Modifications – Brake Rotors & Pads

Cross Drilled and Slotted Rotor

This first part of the modifications series addresses the brake rotors and pads that improve stopping power. All too often we hear of pals going for brake upgrades due to a close shave, or something they’ve done on their last car and liked or simply just for the looks of things.

All in all, upgrading to a set of matching/compatible brake rotors and pads should not be much of a bank breaker (pun not intended) nor put a stop (yes, intended) to your luxuries budget for the quarter.

Brake Rotors

Brake Rotors spin in circles and take repeated beatings. Repeated hard stops require both effective heat transfer and adequate thermal storage capacity within the disc. The more disc surface area per unit mass and the greater and more efficient the mass flow of air over and through the disc, the faster the heat will be dissipated and the more efficient the entire system will be. At the same time, the brake discs must have enough thermal storage capacity to prevent distortion and/or cracking from thermal stress until the heat can be dissipated. This is not particularly important in a single stop but it is crucial in the case of repeated stops from high speed.

Drilled Rotors

Drilled Racing rotors have always been the requirement for many years. It is still now a popular choice for many of the uninitiated in the world of brakes. But there were two good reasons why it was needed:

  1. The holes allowed the boundary layer of gasses and particulate matter a place to go,
  2. The edges of the holes also gave the brake pads a better bite

We remember the last time a drilled rotor rocked up; It sure looked like there were cracks at the edges of the holes. The stress marks significantly decreased disc life. Thankfully since then, major improvements in material choices have removed the need for the drilled rotor. Racing rotors now run channels or tangential slots that serve the same purpose without the disadvantages.

Slotted Rotors

Slotted rotors are a solution touted to prevent glazing but we don’t have any conclusive data on that. Regardless, thankfully this new design doesn’t weaken the rotor as much as a drilled rotor.  Compared to the small holes of a cross-drilled rotor, the slotted rotors give your pads a tough life. As such, slotted rotors offer improved bite and a higher friction level as opposed to the blank rotors available from the factory.

As a disadvantage, you’ll experience slightly reduced pad life and some tiny vibrations through the pedals when braking hard from high speeds.

That aside, these slotted rotors are a beautiful invention to view while parked. When possible, go for them. Looking good is half the battle won.

Dimpled Rotors

Dimpled rotors are the replacement for drilled rotors. With the need to circumvent the stress cracks from drilled rotors; Manufacturers turned to dimpled rotors. Dimpled rotors offer the initial bite of drilled rotors without the extra ‘luxury’ of stress cracks forming on an otherwise beautiful disc. These are a ‘safer’ option in place of drilled rotors.

We suggest the painting of the dimples to give the drilled look. Just kidding 🙂

Oversized Rotors

Manufacturers have already placed the largest disc they can into your braking system

Brake Pads

Brake pads aren’t really a black art but as all things go; They must be matched to the application. There are many different pad compounds out there, so choosing the right one for yourself is still a task that takes a little bit of confession – Largely, confessing that we don’t need the 800degC Racing pad for driving the kids to school. Other than that, the various compounds available to the public nowadays are categorised into the following:

  • Non-metallic materials – these are made from a combination of various synthetic substances bonded into a composite, principally in the form of cellulose, aramid, PAN, and sintered glass. They are gentle on rotors, but produce a fair amount of dust and have a short service life.
  • Semi-metallic materials – synthetics mixed with some proportion of flaked metals. These are harder than non-metallic pads, and are more fade-resistant and longer lasting, but at the cost of increased wear to the rotor/ drum which then must be replaced sooner. They also require more force than non-metallic pads in order to generate braking torque.
  • Fully metallic materials – these pads are used only in racing vehicles, and are composed of sintered steel without any synthetic additives. They are very long-lasting, but require even more force to slow a vehicle and are extremely wearing on rotors. They also tend to be very loud.
  • Ceramic materials – Composed of clay and porcelain bonded to copper flakes and filaments, these are a good compromise between the durability of the metal pads and the grip and fade resistance of the synthetic variety. Their principal drawback, however, is that unlike the previous three types and despite the presence of the copper (which has a high thermal conductivity), ceramic pads generally do not dissipate heat well, which can eventually cause the pads or other components of the braking system to warp.[2]However, because the ceramic materials causes the braking sound to be elevated beyond that of human hearing, they are exceptionally quiet.

credited to Wikipedia (http://en.wikipedia.org/wiki/Brake_pad)

Temperature

Brake pad temperatures can vary depending on the type of compound and application. As said before, we won’t be needing a 800degC metallic pad to send the kids to school. That’s the maximum temperature as advertised but do keep a lookout for the temperature at which the brake pads begin their work. If the starting temperature rating is too high, that means the brakes will not be working terribly well when you take a stab at the brakes for the first time during that cold rainy day. Pads, as much as their touted to be, do check that your street pads begin working from cold to avoid disappointment.

Any typical normal driving temperature for the rotors will range between 100-200 degC on application. When daddy said not to touch them rotors, it was a good idea to listen. Anything above that is subject to usage. Track usage typically sits a smidgen under 800degC. Extrapolating from that, we can safely guess that most Sporty Street Cars can get by with 400-500degC pads.

 Summary

Ultimately, as big as brakes go or as hard as they may stop you. Tyres are the only contact point between your car and the road. Matching your braking capabilities to the requirements is most times the best approach.