Cancer sufferer Kevin Osmond to cycle 140km with son Andrew in Adelaide

Thirty years ago Whanganui cyclist Andrew Osmond rode his first race with his dad, Kevin - next month the pair will ride their last.

After being diagnosed with terminal leukaemia cancer 73-year-old Kevin made the decision to enter one last race - Adelaide's Bupa Challenge Tour - and Andrew just couldn't resist flying over to join him.

The St George's principal said his dad was always there supporting his cycling and this time it was his chance to return the favour and enjoy one last ride with his old man.

"If he needs water I'll be there with the drink bottles and if he gets a puncture I'll give him my bike, fix the puncture and try catch up with him."

Andrew said it was in 1987 when he had asked his dad if he would take him and his mates up to ride around Lake Taupo and his dad had said he would do it with too.

"I laughed and said I could do it in half the time he could and he challenged me to it.

"I crossed the finish line in about 4.50 hours, and then it got to 5 hours, and no sign of dad, 6 hours, 7 hours and then at 8.20 hours dad shows up."

Since that race the pair had cycled together as often as they could.

"Dad's come a long way since that Taupo race when he had spanners and bananas taped to his bike but for a 73-year-old to do this ride is going to be tough ... I'm sure dad will go to some dark places on the ride and I'll just be there to support him through. "

The duo will take the plunge for the 140km bike on January 19.

The Bupa Challenge Tour is the Santos Tour Down Under's annual mass-participation ride that takes place a day before the pros and is in its 20th year.