They're like the Rugby Sevens of mountain biking - the 2013 Pig & Whistle New Zealand Singlespeed Championships is a serious sporting event wrapped in a loud, colourful party.
"Cross-country mountain-biking is often associated with men in tights," said Sullivan. "With singlespeed racing that may extend to a heavily tattooed man in a tutu ... or dressed as a Muppet."
The sixth annual championships will be in Rotorua this weekend, with race day next Saturday.
The society ran the first two New Zealand championships in 2008 and 2009 and in 2010 it hosted the Singlespeed World Championships, bringing nearly 1000 riders from 30 countries to the Whakarewarewa Forest Trail network, on the city's southern doorstep.
"We still get great feedback from people from all over the planet who were here in 2010," said Sullivan.
Meanwhile, the New Zealand championships went on a tiki tour - Queenstown in 2010, Hawkes Bay in 2011 and then Nelson, last year. Now the sport is back on the rise.
"After Nelson no one put their hand up to run this year's event, so we grabbed the chance to bring it home. There is something elegant about the simplicity of one gear. But it isn't so much a new thing as a revival."
The Singlespeed Championships will be a mix of demanding racing on some of the best trails Rotorua's Whakarewarewa Forest network has to offer.
Garth Weinberg is one singlespeeder who knows how tough it will be.
The Rotorua rider races in mainstream events as well, such as Karapoti and the Magellan Whaka 100, competing successfully with the best one-geared bikers.
Weinberg won the Singlespeed World championships in 2010 in front of his home crowd after a dramatic race-long battle with US pro mountain biker Ross Schnell.
"It was one of the most special moments of my life," said Weinberg. "The majority of the locals and heaps of the out-of-towners knew me and were cheering and screaming for me to go as hard as I could."
The Pig and Whistle is an appropriate sponsor as the event is far more social than serious.
"Singlespeeders really do race hard and then enjoy a good bit of socialising at the after-match function," said Gregg Brown from the Rotorua pub.