Completing that gave him the idea of doing the ride from Taupo which is a similar distance.
While he knows it's going to be a hard days work, he's determined to finish.
"I'd be lying if I said it's going to be fun riding for that long. I'll be physically sick and probably collapse afterwards but I'm expecting that," he said.
He's going to be filling up on carbohydrates in preparation for the ride and wife Karen will be waiting every 50-60km to top up the water in his camelbak. Having done the Lake Taupo cycle challenge annually since 2001, Mr Leishman is no stranger to cycling - he says he's well aware of the need for a good tail wind.
"A tail wind would be great but any wind in my face would be terrible.
"Rain is not so bad but if there's a strong headwind, I'll have to postpone."
With his pink 'cancer sucks' socks and Relay for Life bike ribbon, he'll be hard to miss.
To get behind David's fundraising effort, visit www.fundraiseonline.co.nz/DavidLeishman.