TeeSquare,

I'm 5'8" 235 and have been riding about 2 months. My best is the low 14s MPH but only for 8 miles and on flat land. At the end I was trashed!. I've got to get better.

I think speed does matter some. I can plug along almost all day but I only get a good workout when I try to push the speed a bit.

Congratulations on a new best!