More than 20 members of the Illawarra Mountain Bike Alliance took to the bush along a section of Harry Graham on Saturday morning to clear out tonnes of rubbish.

"These are prime dumping spots which have been abused over the years," said the event's organiser Geoff Parker.

"We're picking up anything we can move with a trolley or a trailer. So far we've collected a lot of bottles and cans - we're splitting the recycling material from the non-recyclables.

"We've picked up heaps of tyres - at least eight - as well as a TV set, desks, old suitcases - you name it - we've pretty much pulled it out," Mr Parker said. "We're just about to head onto a section that's got a bed and a TV, so we'll do our best to pull that out as well."

It was the second clean-up day the alliance had undertaken along the escarpment this month.

Three weeks ago, more than 40 people helped clean up a section of mountain bike trail near Clive Bissell Drive.

Mr Parker said the alliance wanted to see mountain biking become a legitimate sport in the escarpment and events like Saturday's clean-up showed bike riders were responsible.

The group would volunteer to maintain the mountain bike trails if they had legal access, and their presence would also help deter the epidemic of illegal dumping. "We want to show that the mountain bike community cares about the environment," he said.