08/12/2012
Understanding Brake Fade and Maintenance in Autocross
Much like a skydiver relies on a meticulously designed parachute for a safe descent, a car engaged in the demanding world of autocross requires equally precise and reliable braking components. While all brake pads share the fundamental purpose of creating friction to slow a vehicle, their performance characteristics can vary dramatically, especially when pushed to their limits. This is particularly true in autocross, where a combination of aggressive driving and high-grip tires can place significant demands on your braking system.
The question often arises: are high-performance brake pads a worthwhile investment for autocross? While a typical 60-second autocross run might not generate the extreme temperatures seen in endurance racing, elevated brake temperatures are still a reality, especially with a co-driver or during extended practice sessions. Furthermore, the sticky, aftermarket tires commonly used in autocross can amplify the demands placed upon the braking system. Can an improvement in brake pad performance translate into quicker lap times when paired with these grippier tires?
To investigate this, a 2010 Mazda MX-5 project car was utilised as a testbed. This platform, equipped with KW coil-over suspension and sticky Dunlop Direzza Sport Z1 Star Spec tyres, provided an excellent foundation for evaluating brake pads. The car's predictable nature and the consistent performance of the Dunlop tyres across a range of temperatures made it ideal for objective testing. Data acquisition was handled by a Race Technology DL1 logger, while a Vericom VC2000 measured 60-to-zero stopping distances.
Test Methodology and Preparation
The testing regimen involved four distinct brake pad compounds, each installed on a fresh set of Centric rotors to prevent cross-contamination. The selected pads were:
- OE Mazda Pads: The original equipment fitted to the MX-5.
- Hawk HPS (High Performance Street): A step up for street performance and light track use.
- Hawk HP Plus: Designed for higher heat capability, favouring track and serious autocross use.
- Hawk DTC-60: A race-specific compound engineered for extreme track conditions.
Each set of pads underwent the manufacturer's recommended bedding-in procedure, which typically involves a series of stops from speed followed by a cooldown period. This process is crucial for preparing the pad and rotor surfaces for optimal performance and to ensure the longevity of both components. Following bedding, the pads and rotors were removed and stored separately until the main testing day.
The testing sequence for each pad compound was consistent. It began with four two-lap runs on the test course, designed to simulate autocross conditions. Immediately after these dynamic laps, five 60-to-zero stopping distance tests were conducted on a level asphalt surface. This comprehensive approach allowed for the evaluation of both dynamic handling and static braking performance.
Brake Pad Performance Analysis
Original Equipment Mazda Pads
The OE Mazda pads, featuring a ceramic-based compound, offered a significant improvement over older generations of stock brake pads. They provided a good balance of pedal feel and fade resistance without the common drawbacks of increased noise or dust. However, during testing, drivers noted that their initial bite and overall stopping power felt better suited to the car's original tyres rather than the higher-grip Dunlops. Significant pedal pressure was required for strong deceleration.
Despite this, the OE pads exhibited no major flaws. Drivers reported consistent modulation and pedal feel, even at the limit of braking. There was no noticeable brake fade, and the pads operated smoothly, quietly, and cleanly. The general consensus was that while they required more leg effort, they offered a good, linear feel, directly correlating pedal input to braking response.
| Metric | Value |
|---|---|
| Price (Front & Rear) | $172 |
| 60-to-Zero Distance | 115.7 ft |
| Peak Braking | 1.167g |
| Lap Time | 53.10 sec (Retest: 53.37 sec) |
Hawk HPS (Performance Street/Autocross) Pads
The Hawk HPS pads represented a noticeable step up in performance. Constructed from a carbon-based friction material, they promised increased stopping power with minimal increases in noise and dust, along with a higher heat range suitable for spirited street driving, autocross, and light track use. Both test drivers observed a welcome increase in initial bite and overall stopping power compared to the OE pads.
The HPS pads were praised for inspiring driver confidence, particularly when pushing the car to its performance limits. Their quicker reaction time and stronger braking felt more in sync with the modified MX-5. The strong initial bite and a flat brake torque curve were described as a positive interaction with the tyre's contact patch, allowing drivers to better feel and manage the braking limit. Furthermore, the HPS pads were noted as being less physically demanding on the driver, requiring less effort for maximum performance.
| Metric | Value |
|---|---|
| Price (Front & Rear) | $136 |
| 60-to-Zero Distance | 114.5 ft |
| Peak Braking | 1.175g |
| Lap Time | 53.13 sec |
Hawk HP Plus (Track Day) Pads
The Hawk HP Plus pads, while similar to the HPS in their multi-purpose design, leaned towards higher heat capacity, potentially at the expense of increased noise, rotor wear, and dust. Hawk positions these pads as track-capable while still being suitable for the drive home and for serious street and autocross enthusiasts. Compared to the HPS, the HP Plus delivered a significant increase in initial bite and considerably more stopping power.
