However, starting at the back of the 12-rider 1500m final with a handicap, the pair chose to compete and play duck 'n dive with each other, which got them no closer to the leaders with half of the six laps gone.
Maxyna Cottam was first off the rank and would swap the lead with Stewart's father John Stewart.
Just behind them the middle group almost immediately came together and drafted off each other to keep their speed up, well away from the youngsters at the back.
John Stewart then took the key advantage, followed by Jeremy Cottam - Maxyna's father - and Richard Horn.
Finally putting some cohesion together, Castle and Campbell Stewart began eating up the track to catch the rest but as they rounded the turn for the final lap, they had left a lot to do.
Stewart put the hammer down and was motoring through the field by the third turn, but another promising Palmerston North rider, Carne Groube, had already made his move and could not be caught, with fellow Palmerston North rider Cody Simpson finishing second and Stewart making it up to third.
Having attended the Elite & Under 19 track nationals two weeks ago, Groube took a gap week from competing before the Wheel Race and was naturally delighted with his surprise win.
"To have watched the River City Wheel Race in the past, and to see some of the elite of New Zealand cycling win it ... it's a big honour," he said.
"A couple of us had a team talk to work out some tactics. We knew Jordan Castle was strong, and wanted one of us to take him down."
Groube will now look ahead to the Age Group & U19 Omnium Track National Championships in Cambridge in March.
Adding a historic title like the Wheel Race to his resume will be a boost for that.
"Definitely - good to get the win," he said.
Fifty-two cyclists competed on the programme, with some heats in the 21-race event removed in favour of straight finals.
