There’s a robust excerpt from Racing Wisely at Trail Runner, complete with a very kind introduction.
Time trial racing means getting to the finish line in the shortest possible time. But to do that, you may need to go slow, especially at the beginning, so that you have enough energy to carry you all the way through the race. While you might be able to hold an aggressive pace for a tenth of the total race distance, you need to aim for the best average pace you can sustain for the entire race distance. This will feel easy as you begin, then gradually tougher as you continue. Your effort will continue to increase and your pace will hold steady.
This means you should always be operating within comfortable limits. You can’t hold a desperation pace for too long. As I told my daughter Lily before her first triathlon, “If you feel like you’re going to cry or throw up, slow down.” In training, especially in your time trials, you should get to know the feeling of an effort you can sustain. You’ll also get to know the signs that you’re redlining: a cold chill, a drop in your stomach, a loss of your form, a change in your breath. An evenly paced race will flirt with this edge of desperation but not tip you over it until your eyes are on the finish line banner.
There is only one reason to go out at faster than your intended pace when you are racing for time: to position yourself so you can settle in to the appropriate pace as soon as possible. Everything else is ego or ignorance, and both ego and ignorance can be controlled. Gear your training toward memorizing the pace you will hold throughout the race. Get to know it when you are fresh and when you are tired. It is your best ally: it is the best pace to get you to the finish line fast. When you know this pace inside and out, you won’t start too fast, and you won’t fade at the end. You’ll run your personal best.
Read more at Trail Runner and in Racing Wisely.