Haas are undecided whether to switch their brake supplier from Carbon Industries to Brembo after seeing a recent improvement.
Romain Grosjean has been particularly critical of the Carbon Industries brakes and tested new Brembo brakes at the two-day test in Bahrain.
But the switch will not be made for Russian Grand Prix as the Frenchman revealed that the team have finally seen a positive response from their current suppliers.
"They feel very similar," said Grosjean to Auto Motor und Sport.
"But we can see from the telemetry that a few things are already working better. They behave more in the way I like at the end of the braking process.
"But there was an update in China and since then it [the Carbon Industries brakes] has worked better. We had to wait a year and a half to get it.
"We should be completely sure that we are improving [before changing].
"We cannot sacrifice practice sessions to continue working on brakes."
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