This enhanced braking performance led to an interesting observation: drivers found themselves over-slowing for turns, misjudging their braking points due to the pad's aggressive torque ramp-up. The braking force increased noticeably without a corresponding increase in pedal pressure. While this trait initially caused over-braking, drivers found it relatively easy to adapt to. The HP Plus pads instilled confidence due to their reassuring braking effort, which climbed gently even without additional pedal input.
The braking inputs with the HP Plus required a more nuanced touch, becoming a more cerebral exercise than a purely muscular one. The additional power was reassuring but could be slightly abrupt for autocross. Drivers who weren't fully accustomed to the pedal feel might find themselves slowing too much at the end of slaloms or into final turns. However, the ability to modulate brake pressure with the toes and ankle, rather than the entire leg, allowed for very fine-tuning of braking force.
| Metric | Value |
|---|---|
| Price (Front & Rear) | $170 |
| 60-to-Zero Distance | 114.7 ft |
| Peak Braking | 1.162g |
| Lap Time | 53.08 sec |
Hawk DTC-60 (Full-Race) Pads
The Hawk DTC-60 is a dedicated race compound, designed for temperatures between 400 and 1600 degrees Fahrenheit. Below this temperature range, these pads can be harsh on rotors and generate substantial noise and dust. They are engineered to withstand the extreme demands of track racing and are generally not recommended for street use.
Despite its hardcore nature, the DTC-60 performed surprisingly well on the test course. Contrary to expectations for a true race pad, there wasn't a dramatic increase in initial bite as the pads warmed up. They delivered strong response from the initial pedal application and provided ample stopping power, even when cold. However, two notable drawbacks emerged. The initial bite was so aggressive that it could momentarily lock the front tyres before weight transfer occurred, slightly delaying full braking. This also caused the ABS system to work harder, cycling pressure and negatively impacting peak braking g-loads.
Furthermore, the DTC-60 pads lacked the desired feel and feedback through the pedal. The intuitive connection felt with the HPS pads was replaced by a more 'dead' pedal feel, making it difficult for drivers to interpret what was happening at the tyre contact patch. While successive laps allowed drivers to adapt by gently squeezing the pedal rather than abruptly applying it, the lack of immediate feedback remained a concern for optimal control.
| Metric | Value |
|---|---|
| Price (Front & Rear) | $308 |
| 60-to-Zero Distance | 115.3 ft |
| Peak Braking | 1.151g |
| Lap Time | 53.26 sec |
Key Takeaways for Autocross Braking
The data collected revealed an interesting outcome: despite the noticeable differences in feel and initial bite between the brake pads, there were no significant objective differences in lap times, peak stopping forces, or stopping distances. This is largely attributed to the fact that the tyres, a primary factor in overall braking performance, remained constant throughout the test.
However, the subjective experience of the drivers highlighted the importance of pedal feel and consistency. These factors can significantly contribute to driver comfort, which in turn can foster confidence and lead to improved performance. For autocross, selecting brake pads based on their feel and how well they communicate with the driver, rather than solely on theoretical performance metrics, is a sound strategy. The test drivers expressed a strong preference for both the Hawk HPS and HP Plus pads, with the HPS being the recommended choice for future testing due to its balanced performance and excellent feel.
Brake fade, while less of a concern in short autocross runs compared to longer track sessions, can still manifest as a reduction in braking effectiveness due to heat build-up. Choosing pads with an appropriate heat range for your specific application is crucial. For autocross, pads that offer good initial bite and consistent performance without excessive heat generation are generally preferred. Understanding the friction coefficient of different compounds can help you select pads that match your car's tyre grip and your driving style.
Maintenance for your braking system is paramount. Regularly inspecting your brake pads for wear, checking brake fluid levels and condition, and ensuring your rotors are in good shape will prevent unexpected issues and maintain optimal performance. For autocross, where braking is frequent and often abrupt, keeping your braking system in top condition is essential for both safety and competitive results.
Frequently Asked Questions (FAQ)
Q1: Do I need high-performance brake pads for autocross?
While not strictly mandatory, high-performance pads can offer improved initial bite, better heat management, and more consistent pedal feel, which can be advantageous when paired with sticky autocross tyres.
Q2: What is brake fade in autocross?
Brake fade occurs when brake pads overheat, reducing their friction coefficient and thus their stopping power. While less common in short autocross runs, it can happen during intense sessions or with aggressive driving.
Q3: How do I bed-in new brake pads?
The bedding process typically involves a series of moderate-to-hard stops from increasing speeds, followed by a cooldown period. Always follow the specific instructions provided by the brake pad manufacturer.
Q4: Will better brake pads make me faster in autocross?
While brake pads can improve your confidence and consistency, the biggest gains in speed usually come from driver skill and tyre performance. However, well-matched brake pads can help you utilise the available grip more effectively.
Q5: What are the signs of worn brake pads?
Common signs include a squealing or grinding noise when braking, a longer stopping distance, and a spongy or low brake pedal. Regular visual inspection is recommended.
If you want to read more articles similar to Autocross Braking: Pads, Fade, and Performance, you can visit the Brakes category.