The coroner has highlighted safety issues with tubed tyres in his report into the death of a motorcyclist in 2012 .
On July 20, 2012, Bryan Wyness, 71, a retired businessman living in Pukekohe, was riding his BMW motorcycle on State Highway 1 when he was killed in a crash at Rangiriri, in the northern Waikato.
Wyness was riding the same BMW F 650GS touring bike that had carried him across central Asia during the famed travels of the "Silk Riders" in 2005.
In a report released today, Coroner Gordon Matenga said Wyness was riding in the left of two southbound lanes travelling towards Hamilton and police had said Wyness was travelling slowly at the time of the crash.
A driver of a car behind Wyness pulled out to overtake him, but at the same time the motorcycle began to drift from the left lane into the right lane, its handlebars began to wobble and Wyness lost control.
The bike and its rider fell and slid into the median barrier. Wyness suffered multiple injuries including a fatal spinal injury, the coroner said.
There was no collision between the motorcycle and the car, and "no evidence of a precipitating medical event".
The crash is believed to have been caused by a slow air leak from the front tyre, which, upon reaching a critical point, caused the tyre walls to collapse and sudden loss of all remaining pressure in the tyre.
It was discovered that the front tyre tube was as old as the eight-year-old motorcycle and "may well have been the original".
The report found tubes expanded over time due to "ordinary use". In this case, the expanded tube chafed against the tyre, resulting in the leak, and ultimately the tyre's sudden deflation and Wyness's loss of control.
Matenga ruled the death was "accidental".
However, he recommended that a copy of the findings be sent to the New Zealand Transport Agency and ACC, and that all those who rode motorcycles in New Zealand were warned to be aware of tyre manufacturers' recommendations - if a tyre is replaced then the tube should also be replaced.
"This inquest has highlighted an important safety issue for those who ride motorcycles with tubed tyres," Matenga said.
"The evidence I have ... is that in Germany, America and England, if a tyre is changed on a wheel that has a tube, then the tube must also be changed.
"The tyre manufacturers, Pirelli, have it written on the tyre in German. I am advised that it translates as, "New tyre, new tube."
The coroner said this did not reflect the law in New Zealand. Motorcycle tyre mechanics were able to reuse the old tube when replacing worn tyres and this was "clearly a concern".
Wyness was one of six "Silk Riders" - a group that included high-profile economist Gareth Morgan - that rode the three-month, nearly 20,000-kilometre Silk Road trip from Venice to Beijing, in 2005 following the footsteps of 13th century trader and explorer Marco Polo.
The tour received widespread publicity with Morgan and his wife Jo writing a book – Silk Riders – about their travels.
Wyness had a passion for motorsport, owning three motorbikes and four Jaguar cars.