While the sight of early morning joggers is nothing unusual, there are not too many people who pound the pavements dressed in a dark blue suit and yellow runners.

"There's quite a few flats going up near us ... I get some funny looks as I run past the workers at six or seven in the morning," the 36-year-old father of two said.

"I've become a little bit well known as the guy that looks like he's running late for work when doing some of my training."

While he is on a mission, it's not to the office. Mr Tozer plans to be the first costumed City2Surf fun run entrant to cross the line this year.

He aims to raise $20,000 for the the Fragile X Association of Australia - an organisation that supports those affected by a condition that afflicts his six-year-old son Josiah.

The "virtually unknown" intellectual disability is the most common single gene cause of autism around the world, occurring in one child born in Australia every week, and in an estimated 5 per cent of all people diagnosed with autism.

Those affected tend to display developmental delays, with the condition causing behavioural and learning challenges, as well as a range of physical characteristics.

Mr Tozer said the business suit was a way to communicate the discomfort navigating everyday life can be for those who live with a seemingly invisible condition.

"A suit doesn't really [make sense in] a marathon, just like living with a disability isn't well suited to a world that doesn't adapt to meet the needs of all its citizens," he said.

Having broken the world record for completing a half marathon in the custom-made business suit last year, Mr Tozer is well placed to take out the gong in the world's largest fun run come August. However, he won't be without his rivals.

"So there's often a Superman - a guy in a Superman outfit who's out there at the front and I'm going to give the Superman a run for his money."

While Josiah doesn't quite yet understand why his father heads off in a "crazy outfit" every morning, Mr Tozer, who is optimistic he can reach his fundraising goal, trusts that he will in the years to come - proof that not all heroes wear capes.

This year's run takes place on August 13. Enter The Sun-Herald City2Surf, presented by Westpac.