But as a Maori with a history as a civil rights activist and protester during his earlier years in New Zealand, he knew he couldn't simply roll over and be victimised by a law he believed was wrong. He'd seen too much of that in his homeland.
Grant's principles and his desire for justice would soon see him become the first-ever West Australian imprisoned for riding a bike.
"I had 30 days to pay the fine but I knew I wasn't going to because I had to take a stand against such injustice," he says.
"I refused to go before the court and I wouldn't pay the fine, but I knew it would take eight or nine months before a bench warrant would be issued for my arrest.
Instead, I went to the parole office and sought the issuance of a community work order.
"I deliberately breached the work order with the intent of having a bench warrant issued more rapidly.
When the time came, a horde of media went with me to the police headquarters in East Perth at 10 oclock at night, and I handed myself in with the warrant."
Grant spent the following two days and three nights imprisoned at the East Perth lock-up... technically for breach of a community work order, but in principle because he had ridden his bike.
"I had spent time behind bars in New Zealand as a result of protest action, but I otherwise had a totally clean record and I'd never even received a speeding ticket for driving my car or riding my motorbike," he laughs.
"Because of that past experience, my two days and three nights in a prison cell were boring rather than traumatic, the only exceptions being when I witnessed and heard police aggression.
"I watched as an intellectually disabled man was physically assaulted in the opposite cell and was angered when a drunken Aborigine was repeatedly knocked onto the concrete floor of the courtyard as he was sprayed with a firehose.
"Verbal threats were made against me, I wasn't allowed access to the few books I'd brought with me and the one phone call I was allowed was cut short when I mentioned the word 'media'. Nevertheless, I was safe because any bruising would be witnessed by the media waiting outside for my release."
The media in fact missed Grant's release as police came to his cell at 3am on the third night and told him he could go home.
During the few months between his apprehension on the streets and his time behind bars, Grant had sold his racing bike and associated cycling paraphernalia.
Although he wished to make a public stand for what he regarded as justice and democratic principles, he knew that the Western Australia cycling community would be forced to wear helmets and believed his favourite exercise pastime would be made uncomfortable, inconvenient and potentially dangerous.
"The newspaper misquoted me in saying I agreed that a bike helmet can save your life," he says. "My repeated point at the time was that there was no medical or other evidence to warrant introduction of a law which strips the fundamental civil rights of citizens in Western Australia.
"As adults, we should be responsible for ourselves and our children, and it was wrong to deny this fundamental right without any research.
"The results of the law over the past decade have proved I was correct in taking that position. The impact on public health and cyclist injuries has been disastrous.
"I haven't ridden my bike since then and four of my five closest friends also have given up. I'd estimate that more than 90% of the West Australian community is opposed to this law, and their opposition is well grounded in both medical and democratic principles.
"It's insane that I and others went to prison just for riding a bike.
"I certainly have no regrets about what happened. I'm glad I didn't pay the fine and instead stuck to my principles. The results of the law since then vindicate what I did.
"If people in other countries are faced with a government wanting to introduce compulsory bike helmet laws, I can only hope they recognise that, apart from causing untold damage to community health and cycling safety, they also face the prospect of being treated like criminals behind bars - simply because they wish to exercise."
Grant Mahy left Australia permanently in March 2006: "I now live in the free world and happily cycle without a helmet every chance I get."
West Australians are no longer imprisoned for failure to pay a fine. New legislation removes their right to choose imprisonment in their stand against laws they consider unjust, or which they believe they have not breached. Fine defaulters now have their motor vehicle driver's license suspended until the infringement is paid. If the "offender" does not have a driver's license, the court bailiff is empowered to come to their home and take goods to the value of the unpaid fine.