Unusually warm weather greeted drivers and their teams on Friday at Circuit de Spa-Francorchamps as practice began for Sunday's Belgian Grand Prix. With not a cloud in sight, sunshine bathed the 7.004-kilometer (4.352-mile), 19-turn circuit with temperatures of 26 degrees Celsius (79 degrees Fahrenheit) and 31 degrees Celsius (88 degrees Fahrenheit) for FP1 and FP2, respectively.

Haas F1 Team drivers Romain Grosjean and Esteban Gutierrez made their installation laps in FP1 using unmarked prototype tires from Pirelli. And after making their first at-speed runs on the Pirelli P Zero Yellow soft tires, with Gutierrez running six laps and Grosjean turning five laps, each driver returned to the prototype tires for some flying laps. The prototype tires are being evaluated by Pirelli for use later this season, where the design is better able to withstand contact with curbing and minimal contact with other cars.

After running on the prototype tires - Grosjean for six laps and Gutierrez for seven laps - the duo came back to the garage and returned to the Yellow softs to finish the 90-minute session. It was during this final stint that both drivers recorded their fastest FP1 times - Gutierrez with a 1:50.583 on his 17th lap that put him 10th quickest and Grosjean with a 1:50.899 on his 15th lap that put him 11th overall.

Leading the way in FP1 was the Mercedes duo of Nico Rosberg and Lewis Hamilton. Rosberg's quick time was a 1:48.348, which was .730 of a second better than Hamilton.

Haas F1 Team took a two-pronged approach to FP2, with Grosjean beginning the second 90-minute session on Pirelli P Zero White medium tires while Gutierrez stuck with the Yellow softs. Grosjean ran six laps on his first stint and Gutierrez made four laps.

For their next two runs, the drivers shared similar tire strategies. Both went out on used prototypes, with Grosjean running five laps and Gutierrez turning four laps. A switch to Pirelli P Zero Red supersofts was made for each driver's third run, with Grosjean running four laps and Gutierrez making five laps. It was during this stint when both drivers secured their fastest times. Grosjean turned a 1:49.419 on his 14th lap and Gutierrez clocked a 1:49.648 on his 11th tour.

For their final drives in FP2, Grosjean and Gutierrez differed on tire selection, with Gutierrez switching to Yellow softs while Grosjean stuck with Red supersofts. Gutierrez finished the session with a 10-lap run, while Grosjean's last stint was cut to only five laps when a problem developed with his car's motor generator unit-kinetic (MGU-K).

Atop FP2 was Red Bull's Max Verstappen, who ran the day's quickest time with a 1:48.085, which was .263 of a second better than Rosberg's fast time in FP1. Verstappen's teammate, Daniel Ricciardo, was the second-fastest driver in FP2, .256 of second behind Verstappen. Mercedes, meanwhile, was sixth and 13th quick in FP2 via the times posted by Rosberg and Hamilton, respectively.

Between the two sessions, Haas F1 Team ran a total of 82 laps - 38 by Grosjean and 44 by Gutierrez.

Romain Grosjean: "It's not been an easy day for everyone. The tires are very tricky to work. I'm not so happy with the tire pressure we have to run here. It makes things challenging. On supersofts in the afternoon, we ran better. The car felt more together, which was definitely a positive. Unfortunately, we couldn't do a long run because of an issue, but hopefully that won't cost us too much in the race. We still have tomorrow morning to prepare for qualifying, and try a few setup tricks that we're thinking of. Generally, I think all our energy will again be on tire usage."

Esteban Gutierrez: "It was very tricky conditions today. It's not common in Spa to have heat like this. The track is really hot, so we're struggling a little setting up the car. We've done some tests to try to understand it a bit better, so now we'll have a clearer direction as to where we have to focus. In both sessions we ran the Pirelli prototype tires. They were pretty transparent. There was nothing very different with them. In FP2, we also did a race simulation, which I wasn't too happy with, so we'll be analyzing all the data this evening to try and find a good setup for tomorrow and continue through the weekend."

Guenther Steiner: "In FP1 we had very similar issues with the cars, basically understeer in both, Romain probably a bit more than Esteban. We found something between FP1 and FP2. Things got a little bit better, but we still need to find a more stable balance for tomorrow. All in all, the second session was ok - nothing fantastic, nothing really bad. We just need to find more so the drivers are happy with the balance of their cars. Romain's session stopped short by a few minutes, as we saw an issue with the MGU-K. We decided to stop as a precaution and not risk breaking something. He didn't get his long run in, but we will make it up tomorrow."

Check out our Friday gallery from Spa, here.