Ten myths about Nascar and the brakes they use. Not as far behind Formula 1 as you might think

6/5/2019

The NASCAR Cup Series is the arena par excellence for spectacular entertainment: the format of the championship, the minimum differences between the teams' budgets and the similar performance of the 3 engines used work together to level the playing field, resulting in extremely close and unpredictable races

The Grand Prix may not be much of a spectacle on the track, but it is full of cutting-edge technology, with new technical solutions on its single-seaters almost every year. While Formula 1 is unquestionably world king of motorsports classes, its very nature makes for a lack of balance, with only three teams scoring one or more wins since 2015.

The Nascar Cup Series, on the other hand, is all about spectacle, as shown by the fact that 12 different drivers won at least one race in 2018. The format of the championship, the minimal differences in budget between teams and the similar performance of the three engines used in the class contribute to creating a level playing field, producing races with minuscule leads and where the end result is unsure right up to the checkered flag.

Many believe, however, that the Nascar Cup Series only achieves this balance by restricting technological evolution and using outdated technical solutions to maintain the status quo. In reality, the imposing weight of the cars in this class (3,393 lbs including driver and fuel) drives teams to search constantly for new technological solutions.

What is most surprising for anyone who does not follow the Nascar Cup Series is the amount of attention dedicated to the brake systems, in terms of engineering and how they are used during the race. So we have picked 10 myths about the brakes in the Nascar Cup Series, and debunked each one with real facts.

1) Formula 1 cars use their brakes more than Nascar Cup Series cars. FALSE

In Formula 1, the brakes are used for between 13 and 27 per cent of the total lap time. The lowest percentages are at Monza and Spa-Francorchamps, where the brakes are applied for 10.5 and 13 seconds respectively. At Spielberg, the brakes are used for a total of 9.8 seconds per lap, but as it is a quicker circuit, this equates to 15 per cent.

In the Nascar Cup Series, the differences between different tracks are much more pronounced. On the big oval circuits like Talladega and Daytona, the drivers do not use the brakes at all, except when slowing down to come into the pits or in the event of a crash. On shorter ovals, such as Martinsville, the drivers use the brakes for approximately 7 seconds for each of the two turns. Considering a lap time for this circuit of around 20 seconds, this means that the brakes are in use 70 per cent of the time.

2) Brakes don't play a decisive role because all Nascar races are on oval circuits. FALSE

As from 2018, the season includes three races on road circuits, with the cars of the Nascar Cup Series racing at Sonoma Raceway (a 2 mi circuit with 10 turns), at Watkins Glen (3.4 mi, 11 turns) and at the Charlotte Motor Speedway (2.3 mi, 17 turns). In September 2018, the Charlotte Motor Speedway became the first road circuit to be used in the playoffs, proving the growing importance of these tracks in the championship.

The brakes are used extensively on these circuits, with the cars slowing before almost all the turns. On average, the brakes are used for a total of around 20-30 seconds per lap, equating to 30 per cent of the duration of the race. To avoid overheating, at Watkins Glen the cars use Brembo discs with 0.87 inch-wide ventilation channels.

3) Nascar brake discs are outdated because they're not made from carbon. FALSE

One of the key differences between Formula 1 discs and Nascar Cup Series brake discs is the material they are made from. Carbon is banned in the US series, so the cars use cast-iron discs. Some may say this is a sign of technological backwardness, but they ignore just how much constant research and experiments Brembo conducts on the many variables and characteristics of cast-iron discs. This starts with disc ventilation, which involves designing ventilation channels that cool the discs during races. The computer-modeled, static and dynamic tests conducted by Brembo to determine the dimensions, shape, number and curvature of these channels are no less sophisticated than the ones done for the holes in carbon discs.

The mounting systems connecting the brake rotor to the hat are also optimized to prevent warping and fracturing caused by overheating. Brembo dedicates just as much attention to research and experimentation into the design of the surface treatments for the cast iron discs of the Nascar Cup Series and the application methods used. One should also not underestimate the importance of the chemical composition of the cast iron itself, which is the result of continuous experimentation. And precisely because cast iron is the subject of all of this research, the benefits can be extended to the discs used on the most widely sold American road cars.

4) As in F1, the braking systems are the same for all the tracks. FALSE

Unlike Formula 1, where each team uses the same model of brake caliper for the whole season (allowing, of course, for technological evolution during the season itself), in the Nascar Cup Series, the three different types of oval course call for three different types of brake caliper, due to differences in how the brakes are used. On Super Speedways (ovals of 2.5 mi inches and more in length), the brakes are never used except to enter the pit lane or when a yellow flag is shown. On Intermediate tracks (1-2.5 mi tracks) the brakes are used very sparingly, whereas on Short Tracks the braking system is used throughout the entire turn.

