LE CASTELLET, France — Valtteri Bottas topped the leaderboard ahead of Mercedes teammate Lewis Hamilton in the second practice for the French Grand Prix on Friday.

Bottas was .424 seconds quicker than Hamilton, reversing their positions from the first practice, while Charles Leclerc was third fastest ahead of his Ferrari teammate Sebastian Vettel.

Championship leader Hamilton made a rare mistake in the second session when his left rear tire slid going into a turn and he clipped one of the bollards, sending him momentarily off track. Max Verstappen was just behind him and briefly slid off.

Although the Red Bull driver did not appear to be impeded by Hamilton, stewards investigated the incident before deciding to take no action against either driver.

"Both drivers agreed that the limited rear visibility and the angle of Car 44 (Hamilton's) made it difficult for Hamilton to see the approaching car (Verstappen's) and agreed that Hamilton rejoined slowly," the stewards concluded in a statement. "The stewards could observe from the on-board video that Hamilton looked in his mirrors at least twice before attempting to rejoin the circuit."

Montreal's Lance Stroll was 18th in the 20-car field.

Mercedes has won all seven races this season — five wins for Hamilton and two for Bottas — and again looked stronger than Ferrari.

"All the tires are gone," Leclerc moaned over the team radio near the end of the session as he struggled on the soft tire compound.

Hamilton also expressed some concern at the start, saying his front tires were not balanced properly.

Mid-afternoon temperatures hit 55 degree Celsius (131 Fahrenheit) on the Circuit Paul Ricard in southeastern France, and despite a bone-dry track several drivers still struggled with tire grip.

Vettel had a moment in P2 when he went too wide but regained control of his car, while French driver Romain Grosjean's Haas car kept slipping around the 5.8-kilometre (3.6-mile) track.

"I can't have a car that's (only) good over the first five corners," lamented Grosjean, who has scored only two points.

There is a final practice on Saturday ahead of qualifying.

Earlier Friday, Hamilton was .069 seconds quicker than Bottas.

Ferrari again struggled with their tire set ups in P1, but Leclerc found some form toward the end to clock the third-fastest time. Vettel, who has not won in 15 races dating to the Belgian GP last August, was fifth behind Verstappen on a frustrating day.

Vettel already trails Hamilton by 62 points and has two second-place finishes so far.

Hamilton, who is chasing a sixth world title, has won the last three races and leads Bottas by 29 points overall.

The French GP is the eighth of 21 races this season.


More AP auto racing: https://apnews.com/apf-AutoRacing and https://twitter.com/AP_Sports