What Does A Wedge Adjustment Do And Why Aren’t Tires As Important At Daytona? NASCAR PHYSICS

Daytona International Speedway is perhaps the track most synonymous with NASCAR racing. Home to the iconic Daytona 500, NASCAR has been racing on the high banks of Daytona since 1959. The speedway was originally conceived of by NASCAR founder Bill France Sr. in 1953 as a way to promote his fledgling racing series which was currently racing on the sands of Daytona Beach. France Sr. wanted to build the biggest, highest bank speedway for two purposes. He wants to see ridiculous top speeds, and he wanted fans to be able to see the cars from far away as they traversed the banked corners.

The Daytona Beach road course was engineered by Charles Moneypenny and France Sr. enlisted his help again to build the permanent superspeedway. Moneypenny eventually patented a new method of paving which involved anchoring the paving equipment to a bulldozer situated at the top of the banking to prevent the paver from sliding down the incline or tipping over. This method was also utilized when paving Talladega Superspeedway and Michigan International Speedway. To build the banked corners, over one million yards of soil had to be excavated from the infield and compacted to form the corners. The pit left behind, now known as Lake Lloyd, was filled with water, stocked with fish, and used to host power boat racing.

With one year left to go in construction, Bill France Sr. was beginning to run out of capital. He approached the Coca-Cola company about sponsoring the project and was turned down. He then approached their competitor Pepsi Co who agreed to help finance the completion of the project. From 1959 until France Sr’s death in 1992, no Coca Cola products were allowed to be sold at the speedway.

The 1959 Daytona 500 was run in front of a crowd of 42,000 spectators and concluded with a photo finish that took three days to adjudicate due to photo development time constraints and the lack of electronic scoring. Two months later the speedway hosted a 100-mile Champ Car race which concluded with an average speed of 170.26 mph making it the fastest motor race in history at the time.

Through the years, Daytona has been home to some of the sports most iconic moments of both triumph and tragedy, but never more so than during the 2001 season. After the death of Dale Earnhardt Sr on the final lap of the Daytona 500 in February, NASCAR returned for the first time that July to run the Pepsi 400. The race featured an electrifying finish that saw his son Dale Earnhardt Jr take the win in a powerful moment of healing for the sport as a whole.

(Watch the video above at about 21 minutes to see this happen).

For more information on how drafting works out, and driving techniques at a superspeedway, check out my piece on Talladega Superspeedway.

It’s All About Gas, Gas, Gas

So, what does it take to find victory lane in Daytona? Fuel is the name of the game here. Handling is a minimal issue, especially at the summer race which takes place during cooler evening conditions for both the Cup and Xfinity Series. As such, there isn’t any advantage in terms of lap time when a team puts on fresh tires. The only advantage is that fresher tires will provide slightly more grip when a driver has to make abrupt lane changes in the draft. Because fuel is more important than tires, the whole race becomes a game of taking as little fuel as possible at each pit stop.

The stage breaks provide a window for predetermined pit stops, but cautions during the stages give teams an option to get off sequence with the rest of the field. If the caution comes out towards the end of a stage, a team can opt to pit then and stay out when the rest of the field pits at the stage break. This will obviously cycle them to the front of the pack for the next stage but with the caveat that they will need more fuel on the following pit stop. The whole race is about managing your fuel windows to be able to take the least amount of fuel at the final pit stop to set you up for a dash to the finish.

Superspeedway racing in 2024 has evolved to be almost like a road course race where a team’s strategy is worked out backward from the beginning of the final fuel window. The strategy aspect of superspeedway races is much more important in Daytona than it is at Talladega. Despite being similar in layout, Daytona is eight feet narrower than Talladega. This makes it more difficult to form a third line or make any sort of progress through the pack. Comparatively, Daytona requires a much more calculated approach than Talladega. As such, the races have begun to develop a familiar cadence. If we plot out the average occurrence of natural cautions over the course of a race for the last three summer Daytona races a trend begins to emerge.

The first stage usually has some frantic action for the first roughly ten laps as drivers settle in and feel out their cars. Drivers quickly settle into formation and typically tend to log some laps until the end of the first stage approaches. Somewhere around five to go, drivers outside of the top ten will start trying to make their way forward to capture some stage points and this is right about when we have the first caution flag of the race.

The second stage tends to have less riding than the first because the stage break caution eats up some of the opening laps. The same pattern tends to exist, however. Restart, franticly try to get as many spots as possible on the opening laps. Save fuel and ride for a minute. Race your ass off for some stage points.

You can see from the chart above that the final stage is where things start to get wild. Once the final pit stops have been made it’s every driver for themselves, strategy be damned, which is why we see the increase in cautions. As the finish approaches, blocks will get more aggressive, moves will be made more decisively, and eventually someone will get turned sideways in front of the pack. Statistically, the most dangerous place to be is between sixth and twentieth. A bad block towards the front usually causes an accordion-like stack up and some pour soul in the back half of the top ten gets the worst end of it.

How Do You Actually Save Fuel?

Speaking of fuel savings, how does a driver manage to do that? In the Cup Series, with their modern, fuel-injected engines it’s a bit simpler. Through SMT data the teams can see exactly how much throttle the driver is using in real-time and this can tell them whether they are saving too little, too much, or just right. For the Xfinity Series teams, things are a bit trickier. Because the Xfinity cars are still carbureted, the SMT data doesn’t have an “actual” throttle position available. The assumed throttle position is interpolated based on accelerometer data which is questionable at best but borderline useless for fuel savings.

At a standard race track, teams can use a lap time delta to determine roughly how much fuel has been saved. For drafting tracks, that’s basically useless. Teams must tell the drivers how much to save and rely on their experience to get them there, but it’s still not quite that simple. If a driver is rolling in and out of the throttle to maintain their gap in line with the car in front of them, they are wasting a tremendous amount of fuel. This is because on initial throttle input the carburetor kind of surges the motor with fuel and not all of it can be burnt. The best way to save fuel in one of these carbureted cars is to pick a constant throttle position, maybe somewhere around 60% throttle, and use the brakes to maintain gaps to the car in front of them rather than lifting out of and reapplying the throttle. A driver may tell their team that they’ve done a great job saving and haven’t gone wide open the whole run but if they’re constantly in and out of the throttle their fuel mileage will be significantly worse than what the team may have calculated.

There are a number of other things that make the Xfinity series race kind of “funky” at superspeedways. First, we must clarify something that can be kind of confusing. During the last two races at Indianapolis Motor Speedway and Michigan International Speedway, the series used a semi-super-speedway package. What I mean by this is that while the cars had the reduced horsepower superspeedway engine, the body and suspension rules were the same as any other oval. At Daytona International Speedway and Talladega Superspeedway we use the “full” superspeedway package which combines the reduced horsepower with a different body style and different rear suspension rules.

With the full superspeedway package, NASCAR supplies the rear springs and shocks to Xfinity series teams upon arrival at the track and strictly controls their installation angles into the car. The purpose of this is to increase rear ride heights, which puts more air onto the spoiler thus increasing drag and decreasing speed. Teams have a lot of theories about how to make these springs act as softly as possible, but I like my job so I’m not going to put the specifics onto the internet, sorry, lol. For more information on the specifics of these components, you can check out my piece about Talladega Superspeedway.

Giving The Car A Wedge-ie

So, how does this rule package affect the strategy and why does it make the race so weird? When watching a race, you may have seen a crew member put a wrench into the rear window, or heard radio communication about “rounds” of wedge and wondered what exactly was going on. Below, you can see a generic Xfinity rear suspension as described by the NASCAR rule book.

The bottom of each rear spring (I-9) sits upon the trailing arm (also known as a truck arm), the left side trailing arm is tagged #2. The top of the spring sits against an upper spring perch (I-10) whose height can be adjusted up and down by a jack screw (I-8). The jack screw is threaded through the rear clip and has a mandated thread pitch of 12 threads per inch. The unlabeled top piece of the jack screw is the rear window extension where a crew member can insert a wrench during a pit stop and turn the jack screw.

The bottom of the spring sits on the trailing arm, which is connected to the tire and therefore the ground so you can consider its height fixed. As the jack screw is turned up or down it either loads or unloads the spring and adjusts the height of the car accordingly. A thread pitch of 12tpi means that the spring pre-load is adjusted 0.083” (0.21cm) per round. The Xfinity superspeedway rear springs have a rate of 450lb/in (80.3kg/cm) so one round of the jack screw changes the spring’s preload by 37.4lbs (16.9kg).

