Most heavy vehicles on Waiheke Island have undergone new tests since a new brake machine was installed at the island's only testing site, New Zealand Transport Agency says.
VTNZ broke the inspection rules by operating a less effective brake test on the island for 18 months.
A total of 1038 heavy vehicles were tested this way for their Certificates of Fitness.
Since August, when a new roller brake machine was finally put in, 811 of these vehicles had a new COF test.
NZTA said it had been in touch with the other 227 owners to say VTNZ Waiheke has agreed to re-test their brakes for free on the new machine.
"The NZTA is encouraging affected vehicle owners to ... arrange for their vehicles to be re-tested."
RNZ has asked the agency for the figures of how many vehicles that passed the less effective brake test and went on to fail on the new machine.
Earlier, VTNZ told RNZ 18 customers had their vehicles retested and all were up to standard.
It denied breaking the test rules, even though NZTA believed otherwise.