Red Bull first issue with Honda is overcoming vibrations causing rear end instability, reports have cited Sky Sports contributor Marc Priestley as saying.

During the winter, it was confirmed by the team that the Japanese manufacturer hadn't been able to test their new engine at full power because of vibrations on the dyno. however, a full assessment wasn't possible until the car hit the track.

Well, despite two trouble-free days of running in Barcelona completing over 200 laps, it would appear the new partnership still has some small creases to iron out.

"The problem is not so much the engine but the complete rear," a separate source told GPToday.com. "That is not yet in balance and therefore it doesn't run as they want at Red Bull Racing."

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While vibrations at low-revs are usually not an issue, if strong shaking does continue higher up the rev range that is when it can have a major impact on the car's performance.

Red Bull hasn't commented on the rumours, but it will be a story to follow as testing continues and teams start extracting more performance from their 2019 cars.