NASCAR took action Friday after high speeds at Talladega Superspeedway prompted concerns from drivers and teams.
The sanctioning body mandated the addition of a 1-inch wicker to the rear spoiler in a bid to reduce speeds after 21 cars averaged 200 mph or more in the first Monster Energy NASCAR Cup practice session of the weekend.
Closing speeds were even higher — according to Autosport.com, several teams reported speeds of more than 208 mph in those situations.
"The closing rate, based on my memory, is the highest it's ever experienced," seven-time Cup series champion Jimmie Johnson said (via Autosport). "I heard some guys talk the closing rate was similar to what was run in 2001 or maybe what a truck would run like, but in my Cup career I haven't experienced either of those."
The higher speeds were a product of NASCAR's new 2019 aero package, which did away with the restrictor plates long used to limit speeds at Talladega and Daytona International Speedway. Instead, the teams used a tapered spacer. The result: Cars were producing about 100 more horsepower.
The higher RPMs also led to greater stress on engines, leading to a second NASCAR rule modification. Teams will be allowed to choose between two different rear-end gear options (.345 and .350) until qualifying Saturday. The gear they choose for qualifying will then be used for Sunday's race.