Jeffries, initially unaware of the ongoing police investigation into the burgled professor, said the finding - occurring in both tyres which also had missing valve caps - led him to call Brady, the owner, and ask: "Has someone been tampering with your car?"
Jeffries, who has regularly serviced Brady's vehicle for a number of years and declared it well-maintained, said the defects were unusual and seemed to be intentional sabotage.
"I believe someone's deliberately let the tyres down," he said.
Jeffries, speaking on Thursday morning, said he understood police would soon arrive at his premises to gather evidence.
A police spokesperson said their wider investigation into the burglaries was "ongoing and we are looking at all lines of inquiry" and they were aware of recent developments.
"We can confirm that concerns have been raised in regard to the victim's vehicle and we are investigating these," the spokesperson said.
Motoring expect Clive Matthew-Wilson, editor of the Dog & Lemon Guide, said the sabotage "absolutely" posed a risk to human life.
"It makes the car extremely unstable in its handling, and the brakes become a lot more unreliable," he said.
He said tyre-tampering was "not uncommon," but typically was only seen in clashes between feuding neighbours or lovers.
Matthew-Wilson said this specific case seemed to be connected with Brady's work on China.
"This is a deliberate attempt at harassment, almost certainly. I doubt very much that it's a coincidence. It's designed to make her feel insecure and reluctant to bring up this issue again," he said.
Brady said the incident, particular in light of recent events, worried her given the car was regularly used by her family.
"Of course I'm concerned about the safety of myself, my lovely husband and our three teenage children," she said.
"I'm also really concerned about the escalation of activities aimed at intimidating me and stopping my academic research. It appears whoever is doing this believes there are no consequences for doing it in New Zealand."
She was unwilling to comment on the lengthy and still unfinished Police investigation, but told the New York Times in September the lack of comment or public action from government to date was "starting to look like procrastination".
A Herald investigation into the Brady break-ins can also reveal the case is being handled by the Police's National Security Investigation Team, a secretive unit that is understood specialises in national security cases - including terrorism - and works closely with the New Zealand Security and Intelligence Service.
The only time the NSIT have previously come to public attention was in February of this year when they made submissions successfully opposing the parole of Imran Patel.
Patel was jailed in June 2016 after being found guilty of distributing and possessing extremist material supportive of Islamic State.
The submission from the NSIT revealed Patel had his passport cancelled in 2013 after attempting to leave the country and fight in Syria, and authorities - citing national security concerns - later declined his application for new travel documents.
The ongoing investigation - and the publication last September of Brady's Magic Weapons paper outlining a nexus of political donations and board appointments for prominent New Zealanders - had raised the temperature of local debate on the issue of China.
Commentary in local Chinese-language media has been an especially heated, with a recent op-ed by Morgan Xiao - published simultaneously by SkyKiwi, the Mandarin Pages and the New Zealand Chinese Daily News - describing Brady and other New Zealand-Chinese democracy activists as "anti-Chinese sons of bitches" who should "get out of New Zealand".
Freeman Yu, whose New Zealand Values Alliance has started a petition urging the government to follow Australia's lead and curb China's local influence, was also called out by Xiao.
Yu said the language used in local debate had recently hardened, with "extreme expressions used in the Cultural Revolution".
"The language used in their articles expressed intense hatred for different voices and the freedom of speech," he said.
Since May the Herald has been seeking to interview Prime Minister Jacinda Ardern about the governments' China policy in light of Brady's research and legislative action in Australia.
The Prime Ministers' Office has regularly put off the request, citing a desire to first finalise Ardern's first visit to the Asian superpower.
That visit, initially flagged to occur by November, is understood to have experienced numerous delays and is still awaiting signoff from Beijing.
