Garry Rogers Motorsport driver Nathan Herne says that the controversial rear windscreens on their Trans Am cars are about mind games rather than performance.

As first reported by Speedcafe.com, Turtle Wax Trans Am Series category management is now investigating the droop which all three of GRM’s Ford Mustang-bodied cars have come to exhibit.

The deformity in the rear windscreen and the back end of the roof panel is thought to lead to an increase in rear downforce, given more air will flow over the rear wing.

It is trick which NASCAR teams have been penalised for in recent years.

However, the trait is not visible in photographs of other Mustangs in the National Trans Am Series field, including vehicles of different generations.

Whether the condition of the GRM cars represents a breach of regulations remains to be seen.

Queried about the matter in this week’s episode of The Driver’s Seat podcast, Herne conceded that it is likely to achieve a performance advantage but is motivated more so by “mess[ing] with the other competitors’ heads.”

That is despite it only coming to prominence in the days since last weekend’s Queensland Raceway round.

Herne claims that his team has been aware of the issue since at least as far back as debrief after Round 1 of the season at Symmons Plains.

According to him, it was team-mate Lochie Dalton’s car which first came to have the droop at speed, due to roof strut damage, which squares which a theory from a Speedcafe.com source.

Since then, the deformity has somehow spread to the other three cars, which Herne has implied is due to leaving the roof struts loose.

“Lochie Dalton’s car was formerly [team-mate] Owen Kelly’s car, which was one of the first dozen cars in the country,” he noted.

“That actually broke one of the struts in the roof, which sucked the roof down and we noticed that in onboard footage and thought ‘gee, wonder what is going on there’.

“So that was that car, that happened at Symmons Plains. After Symmons Plains we went on top of the car and we were pushing on it and when we were cleaning the car the roof sucked in – we thought, ‘here we go, there’s something there’.

“We looked inside the car, we saw the roof strut was broken… the roof struts are literally just a small little bolt and the roof was flimsy as flimsy.

“At the end of the day, there’s no rules broken at all from GRM’s perspective, it is what it is.

“Yep, it doesn’t look good. We have done it since Phillip Island and it’s never been a problem. It has been brought up in the category before, technical delegates have never had a problem with it.”

He added later, “If the rule gets changed for next round, we’ll tighten the roof struts and that’s it; we’ll be done with it.”

Herne suggested rival Jon McCorkindale raised the matter on social media because “he had a bit of a rough weekend”.

Despite his comments suggesting the droop is intentional, he claimed that it is barely performance-enhancing.

It is, however, gamesmanship at the very least, according to the Lismore driver.

“It’s Trans Am, not NASCAR, it’s not like we’re racing around Daytona,” Herne added.

“Granted it may give us maybe half a kilometre an hour down the straight at a maximum, to be honest, and with rear aero you honestly don’t know if it helps or it doesn’t.

“It’s sort of something to mess with the other competitors’ heads and just a bit of a show to say we’re looking at everything on these cars.”