In motorsports, a pit stop is where a racing vehicle stops in the pits during a race for refuelling, new tires, repairs, mechanical adjustments, a driver change, or any combination of the above. Not all are allowed in all formulae.
The pits usually comprise a pit lane which runs parallel to the start/finish straight and is connected at each end to the main track, and a row of garages (usually one per team) outside which the work is done. Pit stop work is carried out by anywhere from five to twenty mechanics (also called a pit crew), depending on the series regulations, while the driver waits in the vehicle (except where a driver change is involved). In American racing series, a pit lane consists of a number of pit stalls and a concrete pit wall which separates the pit lane from the infield, with the garages on a separate road in the infield; European racing series typically have the individual garage stalls open directly onto the pit lane through the team's assigned pit stall. In American English, it is common to drop the definite article and just refer to "pit lane", whereas in British English one would always refer to "the pit lane".
By making pit stops cars can carry less fuel, and therefore be lighter and faster, and use softer tires that wear faster but provide more grip. Teams usually plan for each of their cars to pit following a planned schedule, the number of stops determined by the fuel capacity of the car, tire lifespan, and tradeoff of time lost in the pits versus how much time may be gained on the race track through the benefits of pit stops. Choosing the optimum pit strategy of how many stops to make and when to make them is crucial in having a successful race. It is also important for teams to take competitors' strategies into account when planning pit stops, to avoid being "held up" behind other cars. An unscheduled or extended stop, such as for a repair, can be very costly for a driver's chance of success, because while the car is stopped for service, cars remaining on the track can rapidly gain distance on the stopped car.
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In any racing series that permits scheduled pit stops, pit strategy becomes one of the most important features of the race; this is because a race car traveling at 100 miles per hour (160 kilometers per hour) will travel approximately 150 feet (45 meters) per second. During a ten-second pit stop, a car's competitors will gain approximately one-quarter mile (one-half kilometer) over the stopped car.
However, the car that made the additional pit stop will run faster on the race track than cars that did not make the stop, both because it can carry a smaller amount (and thus lower weight) of fuel, and will also have less wear on its tires, providing more traction and allowing higher speeds in the corners. In racing series where teams have their choice of different compound tires, the lower tire wear may be enough to allow the team to choose to use a tire with a softer rubber compound that provides increased grip at the expense of faster wear; going longer between stops may even cause enough wear on the softer tire to cause the tires to fail.
Because of this, race teams plan a pit strategy prior to the start of every race. This is a schedule for each car's planned pit stops during the race, and takes into account factors such as rate of fuel consumption, weight of fuel, cornering speed with each available tire compound, rate of tire wear, the effect of tire wear on cornering speed, the length of pit road and the track's pit road speed limit, and even expected changes in weather and lighting conditions. The pit strategy does not just include a schedule of when pit stops will happen; it also includes what service and adjustments are scheduled for each pit stop, particularly in endurance racing, where scheduled changes of wear-limited parts such as brake pads may be planned for specific points during the race. The pit strategy is calculated carefully so that the amount of time to be "given away" to other competitors in pit stops is balanced out by the time gained while on the track, resulting, theoretically, in the shortest possible time to cover the scheduled distance.
However, a team's pit strategy is not a fixed, immutable thing; it is subject to change during the race to take into account the unpredictable events that happen in every race. In road racing, for example, if the weather changes from dry to rain, teams will be forced to recalculate their pit strategy based on the unscheduled stop to change from dry-weather "slick" tires to treaded wet-weather tires. Full-course caution periods often see mass pit stops by many teams, hoping to take advantage of the slowed pace to reduce the ground lost to other teams while making pit stops; this forces teams that do so to immediately recalculate their pit strategy to optimize it for the remaining race distance after the stop.
Even when a team chooses not to take advantage of the opportunity to stop during a full-course caution, it can still result in significant changes to pit strategy; under caution, the cars run at a reduced speed that results in greatly reduced tire wear and fuel burn for a distance traveled. Depending on the circumstances, this may be enough for a team to gain more by choosing not to pit, hoping that the reduced fuel burn and tire wear will allow them to make one pit stop fewer than the other teams, allowing them to gain distance and time on their opponents. At tracks noted for frequent full-course cautions, teams may even plan their entire race strategy around this, using a suspension and aerodynamic setup suited to short sprints instead of extended runs to gain positions in the short bursts of green-flag racing, and planning their pit strategy on the assumption that cautions will extend their fuel mileage and tire wear enough to make fewer stops than would otherwise be needed to complete the race distance.
