But it was only a few months ago that Mrs Heenan, an experienced pedaller and triathlete, found out that her neighbour was harbouring a bicycle made for two and teamed up with her for new challenges.
The pair are keen to take advantage of the first opportunity for the public to ride over the bridge with approval from the Transport Agency, which was overwhelmed by an illegal crossing by about 2000 cyclists and walkers in 2009 pushing for their own pathway.
They will line up from the Pt Erin Swimming Pool for a 15km excursion over the bridge, then up and down the Northern Busway from about 7am, an hour after the start of a 110km race of members of a heavier duty "lycra" cycling brigade.
Then from 8am, it will be the turn of children to take part in shorter 8km or 2km rides with their families along sections of the busway from Smales Farm, where there will also be entertainment and cycling education activities until midday.
An entry price of $10 will entitle them to a certificate and tee-shirt each, and has been reduced since the event was first mooted.
But the registration fee for the 110km race remains at $110, and the 15km bridge and busway jaunt will cost participants $15 each.
Other participants in the cycling events will include Auckland Mayor Len Brown, triathletes Hamish Carter and Debbie Tanner, and a goodly turnout from the cast of television soap opera Shortland Street.
The agency has given approval for up to 9000 cyclists to cross the bridge, but organiser Callum McNair believes many potential participants have been pre-occupied with other events such as the Rugby World Cup and the election.
Even so, he hopes his events can survive as regular fixtures on Auckland's community calendar, and that momentum will grow once people become more familiar with them.
"Being a year one event, there are a lot of people unsure of what we are about," he told the Weekend Herald.
"Are we a hard-arsed cycling organisation, are we a community cycling group, and really we've got to put the rubber on the road and show people we are actually both."
"Then I think people will get it, but seeing is believing with these things."
A number of cyclists will wear slogans of the Getacross Campaign, which wants a shared pathway across the bridge, a goal which he and the tandem riders support as a way of fulfilling Mr Brown's aspiration to turn Auckland into "the world's most liveable city."
"Certainly cycling plays a part in that," Mr McNair said.
But he paid tribute to the Transport Agency for approving the events, and to the drivers of 160 Metrolink and North Star buses who will line up their vehicles along the motorway north of the bridge from 1am tomorrow to form a 2.3km protective wall for the cyclists.
That will keep motor traffic away from the cyclists, who will reach the busway from the bridge's eastern or seaward clip-on lanes.
