Terrain, weather, age are all variables that must be taken into consideration.

For us:
Terrain: rolling to mountainous. Very little flat terrain.
Weather: Very windy springtime; warm (100+ degrees) from May into October). Dry, very little rain. Ideal weather from late Oct. to April (70s, sunny).
Today's tandem toot, May 15: winds +/- 20mph, temps 93 degrees, cloudless/sunny. Yes, some hillwork.
Our average speed was 11.3 mph
Best average speed ever was a hilly ride of 43 miles at 21.5 mph average; but that was 20 years ago!
Back then we averaged 14 to 18 mph.

Our

Our ages: 78 for pilot and 76 for stoker.
Our f-a-s-t days are behind us!
Our motto:Growin' old is not for sissies!
Pedal on!
Rudy and Kay/zonatandem