I agree! I have had dogs and they often do have very easy tells, but that is when you know them. I have seen our dog (my avatar) get what we call the "wolf look" yet not betray any major body language. Her entire look would change, The eyes would get stone cold, the ears get a bit flatter, and the front legs would get stiff. Tails may still be wagging, but she definitely did not like that person or dog and was in a defensive mode. She was not aggressive and if approached would always put an object between her and the stranger until she decided it was time to meet.

I have out sprinted a dog in a straight line on a country, but that was because they were dumb chasers. The odds of the rider successing greatly diminishs in traffic, cross streets, or with other cyclists on a path. (Just do not be the slowest ). Our Australian Shepherd (a herder through and through) could instantly read the terrain and object of interest and adjust his direction so no matter what track he was on was the the shortest and most direct intercept. I saw him do it in the dog park as the dogs raced around, but otherwise he was never off leash even though he would reliably drop to a down position at a whistle. That was a real save when he took interest in a raccoon that proved to be rabid.

I love dogs, but as in the quote above, YOU SHOULD NEVER TRUST A STRANGE DOG. I do carry the spray, just in case.