Justin Bieber auctioning motorcycle for charity

Justin Bieber has shown off his charitable side by auctioning off his customised motorcycle for charity.

The singer is offering up his purple two-seat, three-wheeled Campagna T-Rex, which features his initials JB painted on the hood.

Proceeds will benefit professional skateboarder Rob Dyrdek's foundation, which aims to develop and construct legal skate parks.

The motorcycle is estimated to fetch $50,000 when the Charity Buzz auction wraps up later this month (Oct11).