Haas's Romain Grosjean worked hard and braked hard all day in Bahrain as his sampled Carbone Industrie's product in the team's quest for more consistent braking power.
Dogged with braking issues since last summer which weakened his confidence, the French driver admitted that CI's product already felt better compared to Brembo's offering despite the fact that the latter had improved greatly lately.
"We still have a lot of work to do around them and see the performance, but it feels better, as it was last year,” explained Grosjean after testing.
"Otherwise it's quite similar. We just need to see if we can actually make it work with all our mapping."
If further testing validates Carbone's brakes, Haas could switch suppliers sooner rather than later according to Grosjean.
"I think it could come for Russia. It's all ready," he said.
"But only if we're confident that we're going to start Russia without a hitch, as you cannot miss FP1 and part of FP2 because you're not right on mapping.
"We've collected a lot of data today and I think the guys are going to be working on that."
Kevin Magnussen's day tomorrow could ultimately sway a choice which is rendered more complicated by Brembo's recent improvement.
"With the Brembo we have the baseline. We know how it works. On the other one, we've worked for an afternoon but it's not a lot.
"We did seven or eight runs. The time to change the brake balance, the time to change the mapping and get it more or less where you want.
"I think Kevin is going to keep working tomorrow [Wednesday] and then we're going to decide."
GALLERY: All the action from the Day 1 in-season testing at Bahrain
Keep up to date with all the F1 news via Facebook and Twitter
Helmut Marko believes that Red Bull and Max Verstappen are unlikely to challenge for victory…
Automotive giant General Motors is reportedly back in the game as a potential entrant in…
The opening day of running at the Las Vegas GP was a smooth but chilly…
Williams is continuing to fight uphill battles this weekend in Las Vegas as a knock-on…
It was a solid start to the Las Vegas weekend for Ferrari with Carlos Sainz…
Lando Norris didn’t hold back in his assessment of McLaren’s performance on the opening day…