As a result, on Super Speedways the calipers are smaller, on Short Tracks they are bigger and on Intermediate tracks they are somewhere in between. Moreover, while in Formula 1 the size of the discs used is the same throughout the year and only the configuration of the ventilation holes changes (with a choice of medium cooling, high cooling and very high cooling configurations with 800, 1,250 and 1,480 holes respectively), in Nascar, the diameter and thickness of the front discs change depending on the type of circuit.

5) Deceleration has increased less than in Formula 1. FALSE

Over a decade, maximum deceleration in Formula 1 has increased by approximately 10-14 per cent. This is demonstrated at the first turn in the Italian GP at Monza, known as the Chicane of the Straight, or Variante del Rettifilo, at the beginning of which the deceleration sustained by drivers has gone from 5 g in 2009 to 6.7 g in 2018.

The braking systems in Nascar Cup Series cars have also improved significantly over the past decade, benefiting from Brembo know-how acquired over 40 years of racing. Despite having only four pistons, today's calipers deliver exactly the same braking power as the six-piston calipers of the previous decade. Improvements in discs and pads, on the other hand, have brought an average increase of around 20 per cent in deceleration.

6) The braking systems are identical for all drivers. FALSE

In Formula 1, each team works in conjunction with Brembo's engineers to define the ideal balance between the weight and stiffness of the brake calipers in accordance with the specific needs of the car. Some teams prefer lightness over stiffness, while others opt for more conservative solutions which are stiffer but, as a result, heavier. This delicate balance means that Brembo has to develop a completely bespoke braking system for each team.

Many are not aware of that fact that each Nascar Cup Series team also asks Brembo to develop pretty inspired personalized solutions for their braking systems. And as the drivers in a single team can have very different braking styles (some adopt an open-wheel racer approach, with a very intense initial braking force which then gradually tapers off, while others prefer the opposite), two teammates might use different friction materials.

In this case, the custom solutions developed by Brembo concern the friction materials used and the ventilation system, diameter and thickness of the discs rather than the calipers, depending on the aerodynamic requisites of the individual cars. To meet this need, Brembo develops custom solutions for the disc ventilation channels.

7) In the Nascar Cup Series, the brakes are only used to slow down. FALSE

Right from his debut in Formula 1, Michael Schumacher astonished everyone with his ability to brake and accelerate at the same time, using both feet simultaneously: with his right foot on the throttle and the left on the brake. This let him enter turns at higher speeds than his competitors, earning precious hundredths of a second at each curve on the track.

On the big oval circuits of the Nascar Cup Series such as Indianapolis, Daytona and Talladega, when drivers are bumper to tail with the car in front, to avoid a collision, they touch the brakes gently without lifting off the accelerator. This lets them keep the engine at full throttle and not lose precious power. On small ovals, on the other hand, as well as for slowing, the brakes are also used to help the car turn more effectively.

8) The calipers used in Nascar Cup Series only reach low temperatures. FALSE

In Formula 1, on circuits with many braking points in rapid succession, such as the Monaco and Hungarian GPs, the aluminum-lithium calipers can reach temperatures up to 392°F. On other tracks, the calipers reach peak temperatures of 302-320°F. This heat is dissipated instantaneously, however, as very high temperatures can cause the alloy to lose stiffness.

In the Nascar Cup Series, on the other hand, the caliper temperatures can reach temperatures of up to 440°F. The pads and discs get even hotter, reaching temperatures of 1600 and 1800°F respectively. This is made possible by Brembo HTC 64T brake fluid, which has a higher boiling point (635°F) than any rival product.

9) Nascar calipers are much heavier than their F1 and GT counterparts. FALSE

You'd expect the brakes needed to stop cars weighing over a ton and a half to be huge. And yet the six-piston Brembo monobloc front calipers for Short Tracks weigh just 6.2 lbs and the four-piston front calipers for Super Speedways weigh no more than 5.07 lbs. The rear calipers are even lighter: weighing in at 4.4 lbs for Short Track versions and 3.3 lbs for Speedways, for which teams can even choose a Light variant tipping the scales at just 2.64 lbs.

These latter values are comparable to those for the front calipers in Formula 1 and Formula E.

10) The brakes in the Nascar Cup Series do not wear much over a race. FALSE

During a Formula 1 Grand Prix, carbon pads and discs wear by less than 0.04 inches. On the prototype cars racing in the 24 Hours of Le Mans, which also use carbon friction material, each disc and pad loses 0.12-0.16 and 0.31-0.39 inches respectively over the 24 hours of the race.

However, these values are nothing in comparison to the average 0.35 inches of pad wear seen at Martinsville, and the 0.43 inch wear at Watkins Glen. These two values offer even further proof of the far from minor role played by brakes in the Nascar Cup Series.