My ride route is just a shade under 20 miles and occassionally after anywhere from 6 - 12 miles in i will get a feeling like i am getting a little shock on the back of my thigh near the seat. It feels like it happens on the down stroke while pedalling, at first it would only happen to one leg or the other, but now it happens to both. If i pop up out of the seat it goes away, but not always. The feeling only lasts a few minutes but is annoying. I have tried searching here for an answer, no luck.