Nicky Hayden says he suffered a nightmare race two at Aragon with mechanical gremlins which ultimately forced him to pull out to record his second retirement of the year.

The Honda Racing rider claimed a solid but unspectacular sixth place in Saturday's opening race in Spain but his plans on improvements in race two were effectively ended before lights out as he struggled with issues on the sighting lap to the grid.

The American rider says despite late attempts to rectify the front-end chatter and braking concerns by the Ten Kate squad he still had the same ill-feeling from his CBR1000RR SP on the warm-up lap.

After making a bright start to the race the 2006 MotoGP World champion says the vibrations got worse as he struggled with braking which forced him to retire to avoid any undue risks of crashing.

"It was a bad day; there is not much else to say," Hayden said. "Everything that could have gone wrong did go wrong. On the sighting lap we started having some problems and on the warm up lap, again, I could feel something was still not right.

"We had a big vibration at the front end and I could not get my bike stopped. I tried to stay out to salvage some points but there was not much I could do. Eventually it got worse, so I chose not to take any unnecessary risks and pulled out of the race.

"It's the second DNF of the season, which prevented me from getting more experience on the bike, but it is what it is. We have learned something today and we now look forward to the next round."

Hayden will be keen to battle back in two weeks time at his new team's home round at Assen after slipping to eighth in the World Superbike riders' standings.