From their website :
In this mass participation event you can either ride or race, its up to you. The course follows through the scenic Mt Disappointment state forest over 90kms with plenty of undulating and ever changing road terrain. There is NO single track, but that's not why you're here. Its an event for the masses. Never been off road before, want something more exciting than a road race or do you just want to enjoy a fully supported ride with friends and family. The Dirty Gran Fondo is all of the above.Sounds good to me. Disappointment State Forest is an awesome place to ride and there's 90km, 65km and 35km options depending on how much dirt you think you can handle. This event is fully supported (food, drink etc. all provided) and there's even some big prizes if you fancy your chances. Oh, and they're way more organised than we are so you can expect to be treated right by a mob that are used to putting on big commercial events.
Here's a vid of MTB legend Trent Lowe talking about the course :
It's on Sunday 20th May, more details can be found on the official website.
We'll be there with bells on so say g'day as you're passing us!