IndyCar 2015 aero kits a big speed boost

Chevrolet and Honda have testing programmes under way ahead of the homologation deadline in January, with the new bodywork set to make its race debut in St Petersburg.

Both manufacturers have actively worked to maintain a high level of secrecy around their projects, although Chevrolet was the victim of leaked spy shots from a road course test at Austin last month.

Descriptions from drivers about tests have been correspondingly rare, but while Castroneves declined to discuss when or where he sampled the new kit, the Team Penske star told AUTOSPORT that his initial impressions were that the projected improved lap times will be achieved.

"I tested it on an oval once, although obviously it was just an initial [version] of the kit, and I'm sure it is going to change a lot," Castroneves said.

"Right now, the only thing I can say is that there is obviously more downforce.

"Remember, we're talking about a car that was developed three or four years ago, and when you update downforce versus drag, it's huge.

"So you are going to see some very fast speeds out there.

"It's going to be fun. It's very heavy [in the steering] - I'm going to have to work out a little bit in the arms - but that's a good thing.

"When you add more downforce, it obviously becomes heavier. But I think we'll see some faster lap times than we did this year."

Both manufacturers are expected to formally reveal their aero kits to the public shortly after the homologation process has been completed.