The first thing you need to be sure about is your bike. Is it up to rapid hill descents? If the spokes are loose, the brakes barely working, the chain slack and the handle bars out of line then the answer is no. Some bikes are better at hill descents than others are and badly maintained bikes are not suitable at all. If your bike is in a poor state of repair then you shouldn’t be out on it at all and you should definitely avoid hills. A well-maintained bike will have no trouble descending hills however steep.
There’s no doubt that there are dangers involved in descending a hill at speed, and a well maintained bike will soon pick up speed. When I bought my Allez I was out on a run and I reached 45MPH descending a hill, this can be frightening if you don’t know how to cope with it. The first danger is obviously the brakes. You cannot stop at 45mph by applying your brakes. Your braking distance has increased and if the road is wet, you can add to this distance to take into account wet rims. If a rabbit decides to jump onto the road as you are descending you will have to be ready to negotiate your way around it because stopping suddenly is an option you do not have.
Another danger is from holes or gravel. You need to be concentrating a 100% on your descent. This is no time for daydreaming, total focus is required. Watch the road ahead for any potholes or gravel, both hazards that could send you skidding off your bike if you cannot negotiate them. Obviously, you always have the problem of cars to contend with, this is second nature to most experienced cyclists and finally there’s the road condition. If the road is wet, your problems intensify.
Anticipation is the key to safe hill descending and being aware of the limitations of your bike. Because your braking distance has increased, don’t follow too close behind cars. If a car in front of you slams the anchors on, you may end up sliding across its roof if you are too close. Remember the brakes on a car are better than yours. If a car driver gets nervous descending a tight bend and brakes, you need to be well back so you can brake.
Keep your speed down on the bends. You don’t know what’s waiting for you around them. There could be anything from a broken down car, a pedestrian or a big hole that some telecom company has dug. Don’t go round a bend at top speed unless you are in a competition and you know there is nothing there. If you don’t know what’s round there ease the brakes on. You can’t afford to gamble on a bike.
Ease your brakes on when negotiating a tight bend. As well as giving you some control should there be a nasty surprise waiting for you, easing your brakes on will also give you more traction. Because you are travelling downhill, most of your weight will be on the front brakes so this will be working more efficiently. You can combat somewhat this by moving your riding position.
Common sense, total concentration and anticipation are the keys to descending hills safely. There’s one ride I go on for a few hours where during the ride there are a number of hills following each other like waves. There’s no bends just straight road so I’m quite comfortable descending one hill at speed so I can hit the other hill with momentum. Each hill will provide its own challenges. Until you are comfortable, descending hill just take it easy and exercise caution.