Like I have been saying all along, the Gen 4's were the worst AERO car they made. Don't take my word for it, read what Earnhardt says.
GEN 4
But Gen 4 cars were as aerodynamically sensitive as any prototype sports car ever fielded at Le Mans. One little bump on a fender and a driver's day was done. Earnhardt used to say that if he could clone himself and race against himself in an old Monte Carlo from the 1970s versus a new Monte Carlo, he'd win in the old one every time. He would beat on the new one and "rough it up" until it became aerodynamically dysfunctional, while the tougher old one motored on.
In distorted retrospect, some fans think they had brand identification in Gen 4. All I know is, without the logos and a micrometer, you couldn't tell one make from another.
GEN 5
The COT, now filed away in history under the less painful term Gen 5, was vastly safer -- wider, roomier, with cocoon-like survival cells as seats -- than anything before. And it was much tougher than the prissy Gen 4 de facto prototypes. In a throwback to Gen 2, drivers could slam and bang and keep on trucking, even at Daytona and Talladega, with the thick-skinned COT.
With the COT, the spectacular could be safe -- drivers walked away from the "big ones" at Daytona and Talladega, emboldening them to risk more spectacular wrecks, such as
Kyle Busch's wild ride as he narrowly lost to Tony Stewart at Daytona in July of 2009.
http://espn.go.com/racing/nascar/cu...car-gen-6-cars-us-look-back-previous-cup-cars