During pre-race inspection at a superspeedway, the rear spoiler height must be between 44.06” and 44.31” (111.91cm and 112.55cm). After a car has passed height checks, the rear jack screws are sealed by a NASCAR official. The jack screws will remain sealed during qualifying, and an official will remove the seal on the grid as drivers are getting buckled into the car. For qualifying purposes, teams will try to set their car as close to the minimum rear-ride heights as possible.

The post-race inspection window is opened up by 0.5” on both sides meaning that the spoiler must be between 43.56” and 44.81”. Teams will calculate how many “rounds” they can remove from the rear suspension to get their car from pre-race heights to just slightly above post-race minimum. In the event of an early caution, you will often see multiple cars come down pit road, even as early as lap two or three. To the uneducated observer this would seem crazy, but what these teams are doing is pitting to lower the rear suspension and get their car into “race” trim as early as possible. Even if the team gives up their track position by pitting on the first possible caution, they will have a significant speed advantage over cars that have not yet pitted for their adjustments and will ideally be able to recover quickly.

Gimme A Brake

Another side effect of this NASCAR-mandated rear spring and dampers combination comes into play during pit stops. Teams are allowed to run their own front dampers, and they will typically run what are called “tie down” dampers. This style of damper has minimal compression and massive rebound resistance. Basically, once the front suspension travels down, the dampers will prevent it from coming back up to help seal off the splitter to the racetrack. NASCAR’s specified rear dampers do the opposite as they want the back of the car to travel backward, aided by the rear suspension, with the nose held down more than usual by the front dampers. This often causes the front splitter to make contact with the racing surface. If the splitter is on the ground, then it is taking some of the load off of the front tires, which make them more susceptible to locking under braking. If you’re listening into a team’s radio scanner, you will likely hear a driver be reminded to adjust their brakes prior to a pit stop. What they’re doing is moving some of the brake bias towards the rear of the car to avoid front lockup. Without adjusting the brakes, it would be very easy for a driver to slide through their pit stall, or to be speeding on entry to the pit lane during a green flag stop.

While green flag pit stops are less common in the Xfinity series, both Xfinity and Cup drivers will face challenges in getting onto pit road. The Cup series drivers don’t have to worry about their splitter bottoming out, but drivers in both series must be very careful with their braking on pit lane entry. Teams utilize the smallest brake package of the year at superspeedways. Smaller rotors reduce rotational inertia while smaller pads and calipers reduce drag in the system and improve rolling resistance.

Because drivers don’t need to use the brakes in order to get around the racetrack, there is very little heat in the braking system during green flag conditions. This means that when entering pit road under green flag conditions, the brakes will be heated tremendously from their baseline state. Drivers must be careful to get some amount of heat into their brakes in the laps prior to their planned pit stop. They can do this by lightly dragging the brake pedal while holding the throttle wide open. If the brakes aren’t preheated for pit lane entry, they will actually gain stopping power under braking as the temperature increases. Even if the driver keeps their pedal pressure constant, the braking force will increase and can cause a tire to lock up.

When coming to pit road at a superspeedway you will normally hear a team remind their driver not to slide their tires. Even a slight lockup can completely derail a team’s strategy by forcing them to change tires. Most of the time, a late pit stop will be planned for fuel only. Even if the refueling time is slightly greater than the time it would take to exchange tires, you will often see teams forego fresh tires and stick with fuel only. As I mentioned early, fresh tires are only a slight benefit, but the added risk to a pit stop is significant. Imagine for example a team only needs six seconds of fuel on a pit stop. This would easily be enough time to change right-side tires, but most of the time teams will consider that not to be worth the risk. A slow tire exchange that adds time to the pit stop will completely undermine all of the fuel savings that the driver had done that run. Even worse, a loose wheel would certainly take them out of contention as coming back down pit road alone will take their driver out of the draft.

It takes the whole package, a perfect strategy, and a little bit of luck to find victory lane down here in Daytona. Tune in this weekend to see which teams can get it right.