NASCAR on Thursday passed a rule that will curb the ability of teams to set their cars up in a way that gives the driver easier rear steer.

The technical bulletin issued by NASCAR goes into effect next week at Chicago, when the Chase for the Sprint Cup championship begins, and many believe it is aimed directly at powerhouse Hendrick Motorsports.

Drivers have alleged for months that Hendrick made gains in the rear housing this season that gave its cars an aerodynamic advantage. NASCAR has maintained through the complaints that the Hendrick teams weren't breaking any rules, which four-time champion Jeff Gordon reiterated.

"When we presented it to NASCAR for approval, they didn't act like it was something they had never seen before," Gordon said. "I don't even think we were the first ones to do it."

Gordon also alleged most everyone in the garage is doing the same thing now, which Kyle Busch confirmed — with a caveat.

"We all started working on it once we saw what they were doing," Busch said. "It's follow the leader. You really don't have many secrets here in the garage area very long. We started going to work on those kind of things, too, and trying to manipulate some of the same things they were doing."

Starting next week, NASCAR is limiting the amount of movement of the bushings located in the rear suspension to a quarter of an inch. The bushings are sleeves made of rubber or other materials located near the rear mounting points. Hendrick teams found a way to make them softer and softer in an effort to let the truck arms move and help steer the rear of the cars in the turns.

Brad Keselowski has been one of the most vocal critics of the development Hendrick has done, but NASCAR could do nothing.

"It's an advantage, but it's a legal advantage," Busch said. "There is nothing illegal with what they were doing."

But there will be limits starting next week, when Hendrick will have at least two and possibly all four of its drivers racing for the championship. Five-time champion Jimmie Johnson and Dale Earnhardt Jr. are already in the Chase, while Kasey Kahne and Gordon are trying to lock down wild card spots Saturday night at Richmond.

Gordon said the Hendrick cars are doing the same thing as everyone else in the garage.

"When you watch on TV and see the cars skewed, running sideways down the straightaways, it's pretty obvious what everybody is trying to do — everybody is trying to get as much downforce in the car as possible," Gordon said. "And every time NASCAR comes up with a rule, you go OK, 'How do we get around the rule?' I feel like that's what everybody is doing, and our guys have done a lot of work in that area to gain that advantage and I give them all the credit in the world."