Disc Designs : General Features

What makes Powerbrake™ discs the best in their class? The following features can be found in every disc that leaves the Powerbrake™ factory. Compare these features with any competitive product and you will see that fanatical attention to detail is what sets Powerbrake™ discs apart from the competition.   

                    
During the disc casting process molten iron is poured into sand moulds at temperatures in excess of 1350°C and allowed to cool rapidly into solid form. This rapid cooling causes internal stresses to be ‘stored’ within the disc casting. Gradual and moderate thermal cycling (such as would be experienced when bedding-in discs properly after fitment) can effectively relieve these stresses but sudden, dramatic temperature changes can lead to distortion or cracking of the disc.

In years gone by it was not uncommon for the manufacturers of high-end engine blocks, brake discs and other cast parts to leave rough castings out in the open for long periods prior to final machining. The gradual heating of the castings by the sun during the day and inevitable cooling at night was believed to be an effective means of stress relieving the castings. Of course in today’s high-volume production environment the time consuming ‘weathering’ of castings is absolutely out of the question. The fact is that practically NO manufacturers (of standard brake discs) make any attempt to stress relieve their castings in any way whatsoever. It is simply considered too time consuming and expensive.

At Powerbrake™ we have spent an enormous amount of time developing innovative methods of ‘weathering’ our disc castings in order to provide our customers with extremely stable disc platform. Our proprietary ‘weathering’ processes increase the disc’s resistance to distortion & cracking as well as substantially improving disc wear life. While we are not going to tell you exactly how we ‘weather’ our castings we are proud to say that laboratory and on vehicle testing have convincingly proven that the substantial time and cost involved in ‘weathering’ each and every Powerbrake™ casting is definitely worth the effort!   

Most disc manufacturers use a single grade of cast iron in the production of their entire range of brake discs. Of course the brake systems on different vehicles differ substantially with regards to design - resulting in differing noise, vibration and braking properties. Powerbrake™ discs are cast from a range of proprietary cast iron alloys that are matched to the vehicle application. This allows us to tailor the friction characteristics and noise damping properties of our discs to the vehicle in question, resulting in optimum brake performance.    

At a typical weight of 5-8 kg’s the brake discs are typically the heaviest rotating components, aside from the wheels and tires, on your car. They also constitute ‘unsprung’ mass. In other words they are attached to the vehicle below the suspension. It is therefore important that they be correctly balanced in order to avoid vibrations that, apart from being frustrating, can interfere with suspension function, traction and handling as well. All Powerbrake™ discs are dynamically mill-balanced. During the process each disc is rotated and any imbalance measured. A carefully calculated amount of material is then milled from the correct location on the outside diameter of the disc in order ensure perfect balance.    

Our MTR system consists of three different colours of thermally sensitive paint that are applied to the outside diameter of all Powerbrake™ discs. Each of the paints change colour at a very specific temperature, providing a permanent record of the maximum temperature reached by the disc. MTR is an extremely useful diagnostic tool for determining whether a brake disc is operating within an acceptable heat range or being run too hot, in which case disc life will be shortened. The MTR system can also be very valuable in determining the correct pad compound to run for a particular driving style. The thermal paint used in Powerbrake’s MTR system is expensive and is therefore used by only a handful of other manufacturers, and then only on their track and race discs. At Powerbrake™ we want our customers to be well informed and gain as much feedback as possible regarding our product and their brake systems in general. As a result EVERY Powerbrake™ disc features our MTR diagnostic system.

MTR colour change guide:
 

Most disc manufacturers stamp a minimum thickness value into the outside diameter of their discs. The hassle here is that it’s difficult to assess whether the disc is reaching its minimum thickness without removing the wheel and measuring the disc thickness using a micrometer. While we are all for accurately measuring disc thickness in this way, we felt that our customers would benefit from being able to perform a quick visual inspection without removing their wheels.

Powerbrake™ discs feature two parallel lines (approximately 2mm wide and 10mm long) that are machined into the outboard friction surface of the disc. These lines are normally visible by looking directly through the wheel spokes, particularly on today’s common alloy wheels. The line closest to the outside diameter is machined to precisely 0.2mm shallow of the disc’s minimum thickness. The line closest to the inside diameter is machined to the minimum thickness. Inspecting disc wear couldn’t get any simpler. When you can see only one line it’s time to book your car in to have the disc replaced. When both of the ‘Wear Watch’ lines disappear your disc has reached minimum thickness and needs replacing. Convenient, simple and safe!   

100% Pre-delivery Measuring of all critical dimensions

At Powerbrake™ we machine our discs to tolerances up to 3 times tighter than the industry norm. Then we carefully measure all critical dimensions on EVERY SINGLE disc that leaves the factory prior to packaging and shipment. Measuring is performed using equipment capable of measuring accurately in increments of 0.005mm (5 microns). We will NEVER ship a disc that has unacceptable run-out or disc thickness variation (DTV) values - period! This 100% measurement policy is extremely rare among disc manufacturers today. Most manufacturers settle for batch testing, which involves the measurement of a certain number of discs from each production batch. That simply doesn’t cut it at Powerbrake™. When you fit a Powerbrake™ disc to your car you do so knowing that it is running perfectly true. We can say this with confidence because it was precisely measured prior to shipping. If it was not perfect, it would never have left the factory! (To learn more about the impact of run-out and DTV measurements click here)   

Dry Coatings

All Powerbrake discs are plated with a unique 'dry' protective coating. As a result our discs need no further cleaning or preparation prior to fitment. The brake pads will cut through the dry coating, in the pad-track area, during the first few brake applications. The silver coating can withstand 650 deg C and will provide increased corrosion resistance on the non-swept areas of the disc, keeping your discs looking good behind open wheels. The real reason for the coating, however, is not corrosion resistance but rather the fact that we do not want any form of oil coating on our discs that may negatively effect friction levels and brake performance. Most aftermarket discs are packaged with an oil coating to prevent rust during transport and storage. Very few fitment centres properly remove this coating and as a result there is a film of oil left on the discs when fitted. This oil film contaminates the brake pads, acts as a lubricant and can substantially reduce brake performance.