CHARLOTTE, N.C. — NASCAR’s latest attempt to reel in the rule-breakers aimed at an unfamiliar target: the normally squeaky-clean Joe Gibbs Racing.

NASCAR’s decision Wednesday to suspend seven JGR crew members indefinitely for attempting to manipulate a horsepower test after a Nationwide Series race last weekend put a serious dent in owner Joe Gibbs’ reputation

While NASCAR decided against banning the cars from future races, the penalties were among the harshest NASCAR has levied.

— Crew chiefs Jason Ratcliff and Dave Rogers were suspended and fined $50,000 each.

— No. 18 car chief Dorian Thorsen, engine tuner Michael Johnson and crew member Toby Bigelow and No. 20 car chief Richard Bray and engine tuner Dan Bajek all were suspended indefinitely.

— Drivers Tony Stewart and Joey Logano were each docked 150 driver points. JGR was stripped of 150 owner points for each car, and the teams were placed on probation for the rest of the season.

“In this particular case, the rule violation was serious and was attempting to interfere with our ability to conduct an accurate post-race competitive analysis,” NASCAR spokesman Kerry Tharp said. “It called for a serious reaction on our part and we think the penalty speaks to that.”

Gibbs, the former Washington Redskins coach, indicated he would not appeal the major penalties. Gibbs said he’ll even impose additional fines, and all the crew members involved would be suspended at least through the end of the season.

“In 17 years we have never had any representative of Joe Gibbs Racing knowingly act outside of NASCAR’s rules, and that is something we consider essential to how we operate on a daily basis,” Gibbs said in a statement. “What we have determined is that these individuals involved used extremely poor judgment.”

After Stewart finished third in Saturday’s race at Michigan International Speedway in the No. 20 car and Logano was seventh in the No. 18, inspectors found magnets on the gas pedals on both cars when they were sent to the chassis dyno for examination. NASCAR vice president of competition Robin Pemberton said the teams were attempting to mask the cars’ true horsepower

“I would like to apologize to the employees and partners of Joe Gibbs Racing,” Ratcliff said in a statement. “Because of poor decision making, I have failed you as the leader of this team and I am solely responsible for this situation. Secondly, I apologize to the men and women of NASCAR for my dishonesty and interference during a testing event.”

The discovery of magnets in an attempt to make the test show the cars were using less horsepower came as Gibbs’ No. 18 and No. 20 Toyotas have dominated NASCAR’s second-tier series. They’ve combined to win 14 of 25 Nationwide races, and NASCAR last month ordered all Toyota teams to cut about 15 horsepower in their motors.

The No. 20 car’s lead in the owners standing was cut to 168 over the No. 2 car owned by Richard Childress Racing.

“I accept the penalties imposed by NASCAR and Joe Gibbs Racing and make no excuses,” Rogers said.

The penalties continue a NASCAR trend to take a stronger stance on cheating.

NASCAR took away 150 driver points from Martin Truex Jr., and crew chief Kevin “Bono” Manion was fined $100,000 and suspended six races for bringing an illegal car to Daytona in July.

NASCAR on Wednesday also fined Sprint Cup driver Reed Sorenson’s crew chief Donnie Wingo $25,000 after the car was found to have an improperly attached weight in Sunday’s race at Michigan.

While NASCAR has increased the penalties, JGR had rarely come under scrutiny from NASCAR. Before last weekend, the last time a JGR car came under suspicion was in 2003 when Stewart’s car was impounded after failing inspection before it hit the track at Texas Motor Speedway.

The point deductions Wednesday mean little to Stewart, who was racing in his final Nationwide race for JGR, and Logano, who has run a partial schedule since turning 18 earlier this year. Gibbs said he didn’t agree with placing the drivers on probation, claiming they had no knowledge of the cheating.

Wally Brown will serve as Logano’s crew chief Friday in the No. 20 at Bristol Motor Speedway, while Doug Hewitt will be the No. 18 crew chief with Kyle Busch as the driver. JGR was busy Wednesday night assigning new duties to other crew members.

And while the penalties come in the Nationwide Series and not the top series, Sprint Cup, NASCAR officials are hoping they’ll make another crew member think twice when they’re considering tweaking the car.

“A poor decision was made by some key members of our organization,” Gibbs said. “And 100 percent of the blame rests with us.”