I'm actually quite surprised and a bit disappointed just how many people are willing to stick the boot in to an animal.
I suppose the above will give the K9 SAS another chance to regurgitate the devil dog scenario and the right to defend yourself, which is obviously true, but lifting your feet to an animal is not the answer.
You are the only poster to mention "sticking the boot into an animal". The OP would not have been exercising the right to defend himself unless he was being attacked, which seems to have been unprovoked and sudden enough that he couldn't get his bike in between himself and his attacker in time. Was the dog injured? Apparently not. Was the OP injured? Manifestly, yes, and fortunate not to have further injuries.
Most of the other posts have been fairly balanced and certainly haven't sought to demonise dogs. I have had run ins with dogs over the years, but most of my experiences have been positive. As a last resort I would certainly use whatever objects I had to hand to defend myself if I had to.
To their owners they may be their loyal, affectionate fur baby companions, they're "just playing" even when they bark and chase you, "they don't mean it" when they snarl and bare their teeth at you, but for people on the receiving end of the activities of a poorly trained dog, it's no joke. Many people have a fear of dogs, maybe from a childhood experience of being bitten, or a more recent experience. The old saying, "every dog is allowed one bite" is all very well, until you're the one it bites. In the grand scheme of things, actual dog bites are rare, but the fear of it happening affects many people, and one occurrence spreads like ripples on a pond to affect others who hear about it.
Going on about "K9 SAS" and "regurgitating the devil dog scenario" is not helpful. It might work for tabloid newspapers who like to demonise
social groups, but I hope we're better than that here. Either your dog is properly trained and under control, or it's not, and the penalties for that should be more stringently applied.
I suppose that there will now be a torrent of posts from dog owners stating how well controlled their dogs are. My dog never does this, that, or the other etc, and no doubt they are right. Nobody is going to post about what a rotten, uncaring dog owner they are, and what an unruly slavering monster their particular mutt is.
It just seems rather self indulgent to be a dog owner and enjoy the benefits of pet ownership, then expect the rest of the population to have to put up with the downsides if you don't put in the effort to train it and keep it under control.