"It was just unbelievable and we just had to finish the day early," said series organiser Allan Willacy.
"We are very disappointed we couldn't get through the whole programme, but rider safety comes first."
Cole, on his Red Devil Racing Kawasaki ZX10R, had already won both Formula One races and looked comfortable doing it.
However, engine difficulties at both Hampton Downs and Manfeild meant seventh was the best he could hope for in the Tri Series, as Christchurch's Dennis Charlett (Underground Brown Suzuki GSX-R1000) rode sensibly to take home the title.
Unlike his competitors who were thinking of the series, Cole just wanted two race wins and was so dominant he eased up on the throttle at their conclusions.
"At first I thought I could hear another bike catching me, but it was just the echo from my own bike's noise bouncing back off the buildings," he laughed.
"I backed off because I wanted to bring it home safe and sound in the end.
"I don't know what makes me go so well on the street circuit. I just treat it like any other race.
"I have learned a lot over the years from following guys like Andrew Stroud, Craig Shirriffs and Dan Stauffer.
"I guess I was doing the teaching today."
Wellington's Sloan Frost (BMW S1000RR) was second and third in Wanganui to finish three points behind Charlett.
Fellow Suzuki stars in New Plymouth's Hayden Fitzgerald and Auckland's Ray Clee, along with Christchurch's Ryan Hampton (Honda) round out the top five.
In other results, Palmerston North's Glen Williams was a double title winner as the Suzuki ace claiming the silverware in both the Formula Three and Post Classics pre-'89 classes.
The BEARS (non-Japanese bikes) class was won by Katikati's Rhys Holmes (BMW 1000RR), with dual-class campaigner Frost finishing runner-up.
Wanganui's Richard Dibben (Honda) won the super moto class by two points from Tauranga's Duncan Hart (Yamaha), with defending champion Toby Summers (Yamaha) in third.