Superspeedways get restrictor plate changes

Power-reducing carburettor restrictor plates are mandatory at the 2.5-mile Daytona and 2.66-mile Talladega superspeedways in order to keep lap speeds below the 200mph mark, but are unpopular with the drivers. With the whole of a lap run on full throttle, overtaking is difficult and the field tends to stay bunched together in multi-car packs - leading to several major crashes in recent seasons.

But following a series of drafting tests at Daytona in August involving several leading drivers, NASCAR will reduce speeds by increasing aerodynamic drag, but giving some power back. The new rules will be in place for Talladega's Winston 500 on October 15.

Drag will be increased by raising rear spoiler angle from 45 degrees to between 70 and 71 degrees, adding a one-inch 'Gurney tab' to the rear spoiler, and fitting a 40-inch wide air deflector to the roof of each car. Front air dam height will also be increased by 0.5 inches, while Pontiac and Ford will have their rear spoiler width increased from 57 to 59 inches. Chevrolet's spoiler width will stay unchanged.

Restrictor plates will be increased from 7/8 inches to one inch, allowing more air into the carburettor and increasing power by approximately 75bhp. Current restrictor plate engines deliver around 450bhp, compared to 750bhp for a non-restricted engine.

NASCAR believes that as well as keeping speeds below the 200mph mark, the new rules will force drivers to come off the throttle more into corners and also make overtaking easier by reducing the reliance on multi-car drafts to pass other cars. With drivers theoretically more able to carry out single-car passing manouevres, the changes should also break up the multi-car packs.