During a scheduled pit stop, the team's pit crew services the car as swiftly as possible, completing a number of different services. The most visible services performed are refueling the car and changing tires.
Other services performed in routine pit stops include removing debris from radiator air intakes; cleaning the windshield; and making adjustments to tire pressure, suspension settings, and aerodynamic devices to optimize the car's performance for the current conditions. In endurance racing, scheduled driver changes and brake pad replacements are also considered "routine" service when done as part of a scheduled pit stop.
An unscheduled pit stop may see other service performed; because unscheduled stops are usually due to damage or mechanical problems, they frequently see emergency repairs performed on the car. These tend to have extremely long duration, due to the need to diagnose the car's problems prior to the time-consuming repairs.
In Formula One, mid race refueling is currently not permitted by the regulations, and cars make pit stops with the primary purpose of changing tyres. Teams sometimes also make adjustments to the front and rear wings and perform minor repairs, most commonly replacing the nose and front wing assembly. Pit strategies generally call for between one and three scheduled stops, depending on the circuit. The driving between pit stops are commonly known as 'stints'.
When the car is approximately one lap away from making its stop, the team's pit crew will set up fresh tires and all needed pit equipment. Because of the overhead pneumatic rig, the team may have all pit mechanics in position prior to the car's arrival, with the exception of the rear jack man.
Interestingly, unlike almost all other forms of racing that feature routine pit stops, Formula One rules limit teams to a single pit crew for the mandatory two cars entered. Therefore, teams must stagger their pit schedules so that only one of their two cars is in the pits at any given time. Most other racing series that feature routine pit stops permit each car its own pit stall and crew.
Refueling was permitted from the 1994 season until the end of the 2009 season. During this period, a pit stop involved about twenty mechanics, with the aim of completing the stop as quickly as possible. Stops generally lasted for six to twelve seconds depending on how much fuel is put into the car. However, if there is a problem, such as a fuel pump failing or the engine stalling, or repairs having to be made, it can take much longer. Cars were fueled at a rate of more than 12 liters per second. This is accomplished by a fairly complex closed system that pumps air out of the car's fuel tank as the fuel is being pumped in.
As refueling is a potentially hazardous situation, the mechanics wore fire-resistant multi-layer suits & flame-resistant gloves, long underwear, balaclava, socks and shoes, which have to meet the guidelines set by FIA Standard 8856-2000.[1]
Crew chiefs lead the pit crew during pit stops in addition to coaching the driver during the race. Pit crew members were once the mechanics on the racecar, but most teams feature individuals dedicated to pit stops only, and often former collegiate or professional athletes are used for pit stops. Former NFL player Tim Goad is regarded as the first former professional athlete involved in a pit crew, as a jackman. Nonetheless, pit crew members work with the team in fabricating or designing the race cars during the week while training for their "pit job" on the weekends.
Teams will be penalized if the car is serviced outside of the designated pit stall, if the car drives over an air hose, or if any of the old tires are not on the pit wall side (usually left) of the vehicle's centerline before the car leaves. If a car stalls, the pit crew may provide a push start, but the car cannot be pushed beyond three pit stalls ahead of its own, or beyond the paddle man at the end of pit road. A pit stop for four tires and fuel can last 12–16 seconds, and a stop for two tires and fuel may take 5–7 seconds. These times depend upon any suspension adjustments performed and the quality of the crew.
NASCAR Sprint Cup Series team pit strategies vary widely, depending on the track. Fuel is generally a more limiting factor than tire wear, and the phrase "fuel window" or "pit window" is used to indicate the maximum number of laps possible with a full load of fuel, assuming continuous green flag conditions and a small reserve. The window is used to calculate (or recalculate after a stop) the minimum number of pit stops required to complete the race. The road courses on the schedule may see as few as two scheduled stops; oval race tracks generally see between four and six scheduled stops. Races at short tracks such as Bristol Motor Speedway and Martinsville Speedway are short enough to be completed with only two scheduled stops for fuel, but teams plan on more stops due to rapid tire wear and significant loss of cornering speed on worn tires.
