Friday MotoGP practice in Austin saw Honda debut its version of Ducati's rear swingarm ' tyre cooler' .

HRC - along with Suzuki, KTM and Aprilia - had previously protested the device on the grounds that it was mainly for aerodynamic purposes.

However the device was confirmed as legal after evidence from Ducati showed the tyre temperature reducing by up to seven degrees in Qatar .

The Honda device has apparently been cleared on the grounds of swingarm 'stiffness', although Marc Marquez stated the difference it creates as 'downforce. It's an aerodynamic thing'.

Yamaha was the only manufacturer not involved on either side of the protest, and credited by Ducati as inspiration for the cooler due to its swingarm spray deflector for wet weather races last year.

Valentino Rossi, currently third in the world championship for Yamaha, now wants the factory to produce a tyre cooler for his M1.

"For me it's something that can be quite important for us, because it can help the rear tyre to have a little bit less temperature, like Ducati said, a little bit cooler. And it's good especially in the race," said Rossi, after being third fastest in Friday practice.

"So I push Yamaha to have something similar. Because we already have this [spray deflector] in the wet. But I hope that I can try. I don't think that this makes the difference, I think it's small things, but maybe it can be a small help."

When might he get it?

"Ah, I don't know," he shurugged. "I hope during this year, because anyway, we need to continue to work, because in the last years also, with Yamaha, we started well at the beginning of the season, but then Honda and Ducati improved, and we didn't.

"So also from this point of view, we have to try to improve test by test during the season."

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The development race is heating up as much as the track action! #AmericasGP pic.twitter.com/FCWIr9NFRf — MotoGP™ (@MotoGP) April 12, 2019

One area where Rossi knows Yamaha cannot gain much ground during the season, due to the technical rules, is closing the top speed deficit to Honda and Ducati.

"For me, anyway we work well. We are working in the right direction, and we have a good group of engineers and people around this year. But the work is long, because we lost time in the last two years. So we need time.

"The bike is not very fast in the straight, but in some other areas, we improved. So we know that the engine is closed [sealed]. So for this year, it will be like this. So with a long straight, maybe we suffer.

"But we have to work on the corners, and try to take our strong point."

While his bike might be gasping a little on the straight, Rossi himself is in better physical shape.

"I am better this year because I can train more by running," said the 40-year-old. "Because last year, I had still some pain in the leg. So I have to go with the bicycle, but I felt pain if I went running. This winter I can run because I feel good, and I am better. But also I think that the bike is improved compared to last year."

The Italian added of his 5-2 finishes so far this season:

"We found a quite good balance of the bike on Sunday morning in Qatar. And from that moment, I was not so bad. Also in Qatar I did a good race. From that moment I felt comfortable on the bike, and also in Argentina we didn't change a lot and I was not so bad. And also here.

"For me, anyway we have to work a little bit on the balance, because with the race tyres, I'm not fantastic. I have for me five riders which are faster than me. So especially Márquez and Viñales, who are stronger. But we have a good base to work on anyway, and with the soft tyre I did a good lap."

Rossi's team-mate Maverick Vinales was fastest in Friday practice at COTA, with world champion Marc Marquez second for Honda.