Brake Pads Prepare to win By Vic Eacott of FRIXA High Performance Brakes
Brakes are arguably the most important component on your kart, but how much do racers really know about the preparation of the system for both speed and safety?
ou have two very small brake pads and a small brake disc which, in essence when both are in operation, produce more than 300°C of heat, also not forgetting the specialised brake ﬂuid that works with these specially designed components working at high temperatures. In the last eight months, I have been given a project by my company, FRIXA, who are brake manufacturers, and I am a brake development specialist myself in designing improved brake pad materials. When brake pads are manufactured, the material in its rough and simple state is simply dust, mixed with certain properties and specialised resins that bond all the materials together. Each pad back plate, (what the pad material is ﬁxed to) is then placed in a mould, where the ‘dust’ is pressed under extreme pressures into the shape and proﬁle of the back-plate, ending up as a ﬁnished brake pad. A set of new brake pads have to be
Material destroyed from failure to bed in, resins inside the pad have separated and boiled under extreme abuse and heat bedded in. This cannot be done with a kart sitting on a stand with a person ‘manually’ bedding in the brake pads, it has to be done whilst the kart is moving on the circuit and a thorough and precise process is involved in completing the bedding in procedure - this is of paramount importance and a safety issue.
The Bedding In Process After you have had new brake pads ﬁtted, or a new disc, or both, don’t drive at full speed onto the circuit with new pads and force the brake pedal until you can feel the brakes working.
Various samples showing bedding in has not been carried out and the driver has been resting their foot on the brake pedal causing overheating and abnormal pad wear
Reasons for bedding in brake components The main reason for bedding in the brake disc and brake pads is ﬁrstly to deposit an even layer of friction material on to the surface of a new disc, from the brake pad materials, and the newly ﬁtted disc has to be thermally conditioned too, as well as the brake pad materials. Taking the brake pad material through the pre-heat cycle with the brake disc is also of vital importance and accounts for imperfections in the newly- made brake pads, these can be removed and the pad surface can be correctly proﬁled with the brake disc. The two newly manufactured products (brake pads and disc) are made by two types of specialised manufacturing; therefore these products are not made as buddy pairs. Bedding in will not only prolong the life of each of the products but also allow the best performance and conﬁdence using these products under race conditions. Failure to provide the correct bedding in processes of these components will have potential consequences occurring during the use of the products.
Understanding Metal: Heat and Friction All metals that have been manufactured to accommodate friction have a thermal threshold, friction level and a ‘safe’ 20 Karting magazine August 2011
Bedding in new brake pads with new or used discs 1. When you install a brake pad set into the caliper, make sure your hands are free of grease or other contaminates that could aﬀect the material of the brake pad. You can buy surgical type gloves which will prevent any foreign material contaminating the pad material on installation.
2. Make sure you clean all the old contaminates oﬀ the brake disc too, with prime brake cleaner ﬂuid, and afterwards with a medium heavy abrasive cloth, to remove any remaining old pad materials that have been embedded into the brake disc metal, and then clean the disc oﬀ again using the brake cleaner to remove any abrasives from the cloth that will damage the new brake pad materials if left uncleaned. Do not use abrasive materials on the disc face to try to obtain more grip from the brake pads under braking, it will not change in any way the brake operation or improve the kart’s braking capacity. If you think it does, you are probably using the wrong type of brake pads for your driver’s style or race conditions, so try a diﬀerent type of brake compound. 3. It is boring, but you need to give up your ﬁrst test session. You could bed in several sets of pads and make sure you mark each pad set and for which side of the caliper they came from. Don’t cut corners in this process, it’s not only expensive to keep buying new pads, it is bad practice to race Thermal conditioned and correctly bedded in
with unprepared products. After correctly ﬁtting the brake components and, bleeding the hydraulic system correctly, cover the caliper intake with duct tape or any suitable covering to conserve the heat cycle process. Do not use abrasives on any of the brake pad material at any time. 4. Go out onto the track and make ﬁve light stops from a slow speed and with very light pedal pressure to complete the brake system check. Check to feel if the brake pedal is in operation and that there is no loss of brake ﬂuid pressure. 5. Increase the speed to up to 50% of your maximum revs then release the accelerator pedal, allowing the kart to slow, then with a light pedal pressure, operate the brake pedal until you feel a very slight resistance, applying this pressure for just 3s – release the brake pedal and repeat this 12 times and ensure you are at 50% revs and no more. 6. Further increase the speed of the kart to 75% of your maximum revs then release the accelerator pedal. Again, allow the kart to slow, then again, with moderate pedal pressure, operate the brake pedal until you feel more resistance and hold the brake pedal for 5s. Repeat this 15 times and make sure you are not above 75% revs throughout this process. Do not at any time force the brake pad to make the kart slow down - when you are bedding in brake pads you won’t feel the brakes working adequately until they are bedded in. Don’t keep your brake foot on the pedal at the same time as you accelerate, these are two separate actions. 7. After this bedding in process go back to the pits and remove the duct tape then allow the pads to cool. It may help to remove the pads from the caliper but ensure you have marked each pad on its removal so it is replaced back in the same side of the caliper. This will not only save you money but increase the performance of your brake eﬃciency by 70% and you will ﬁnd your brake pads will last longer too.
operating temperature. When any of these tolerances have been exceeded, the metal will become soft, disﬁgure, deteriorate or simply disintegrate and the pad materials will break down. Metal discs are manufactured and machined to ﬁt all types of karts and we have experienced that discs can suﬀer from premature cracking and ageing. Expansion and contraction (friction use) inducing heat into the metal can increase and decrease the disc size and shape. The thermal conductivity is being induced into the metal via brake pad operations by the bedding in process, so if this is ignored it could lead to life threatening consequences.
FRIXA are gaining rapid acceptance in the karting industry, with reputable dealers such as Ogden Motorsport and KKC stocking the pads. OTK pads are available already and are successfully used by drivers like John Stewart in Rotax Super One, and pads for the CRG-made karts (CRG, Maranello, Zanardi and LH) will be available by the end of July. For more information see www.frixa.org or follow @brakeguru on Twitter. August 2011 Karting magazine 21