LeBron James is notorious for tinkering with his free throw form, last season going through at least 18 different routines. It’s all in his quest to shoot 80 percent from the line for the season, which he described as “my last goal of my NBA career” before this season. Alas, he didn’t quite get there, shooting 73.1 percent during the regular season.

James’s latest routine, however, has drawn some attention because of the fact that it appears to be illegal.

Here’s a clip from Sunday, when the Cleveland Cavaliers eliminated the Indiana Pacers in Game 7 of their first-round playoff series.

James clearly steps over the free throw line before the ball hits the rim, a violation of NBA Rule 10, Section 1(d): “The free throw shooter may not cross the plane of the free throw line until the ball touches the basket ring, backboard, or the free throw ends.”

But John Goble, a referee during Cleveland’s second-round opener against Toronto on Tuesday night, wasn’t having it in the third quarter as James attempted his sixth and final free throw of the game.

James scored 26 points Tuesday night but made only 1 of 6 free throws (the other Cavs made 14 of 15 in a one-point overtime victory). It was a big step down from Cleveland’s first-round series, when he shot 81.8 percent against the Pacers. Indiana’s fans were, shall we say, perplexed that the refs only started whistling James for a violation after their seven-game first-round series was over.

Read more on the NBA from The Post: