MONTMELÓ, Spain — Veteran Kimi Raikkonen set the fastest time on the second day of Formula One preseason testing on Thursday, but Mercedes still garnered more attention by introducing an innovative wheel adjustment system.

On-board footage showed defending champion Lewis Hamilton pulling the steering wheel back and forth on the front straight to apparently change the angle of the front wheels on his Mercedes car.

The team stayed tight-lipped about the car's new feature but guaranteed it was “safe” and “legal.”

“I probably won’t shed a great deal more light than what you saw on the TV but yeah we have a system in the car, it's a novel idea," team technical director James Allison told F1 TV. ”We've got a name for it, it’s called DAS, if you're interested, and it just introduces an extra dimension for the steering, for the driver, which we hope will be useful during the year. But precisely how we use it and why we use it, that's something we will keep to ourselves."

Allison said governing body FIA knew in advance that the team was introducing the new system.

“It's something we've been talking to them (about) for some time,” he said. “The rules are pretty clear about what's permitted on steering systems and we're pretty confident that it matches those requirements. I'm pleased we got it on the car, it seems to be useful, and we'll see over the coming days how it benefits us.”

Hamilton said he was still trying to get used to the system, but praised the team for coming up with the innovation.

"I've only had one morning on (it, so) I don't really have a lot to talk about with it. We're trying to get on top of it, understand it, but safety-wise no problem today and the FIA are OK with the project.

“For me it’s really encouraging to see that my team is continuing to innovate and stay ahead of the game, and I think that’s down to the great minds in the team and so hopefully that’ll work to our benefit."

Hamilton led the time charts on Wednesday but was only ninth-fastest on Thursday.

The 40-year-old Raikkonen, who has a chance this season to break the record for most race starts in F1, was fastest with a time of 1 minute, 17.091 seconds in his Alfa Romea. He was 0.2 seconds quicker than Sergio Pérez with Racing Point. Daniel Ricciardo of Renault was third.

Raikkonen caused a red flag near the end of the afternoon session when his car stopped on the track with an apparent mechanical issue. The Finnish driver had spun earlier in the session, as did Valtteri Bottas of Mercedes, Romain Grosjean of Haas and Pierre Gasly of Alpha Tauri, formerly known as Toro Rosso.

Grosjean had the most laps among the 13 drivers who went to the track on Thursday, with 158.

Bottas was the slowest driver of the day, while Sebastian Vettel was sixth-fastest with Ferrari.

Pérez had set the quickest time in the morning session. The Mexican driver had been third fastest on Wednesday, behind Hamilton and Bottas.

Drivers will be back on the track on Friday to close out the first week of testing. Teams will have another three days to test next week.

Preseason testing has been reduced from eight to six days to help compensate for the record 22 races on the calendar, including a new Vietnam Grand Prix and the return of the Dutch GP. Midseason testing also has been eliminated.

The season opens on March 15 at the Australian GP.

The Barcelona-Catalunya track will host the Spanish GP on May 10.

___

More AP racing: https://www.racing.ap.org