The majority of the soil in Rotorua 's mountain biking areas have the perfect balance of 40 % sand , 40 % silt and 20 % clay .
It is both easy to dig up and compacts down again perfectly .
The majority of the soil in Rotorua 's mountain biking areas have the perfect balance of 40 % sand , 40 % silt and 20 % clay , meaning it is both easy to dig up and compacts down again perfectly .