In the IndyCar Series, a pit stop is a more complex operation than in NASCAR, but far less so than in Formula One. Rules permit six mechanics over the pit wall during a stop. The pit rules and procedures have origins in USAC National Championship racing.
During a routine pit stop in either series, the tires are laid out and three of the four tire changers are pre-positioned before the car enters its pit stall; the fourth tire changer, whose responsibility is the rear tire on the far side of pit road from the pit wall, doesn't take his position until after the car arrives, due to a rule against having the car run over the feed hose for the impact wrench used to change the tires.
After the car arrives, the first step, taken while the fourth tire changer takes his position, is for a mechanic to insert the "vent hose" into its socket on the engine cowling. This hose vents the air out of the fuel tank, captures any overflow fuel, and also activates the car's built-in pneumatic jacks. After the vent hose is in place, another mechanic attaches the refueling hose to its socket, allowing the ethanol fuel to flow into the fuel tank. Simultaneously, the four tire changers remove the tires and install the new ones. After the tire changes are complete, the front tire changers may use manual adjusters to adjust the angle of the car's front wing.
After the tire changes are complete, the vent hose is removed, allowing the car to return to its wheels. However, the driver usually must wait until the fueling is finished and the fuel hose is removed from the car. The right front tire changer (who is usually also the crew chief) signals the driver when the stop is complete. Before the car departs its pit stall, a crew member must use a squirt of water to wash any excess fuel from the fuel hose and vent hose sockets; this is usually done with a pressurized hose by a crew member behind the pit wall.
Under normal conditions, a routine stop for an IndyCar team lasts between ten and fourteen seconds. IndyCar teams are permitted to set their own pit strategies.
In the various forms of sports car endurance racing, pit stops are a more leisurely affair, but no less important than in other forms of racing. While stops take longer, much more routine maintenance is scheduled during such pit stops, needed to keep the car running for as long as twenty-four hours; this includes major aerodynamic changes to deal with the changing temperature in such a long race, and replacement of certain wear-limited parts, such as brake pads. Due to the fact that the race is scheduled to last a certain length of time rather than a specific distance, pit strategies are generally not designed to be synchronized with the race distance, but rather to happen on a schedule based on the car's requirements for routine service.
Under the rules of the Automobile Club de l'Ouest (ACO) {used by the American Le Mans Series and Le Mans Series} only five mechanics are permitted to work on the car. One man is permitted to fuel the car; all fueling must be completed before any other service occurs. The other four mechanics on pit lane at any given time are typically two tire changers and two tire carriers, each of whom handles his task on only one side of the car. Automatic pneumatic jacks are used, integrated into the car itself.
The Grand American Road Racing Association allows only four mechanics to service a car during a pit stop. One crew member will refuel the car while the other three are responsible for changing tires and operating the pneumatic jacks. A fifth crewmember must serve as the teams designated firefighter and must stand ready in the pit stall with a fire extinguisher while the car is being refueled. A sixth crewmember may assist in a driver change. Neither the firefighter or driver's assistant may perform any additional service to the car itself.[2] Unlike the ACO, Grand-Am does not force crews to wait for fueling to complete before changing tires.
In endurance racing, driver changes are mandatory; the shortest endurance races are scheduled for four hours, one hour longer than the longest nonstop time permitted behind the wheel. During a pit stop with a driver change, the new driver and a driver change assistant are permitted into the pit lane. The assistant, who may not do any mechanical work on the car, is tasked with helping the current driver out of the car, removing or swapping driver seat inserts, helping the new driver into the car, and helping the new driver tightly fasten his safety harness and connect his various helmet connections to the car's systems, including the two-way team radio and the drink bottle used to stave off dehydration.
A routine pit stop with no scheduled maintenance and no driver change generally lasts from thirty to forty seconds. With a driver change included, that time increases by about ten seconds. Should there be significant scheduled maintenance, such as changing brake pads, the stop can easily last well more than a minute.
Unlike most other forms of racing, the rules of endurance racing require that the car's engine be shut off during the stop. Another difference from most forms of racing is found in the practice of "double-stinting" or even "triple-stinting" tires; tires hard enough to withstand the rigors of racing in the heat of the daytime may be so hard that they do not wear significantly during the nighttime hours. In a race where this is an issue, significant time can be gained by choosing to leave worn tires on the car during the first stop after they were put on the car; if the temperature drops low enough, teams may even be able to go two pit stops without changing tires.