The grade of the Mountain Bike leg is grade 1-2 with small sections of grade 3. Refer to the MTB trail grading system on this page.
The Mountain bike event is definitely classed as Cross Country, not Enduro. So the best bikes would probably be XC or All mountain. 100mm-140mm suspension front and rear would be the most suitable. Speedsters might choose hard tails.
Some people have questioned the course profile of the MTB55km course. “Is it really all downhill for the first 35km?” The answer is absolutely YES (except for the odd 2 minute climb followed by a fun one minute descent).
Trail Walk/Run Course
The ruapehuExpress trail run is best described by Nic Leary, local top NZ Endurance athlete who has run the Old Coach road many times...
'Running the Old Coach Rd is a neat challenge - achievable for entry level trail runners and equally will test the agility and speed of experienced off-roaders. It is a 'net downhill' but be sure to wear some tough shoes and get practicing on uneven ground - the cobblestones are a cool feature of this run, but they are no highway. And, in the shade there could well be some puddles. The trail varies nicely with corridors of native bush, firm fast descents, rough cobbled sections, and farmland - energy sapping cross country running to finish! It is an interesting run throughout, the many historical features of the road and railway remind you of the busy connection it was in the early 1900s in constructing the main trunk line'.
The Old Coach Road is a stunning piece of NZ trail, but can be a little slippery and has some sections with an uneven surface so trail running shoes are probably the best choice.
Check out more on the Ohakune Old Coach Road here - http://www.ohakunecoachroad.co.nz/