Lando Norris has admitted that McLaren's brake problems have set the team back "a lot of laps" in their quest to get on top of their 2022 car.
McLaren are yet to confirm exactly what problem they encountered with their brakes, with Norris suggesting that it centred around brake temperatures in the hot Bahrain conditions, preventing the team from doing longer runs.
It was a frustrating day for all at McLaren, having also been forced to make a last-minute driver change in Bahrain.
After Daniel Ricciardo fell unwell, Norris stepped in at the final moment to pilot the car. The team hope that Ricciardo will be back behind the wheel on Friday.
Norris ended the day fifth in the standings in terms of one-lap pace, over a second behind timesheet-topper Pierre Gasly.
Norris brands Thursday a tough day for McLaren
McLaren completed only 50 laps during day one of testing in Sakhir, just three laps more than a Haas car that missed the first four hours of the day due to a cargo delivery issue.
Six of the grid's 10 cars completed more than double that number, leaving the Woking-based team with plenty of work to do to catch up.
"I think on the whole, not the day we really wanted," Norris said after his day behind the wheel.
"I guess it started off with me doing a whole day [as] Daniel's not feeling so well. I decided to jump in [as it was] much easier to do it that way.
"But we had quite a few issues today with the car that took a long time to figure out, and it limited us quite a bit to do the amount of laps we wanted to do. [It was a] bit frustrating because, especially here being so different to Barcelona, we really wanted to try and understand as much as we could.
"[Also] the differences and how the car is working here on a much bumpier track, which I think we still did to a certain extent. We just couldn't do any of the longer running, so we made the most of it, but definitely [we had] some issues that held us back.
"[It was] brake temperatures and stuff that didn't allow us to do long runs – things we are trying to fix for the next few days. They're not going to be an easy fix, but we'll see what we can do."
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