NASCAR to implement new rules for less downforce

UPDATE Tuesday's NASCAR technical bulletin, which contained a laundry list of rule changes in eight areas, was significant enough that crew chiefs immediately began booking wind tunnel time. Of greatest interest was the shortening of the side skirts on the Cup cars, designed to create greater ground clearance. NASCAR also has mandated use of superspeedway-sized stationary air deflectors (commonly known as "shark fins") on all tracks of two miles or more.

According to Robin Pemberton, NASCAR's vice president of competition, the rule changes were inspired by work on the 2013 car, with an eye toward raising the speeds at which a car will lift off and become airborne.

One byproduct of the shortening of the side skirts will be a loss of downforce and a possible decrease in the stability of the cars in traffic. Just how much downforce the Cup cars will lose is an open question, and there's no firm consensus among crew chiefs as to what the number will be, even though several teams already have tested the changes in wind tunnels and during a Goodyear tire test at New Hampshire earlier this week.

There's also a consensus that the changes to the side skirts will force changes to the suspensions of the cars — particularly to the rear suspensions — as crew chiefs try to recreate the "seal" (or close proximity) between the side skirts and the pavement as a method to recover downforce. NASCAR Wire Service

05/12/12 Trying to reduce downforce and the chance of cars becoming airborne, NASCAR will implement a pair of rules changes for Sprint Cup teams that may also produce more passing. One change will go into effect starting next week at Charlotte Motor Speedway. The side skirts-the body of the car between the wheels-will be higher above the ground, meaning more air will run underneath the car.

Currently, the skirts must be 3 to 4.5 inches off the ground on both sides of the car. Starting next week, they must be 4 to 4.5 inches off the ground on the right side and 4.5 to 5 inches on the left side. Teams tested with the shorter side skirts during recent Goodyear tire tests.

For tracks 2 miles or larger, NASCAR will use its longer "shark fin"-a panel that runs alongside the rear window and decklid of the car-that has been used at Daytona and Talladega to keep cars from getting airborne. On the short tracks, it will remain a minimum 17 inches long while they must reach all the way from the top of the car to the spoiler on tracks 2 miles or longer. This also will decrease the potential of car liftoff, which could have been an issue at some of the most recently repaved tracks-the 2.5-mile track at Pocono and 2-mile track at Michigan. Sporting News