Route Ironman Canada Bike Course  

Where does the 'extra' 3 miles come from? The IM bike is 112 miles.

Yes. The IM route is 180km and this route is 175.5. The shortage in this route is a combination of start/end and turnarounds being inexact, and mostly from the difference between interpolation of altititude data points versus on-the-road climb/descent measurements. Any route mapped like this cannot accurately represent distances through hilly terrain better than within plus or minus one or two percent. For another map of this route, see: http://www.ironman.ca/bike.html