American Superbike champion Josh Herrin has been dropped by the AirAsia Caterham team and replaced by Ratthapark Wilairot.

Rookie Herrin has struggled to match the podium and pole pace of team-mate Johann Zarco, failing to score a point in his ten grand prix starts.

"We have decided to replace Josh with Ratthapark. It was not an easy decision but it was necessary in order to try to bring better results on that side of the garage," said team manager Johan Stigefelt.



"We are here to be competitive with two riders and the expectations were made clear from the start of the season. Unfortunately these goals have not been met, despite our best efforts and support to Josh.



"We wish Josh all the best for the future and at the same time welcome Ratthapark to our team. I am happy that Ratthapark is joining us as we know he has the ability to battle for the points and can help us to gain good results, so let's now see how we can improve for the final six races of the season."

Thai rider Wilairot competed in Moto2 until midway through the 2013 season, with a best finish of fourth place at Assen in 2010, before announcing his immediate retirement - only to return to international competition in 2014 as part of the Core PTR Honda team in the World Supersport Championship.

Wilairot then made a GP return when he was called up to replace the injured Herrin at Jerez, finishing 19th.

"Firstly I have to say thank you very much to Tony Fernandes, Mia Sharizman, Johan Stigefelt and AirAsia for giving me this big present to ride in Moto2 until the end of the season. Also I want to thank CORE and PTR who have allowed me to do my favourite career," said Wilairot, who 'retired' from grand prix midway through last year, then moved to WSS.



"I am feeling fresh and excited to get back into the Moto2 garage, especially with the AirAsia Caterham Moto Racing Team. I made one race at Jerez already this year with them and I really enjoyed it! All the people in the team are working hard and helped me a lot with everything; it's like a big family.



"I hope to repay them for this opportunity by doing a good job and achieving positive results for the remaining six races. In Jerez we worked well together and gained valuable information for set up with the Caterham Suter bike, so I am confident that we can build on this.

"My target is to score points and finish in the top fifteen. I will open the gas and get near to the top guys."