Taking a longboard downhill is a lot of fun and it can be a great way to experience a rush of adrenaline. The trick is to control your speed, so you don't run into unnecessary dangers. There are several different techniques to control your speed and slow down your longboard.
The most important thing to remember is that you must wear proper safety gear. This includes a sturdy helmet, pads, and gloves. Some riders even opt for a full-face helmet. You'll also want to get a hefty pair of knee pads.
It's not uncommon to see people sliding when they go fast, which is the key to controlling speed. You can also use shoe breaking at lower speeds, but it's not recommended after you've picked up a certain level of speed.
This is because the board's center of gravity is lower. This reduces the need to look down as much and gives you more reference points for your feet. The board can also flex and this can make it unstable at high speeds. It's best to try on smaller hills and flat surfaces while you get the hang of certain techniques. Youtube has plenty of tutorials on this. You may also want to consider looking for lessons in your area from your local shop.
Things to consider:
Make sure you do your research on the proper wheels and deck style before you start. For wheels you'll have two choices: you can either pick something grippy which will help you taking sharp turns and carving; or you can pick a stone grounded wheel with rounded edges. These wheels are designed to help you achieve sliding. Keep in mind the wider the wheel, the grippier it will be. The bigger the wheel, the easier it will be to ride over irregularities in the road.
Also, having the right deck will make a big difference in your speed. If you're going for stability, the best choice is a double drop through deck which has a deep concave built into it to lock your feet in place. These are known as freestyle decks.
If you're going for top speed, there are specific deck styles designed for racing called downhill decks. These are top mounted decks cut similar to a skateboard but a little longer with a point in the front.
Downhill longboarding Is not for the faint of heart. Make sure you wear a helmet and other protective gear when riding.