Ben Spies has revealed that a 'broken swingarm' was to blame for his accident in Sunday's US MotoGP at Laguna Seca.

Riding with an injured heel after a heavy qualifying fall, the Texan held fourth place for much of the race - despite near constant pressure from Tech 3 Yamaha riders Andrea Dovizioso and Cal Crutchlow - until he was flicked off his Factory Yamaha on the exit of the Corkscrew with ten laps to go (pictured).

The swingarm was clearly collapsed after the accident and Spies has now confirmed that it was the reason for his fall - rather than being damaged in the aftermath.

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Spies wrote on Twitter (@BenSpies11): "Sorry for the boys had a solid 4th wrapped up till the swingarm decided to break... When it rains it pours!"

The #11 later gave further details: "I was feeling really good, I didn't have the grip that I had in the earlier sessions with the harder tyre but in the last ten laps I was starting to pull away and I had a little left up my sleeve.

"We started to stretch out a lead over Dovi then all of a sudden at the bottom of the corkscrew the bike went out from underneath me. I had no control, it didn't slide or anything just completely went.

"At first I thought I'd hit a bump but there isn't one there. It's nobody's fault but it's more bad luck."

Fourth would have matched Spies' best result of a season littered with race day incidents. Spies, just tenth in the championship, will leave Yamaha at the end of this year.

"Ben was riding very well today and was pulling away from Dovi when he crashed. This is another part of his bad season, hopefully from Indy onwards we won't have any more bad luck," said team director Massimo Meregalli.