I rode this route on my bike earlier this summer, it was exactly 60 miles:
Layton and Farmington completed their sections of the Denver and Rio Grande Rail Trail this spring, and since the connection between the Legacy Parkway trail and the Jordan River Trail was completed last year, you can ride on a continuous trail from Bluffdale to Roy. There are two small missing sections of the Jordan River Trail in SL county, one in Sandy and another through the power plant property where the river goes under I-80 near the Fairpark, but there are easy, on street detours around both. The trail ends when it hits Bluffdale, you have to ride along Redwood Rd. for several miles through the Camp Williams area, but it eventually starts again in Utah Co. and continues to Utah Lake.
It's also cool to know that the TRAX bridge built over the Roper rail yard for the West Valley Line was built wide enough for a trail to be added in the future so that the Jordan River Trail can be connected to the Parley's trail network and the tunnel that is currently being built under 1300 E. @ Sugarhouse Park.