Joan Mir “happy” with carbon fibre swingarm, but losing “10k” on the straight

Joan Mir says Honda’s new carbon fibre swingarm delivered a small but welcome step forward during the post-race MotoGP test at Aragon.

But he warned top speed remains the RC213V’s most urgent weakness heading into this weekend’s Italian Grand Prix at Mugello.

The HRC rider joined LCR’s Johann Zarco in evaluating the new composite swingarm, which aims to improve rear grip and acceleration and, potentially, reduce chatter.

While Mir was encouraged by the early signs, he warned that high grip levels during a Monday test can distort performance.

“It’s positive, it is something that will help us to be more competitive,” Mir said. 

“I would say that is not a revolution but is a step in terms of grip. Because we are so far in terms of acceleration and grip, if we get something that improves in that area, we make a big step. This is what happened.”

“But on a Monday, the grip is always very high. So I try to be very careful with what I feel about the bike, because with good grip on track, everything looks fine.”

Nonetheless, Mir added that the swingarm gave him “nothing negative” in terms of feel and improved edge grip, with small lap time gains.

“We maintained a small improvement. Apart from that, we tried electronic things, nothing related to the engine side, so power is the same and will be the same until I don't know when,” he continued.

“But it’s now the priority to try to improve there. Like I said [during the race weekend], if we improve one of these two areas - the top speed or the acceleration - in this test, I will be happy and I'm happy because we did it.”

As Mir indicated, Honda's engine remains far behind its rivals in terms of outright speed.

Mir, who was the fastest Honda in 10th place at the Aragon test courtesy of a morning lap time, said the factory’s top speed deficit is costing him around 10km/h and several tenths every lap.

“This morning, I was riding with the medium tyre and did '46.4 with 8 or 9 laps on the tyre, so it was impressive,” he said.

“But the truth is that we lose 10k per hour on the straight. So imagine, that is two or three tenths more we could get for free… Not free for Honda, but free for me!”

The three RCV riders - Mir, Zarco and Somkiat Chantra - were left at the bottom of the speed charts in both Sessions at the Aragon test.

On paper, that speed gap should be brutally exposed again this weekend at Mugello, the fastest straight of the MotoGP season.

“It was very difficult to manage because in the race, sometimes you follow somebody and then somebody follows you. So you cannot overtake, and the one behind will overtake you!” he said.

However, the fast final corner gives Mir some hope.

“At Mugello, you start [the straight] from third gear. So maybe in that area it won’t be so bad. We will see.”

Mir’s team-mate Luca Marini remains sidelined by multiple injuries sustained while testing a Superbike in Japan.