A teenage daredevil was going just 3km/h too slow when he hit a launch ramp during practise for a world-record motocross jump.
That small difference was enough to kill him, a NSW coronial inquest has found.
Tyrone Gilks, 19, came up tragically short of the landing strip at the Maitland Showground, near Newcastle, on a hot morning in March 2013.
His 250cc Yamaha slammed into the lip of the ramp, crushing his chest against the handlebars and sending his limp body tumbling for 18 metres.
The impact ruptured a major artery in his chest and his life support was switched off eight hours later.
Handing down findings on Thursday, Coroner Michael Barnes said the death was the tragic result of overconfidence and the failure to apply systematic, scientific planning.
"There was too much reliance on a trial and error approach in a context where error could and sadly did prove fatal," he told Newcastle Local Court.
On the day he died, Mr Gilks, an experienced rider and holder of several junior jump records, was planning to attempt the 94.5-metre world record.
His team set up the take-off and landing ramps in the morning, incrementally increasing the distance between them and monitoring his speed.
With the ramps some 80 metres apart, Mr Gilks's sister and others in his entourage told him he wasn't hitting the ramp fast enough.
"It is apparent that Mr Gilks does not share their concern," Mr Barnes said.
At about 10.40am, with the ramps some 80m apart, Mr Gilks crashed at 111km/h hour.
He needed to be at 114.5km/h.
Mr Barnes said the reason for the lack of speed was unclear, but could have been caused by under-revving, a last-minute signal to pull out, a fear of over-jumping, or an insufficient run-up.
It's also possible that a man walking his dog had gotten in the way, causing Mr Gilks to lose speed on approach.
He criticised the lack of risk management, including insufficient speed-monitoring, the failure to apply proper, mathematical calculations, and an approach path that wasn't properly paved.
"No reputable commercial undertaking would engage in such a high-risk activity without a formal, documented risk assessment and risk management plan," Mr Barnes said.
He recommended in future such attempts be held to stricter safety standards.
