Originally Posted by
Mobile 155
I have found they tend to fall behind at 10 MPH. At 9 they can still catch you. They can bite right through bibs or shorts and a jersey.
This has always been my uneducated estimate. I ride past an old junk car lot off of one of my trails and must go around a gate at less than 10. I have always tried to get back above 10 as quickly as possible because the deer flys seem to wait at the gate.