From Whanganui to Pipiriki it is almost 100 km on a side road. The route is beautiful and has a steep incline from time to time, which provides great vantage points (Teararoa Trail) ATTENTION: There are information boards that are NOT up-to-date. If you walk this route (like me...), take enough water with you. Because a restaurant was closed (closed on Mondays) and there was no other campsite (although the information board indicates a campsite). Pipiriki is only the next place where you can definitely get something (also has a campsite, which is NOT listed on the information board at Whanganui).
Here is a video of the route: