thank you for your tips...
we were on Santa Ana river trail to Huntington Beach and I was averaging 16mph and one of the member averaged 24mph. i wasn't wearing tight cycling clothes and I remember the members posture was much more aerodynamic than I, lowered upper body hunched closer to the stem. I wasn't thinking about the aerodynamic but common sense hindsight...
I'll try the new tires, clothing, and posture...
thanks again for such a detailed explanation.