Originally on v1 of patclements.com. It explains how to start in Hillsboro West End neighborhood, and cross through downtown Nashville, to create a pretty long ride.
HWEN Area to East Nashville – start at the old Wild Oats on Belmont, where it crosses over I440. Follow Belmont towards downtown, 4 way stop turn right. Go to light, turn right. Cross Wedgewood, follow bike lanes down to Musica (the naked statue). Make your way through downtown to cross the Gateway Bridge to East Nashville. Continue on down Shelby Avenue into the park. A flatter route is to turn right as you come off the bridge, and follow the river east (watch the railroad tracks) to Shelby Park. You can then do the whole park for about 26 miles, or cut it off to make the ride much shorter. Or, when you come off the bridge, circle the football stadium, and head back over the pedestrian bridge. Follow nearly the same route back to Belmont.
Multiple options – you can follow other bike lanes around East Nashville to add miles. You can circle around over to the state capitol building (nice climb). You can also cut over to the farmers market.
I have one suggestion to lengthen the Shelby Bottoms route: if you keep taking a right through the bottoms, you’ll leave via the newest exit on the back side to Moss Rose (I think that’s the name). The rule is to keep following the river by basically taking mostly right turns. It will take you to Mcgavock and Brush Hill. Eventually, Brush Hill dead ends shortly after it goes under Briley Parkway. This section adds out-and-back miles and throws in some nice hills. The roads are mostly very low traffic.
From Mick with the HBC: If you want to expand that route a bit you can cross Briley on Gallatin. I don’t recommend travelling Gallatin during peak traffic hours and definitely take up a lane where the shoulder is narrow. You only have to go on Gallatin for a mile and make a right on Emmet. Turn left where it Ts and continue to Neely Bend Rd. Make a right and go for another mile of narrow shoulders. Turn right on Center, left on Berwick trail and you are following the river again. Turn right where the road ends at School Pass road. Left on Evergreen Trail back and hook up with Neely’s Bend again. Head south all the way to En Peeler park where the road ends at the actual Neely’s Bend of the river. The Gallatin road section is a little hairy but I used to ride in traffic in San Francisco so it doesn’t bother me too much. The area along the river and down into farmland makes for a great ride.