Cyclists then kick in for the 25km dash to Inglewood, followed by the final 17km back to New Plymouth.
It was Haden's first time entering the event.
"Got away with Gordon McCauley, the old legend, he's still got some go on the flat," said Haden.
"We made a good gap on the field until he had some bad luck with a front puncture as we hit the main road near Stratford.
"I put the hammer down and 'soloed' it back to New Plymouth from there for a comfortable win."
Conditions were overcast but dry for most of the race, with Haden finishing just after 1pm.
The win helped ease the disappointment of the 4th annual Gravel & Tar, which was going to be Haden's biggest race of the year as one of New Zealand's only UCI-graded events, which attracts a strong international field.
It consists of 90km on tar seal and 40km on gravel, starting at the Feilding Town Square and finishing at Memorial Park in Palmerston North.
"I had made a move half way through on a gravel sector and escaped off the front of a small leading group," said Haden.
"Unfortunately suffered a puncture and had a long wait before receiving a wheel from service vehicle.
"I put my head down and managed to ride back to the front group, where we continued riding hard to what was looking like a 5-up sprint for the win, until I punctured again less then 5km to the finish."
Haden got another wheel and then race off to hang onto fifth place, "which was a great result for me".
"But left me with a few restless nights of thinking "what if I didn't puncture?".