Former 250cc World Championship runner-up Shinya Nakano has announced his retirement from racing.

"I think it's time to stop and I have decided to retire," said the 32-year-old. "Thanks to everyone who has supported me during 13 years as a professional racer and eleven years in the world championships.

"Now, if my experience is a little help, I want to contribute to the motorcycle industry. I look forward to seeing everyone at the track in the near future, this time in a different capacity."

Although he spent 2009 in the World Superbike Championship with Aprilia, Nakano is best known for his ten full seasons in grand prix racing - two in 250cc and then eight in 500cc/MotoGP.

Nakano finished second on his grand prix debut as a wild-card in the 1998 250cc Japanese Grand Prix, propelling him into a full time ride for Herve Poncharal's Chesterfield Yamaha Tech 3 team the following season.

The #56 won his second race for the team, again at home in Japan, while four further podiums pushed him to fourth in the 1999 standings. Shinya then continued his sharp upward trajectory the following season, when he won five races and took twelve podiums - but lost the world title to team-mate Olivier Jacque just metres from the finish at Philip Island.

Tech 3, Jacque and Nakano all graduated to 500cc with Yamaha for 2001 and Nakano claimed the first of just three premier-class podiums with third position at round nine in Germany, on his way to an excellent fifth in his rookie season (ten places ahead of Jacque). It would be by far Nakano's highest ranking in 500cc/MotoGP.

Nakano looked to have a brilliant future ahead of him, but the arrival of the new four-stroke era saw Tech 3's two-strokes outgunned for much of the 2002 season. The team were handed YZR-M1s for the last three rounds, but Yamaha's first four-stroke was no match for Honda's RC211V and Nakano finished the season eleventh in the standings, a best of fifth on the 500 and sixth on the M1.

The arrival of Alex Barros at Tech 3 for 2003 saw Nakano shift to the d'Antin Yamaha team, but he was unable to better fifth position on the pre-Valentino Rossi version M1, and took tenth in the championship.

Nevertheless, his continued efforts caught the attention of Kawasaki, which tempted the Japanese with the chance to be a full factory rider for the first time in MotoGP, albeit on the least competitive factory machine.

Inspired by the responsibility, Nakano absorbed himself in trying to move the ZX-RR project forward - and claimed an emotional podium finish with third place at his and Kawasaki's home grand prix in Motegi.

Prior to the podium, Nakano had suffered a huge 200mph accident at Mugello when his rear tyre failed along the home straight - and proved there was a steely resolve behind his polite exterior by claiming seventh place just one week later at Catalunya.

Hopes were high that Team Green could build on its momentum in 2005, but the project seemed to have peaked and while Nakano claimed his third tenth-place championship ranking in a row, this time he was without a podium.

Nakano benefitted from Colin Edwards' last turn accident at Assen 2006 to claim MotoGP best second place, but unreliable machinery meant he was only 14th in the final championship standings. Kawasaki did all it could to convince Nakano to stay for 2007, but uncertainly over its new 800cc motorcycle - combined with the expected chance to fight for race wins on a Michelin-shod Konica Minolta Honda - tipped the balance in favour of pastures new.

Most riders would have done exactly the same, but the decision proved to be a nightmare: The new RC212V was uncompetitive (and remained that way for the non-factory riders) while Michelin lost its 'grip' in the battle for tyre supremacy with Bridgestone.

Nakano finished the year just 17th in the standings, with a best finish of tenth, but Honda believed he deserved a second chance and placed him back on Bridgestone tyres at the Gresini Honda team for 2008.

Shinya made a modest start to his Gresini career, with a best finish of eighth heading into round twelve at Brno, where he was surprisingly rewarded with a (valve-spring) factory Honda ride. HRC claimed that the move was down to his consistency (points at every round), experience and language - since he would be developing next year's satellite bike.

Few were convinced by that explanation - and Dani Pedrosa's subsequent switch to Bridgestone tyres seemed to indicate the real reason - but Nakano silenced the doubters by charging from twelfth to fourth on his factory RCV debut in the Czech Republic.

The final six races yielded a best finish of fifth, but Nakano knew that his Gresini seat was lost three rounds from the end of the season, when Toni Elias was confirmed alongside Alex de Angelis for 2009.

Nakano was tipped to become a Honda test rider, but was thrown a potential MotoGP lifeline when Kawasaki began pushing for their former rider to steer a possible third ZX-RR, to be run by 125 and 250cc team manager Jorge Martinez 'Aspar' next season.

Unfortunately for Nakano, Aspar wanted a Spanish rider to please his sponsors and the whole project eventually broke down, ending Nakano's final hope of remaining on the premier-class grid.

A place as a test rider for any of the Japanese teams would have been possible, but Nakano believed he had plenty of racing potential left and chose to take on a new challenge in the World Superbike Championship - riding Aprilia's brand new RSV4 alongside Max Biaggi in 2009.

A fourth place during round two at Qatar indicated a potentially promising partnership, but Nakano broke his collarbone next time out at Valencia and also missed the following Assen round.

After his comeback, Nakano went on to claim a best of sixth place at Donington Park (round nine), before a neck injury during round eleven at the Nurburgring forced him to sit out the remaining three rounds and ultimately marked the end of his professional racing career.

Team-mate Biaggi took nine podiums, including one race win, on his way to fourth in the 2009 WSBK championship.