromAP Racing or from our website. All laps (including “in” and “out” laps) are included and a 1.5 x safety factor applied. MAINTENANCE If the discs and pad surfaces are worn unevenly they can be machined flat and parallel again. A fixture should be made to mount the disc on its mounting flange, and both sides should be machined at the same setting. Failure to do this may result in thick / thin which will cause pedal “pulsing” and vibration. NOTE: Do not attempt to degrease the material with any solvents. If a Carbon disc is contaminated with oil or other please contact AP Racing for advice DISC CONDITION Experience has shown that if normal operating guidelines are adhered to, Hitco Carbon/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 blown. WEAR GUIDE AP Racing carbon discs have disc wear indictors in the brake face and vary depending on the new thickness. - 37mm Thick discs which have angles vents have a 16mm diameter indicator 1mm deep a 12mm diameter indicator 3.5mm deep, and there is a triangle wear indicator that is 6mm deep. This indicator shows the direction of rotation of the disc and is the last wear indicator. All these indicators are on both sides of the disc. These are there to give the user a guide as to the disc wear and when the triangle indictors are no longer showing the disc is at or below 25mm its minimum thickness. - 35mm Thick discs that use angles vents have a 12mm indicator 2.5mm deep and there is a triangle wear indicator that is 5mm deep. This indicator shows the direction of rotation of the disc and is the last wear indicator. All these indicators are on both sides of the disc. These are there to give the user a guide as to the disc wear and when the triangle indictors are no longer showing the disc is at or below 25mm its minimum thickness. - 35mm Discs which run non-handed vents have a 12mm diameter indi- cator 2.5mm deep and an 8mm diameter indicator 5mm deep. When the 8mm diameter indicator is no longer visible on both sides this will show the disc is at or below its 25mm minimum thickness. NOTE:- In some circumstances one disc face may wear more than the other. If the disc shows signs of this you must make sure you keep a minimum disc thickness of 5mm between the outer disc braking face and the inner cooling vent hole in the centre of the discs. TECHNICAL CONTACTS AP Racing offer several different Carbon materials for different applications and operating conditions. The choice of the best material for given application is complex. Please contact AP Racing technical department (racetech@apracing.co.uk ) or one of the following engineers directly. Note: See page 46 for Part Numbering. - Peter Harris Key Account / Race Engineer, GT / Touring Car . - Office Tel:+44 (0) 24 7688 3305 - Mobile: +44 (0) 7881 782 561 - E-mail: peter.harris@apracing.co.uk CUSTOMER NOTES RECONDITIONING The Carbon Discs may exhibit uneven surfaces when worn. AP Racing offer a reconditioning service to re-machine disc faces.