My tactics (depending in dog/s and circumstances):
1- THE COMMANDO DEFENSE- a sharp, loud command of, "NO!"or "Stay!". Volume and timing are critical here. OR For the dog that is running towards me with a combination of barking and a wagging tail and has the look of a "family dog" but is stimulated to chase then I start with "Good dog!" "Atta boy!" "Come on!" if that fails I immediately switch to the first option.
2- THE WATER BOTTLE DEFENSE - a well timed spray to the face of a dog will at least slow them down or stop them. Several sprays may be necessary as you keep riding away.
3- THE SPRINT DEFENSE- this used to be my first and only option but it really doesn't solve the problem unless you're really fit and can get the bike up to 30 mph+ under virtually any circumstance. It's tough uphill, on tour with luggage, on dirt roads and the worse part is it actually stimulates many dogs into a highly aggressive mode and, if you fail, you've got a supercharged dog to deal with and no other options but a fight. It also sucks for dogs that you have to pass every day because now they think of you as a prey and will go for you aggressively every time you pass. Works good for day rides or tours where you've got an obvious advantage speed wise and will never see the dog again.
4- SPRAY REPELLENTS- I've used "Halt!" Spray, which is effective on all but the most aggressive dogs but in truth the water bottle works just as well most of the time. But this saves your water bottle for drinking. Pepper spray's downsides are cost, you can use it up on one or two dogs, it can clog and you need pretty good aim. THE COST EFFECTIVE ALTERNATIVE- make your own. Go to the local dollar store and buy some bottles of hot pepper sauce, a jar of cayenne, white vinegar and lemon juice (delicious, right?). Take an empty liquid dishsoap container (the smaller 9 oz. container works best) and mix your ingredients. Carry it in a jersey pocket or in an easily accessible place in a front bag- keep a stash fermenting at home and refill when necessary.
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