The Haas Formula 1 team has decided to revert to Brembo brakes for the remainder of the Russian Grand Prix weekend, following its test with Carbone Industrie in practice.
Haas has been experimenting with brake materials in a bid to make improvements in an area it has struggled with since joining F1 last season, and ran CI products in last week's Bahrain test and in Friday practice at Sochi.
Although those tests have been encouraging, issues with cooling of the new discs has prompted the team to elect to take make more time before committing to them for a full race weekend.
Team principal Gunther Steiner said pre-weekend he hoped to remain on the new brakes throughout the event, but the team decided to go back to Brembo on Friday night.
"We are still not completely on top of how to manage the brakes, and therefore it was a test session for us," he said before that change.
"You saw the brake dust coming out when braking - but we knew that after the Bahrain [test] and we are working to have more cooling options.
"In parallel we are developing more cooling options for the brakes, so we will be fine. It just takes a little bit of time to get used to them."
Haas plans further windtunnel tests to get on top of the brake cooling requirements next week.
Romain Grosjean has regularly complained about the feel of the brakes and faced difficulties again on Friday in Russia, including a spin in FP2.
"The car balance wasn't great," said the Frenchman. "I wasn't happy all day long with it, we had some issues with the brake as well on the long run, with the brake pedal going [long] I think we can sort that out, we've got some ideas, but generally the car didn't perform at all.
"But Formula 1 is all about finding the last fine-tuning. We got better recently, we were very happy with Carbone Industrie in Bahrain, but here we're struggling a bit more.