Bikers are a community. They’re brethren. Bikers look out for each other on the road.
Who one wave to differs from biker to biker. Most bikers only wave to the people who’re riding the same kind of motorcycle as them. Some are fussy/particular enough to only wave at someone riding the same model and make. And then there are the good samaritans. The happy-go-lucky. The good guys who wave at everybody, irrespective of their bike (or even a trike!)
The reason riders wave is like a show of solidarity. It’s mutual respect and acknowledgment of the fact that how dangerous riding can be. And also an acknowledgment of the freedom that comes from riding on two wheels.
Different riders ride different machines. And nearly all the time, they pick up the style of waving particularly to their machine. These are the three most popular styles of biker waves.
The Harley Wave
You’ll generally find Harley riders giving this to other Harley riders only. The way to do it is to raise one’s left hand off the handlebar nonchalantly. Then, you take the hand to thigh level and sign an inverted-V with your index finger and your middle finger.
The symbolism behind this is that Harleys are meant to be ridden on two wheels only. They’re not the machines for riding recklessly. And it’s a sign of remembrance for the rider to ride safely.
The Goldwing Wave
This may be called the “Goldwing” wave, but it’s no more exclusive to the bike. It has sort of becoming the wave for a lot of guys who ride Japanese motorcycles, that is, Hondas, Suzukis, Kawasakis, and Yamahas. It did originate with Honda Gulwing riders, though.
The way to do it is that you move your left past your fairing. This is done while the hand is at shoulder height, with the elbow bent. Then, you proceed to literally wave your hand back and forth.
The Sportbike Wave
This is something you’ll only see guys on sportbikes doing. Ironically, it’s a bit like the Harley Wave. This is, although, not done just “nonchalantly” but almost as if you just don’t care.
The left hand is dropped to knee level, and a quick flip wave is given. Unlike the Harley Wave, you don’t do it with just the fingers, but the entire palm of your hand.