This is an excerpt from Complete Triathlon Guide by USA Triathlon.
Cornering on the Bike
You also need to think about actually driving the bike and some of the more dynamic movements you have to make while racing around a course. One of the areas where athletes lose speed is in corners. These athletes lack the knowledge and the confidence to navigate a corner while slowing only slightly and letting their momentum carry them through safely and back up to racing speeds.
There are a few methods of steering a bicycle at race speed. The most common are the lean and the steer. Many variables affect which method you use including road conditions, turn location, entrance speed, and number of other athletes near you as you approach the corner. I will touch on each and how you might practice them.
Remember to shift your bike while keeping a higher cadence in order to prevent dropping your chain. Also, be one or two steps ahead on the bike course, and shift your bike into the appropriate gear before you head into a corner. You don't want to stand out of a corner either spinning without pressure on the pedals or mashing the gears.
The lean is the version most cyclists know and use in higher-speed conditions. This involves leaning the bicycle into the corner as needed, based on the radius of the curve and the speed at which you enter the corner. You will be leaning, but at a slightly lesser angle than the bicycle. For many athletes in mass-start triathlons or other multisport events, the safest method is to pedal normally until you are approximately 70 to 100 yards or meters from the apex of the corner (the center point of the radius, usually). At this point, you will decide if you need to coast or brake before entering the corner. If you need to apply the brakes, do so gradually, and remember your front brake provides most of the power to slow the bicycle. More advanced athletes will remain on the aero extensions (if a nondrafting event), while beginner athletes might sit up and drive from the base bar.
Just as you enter the corner, pedal half a revolution so your outside foot is at the 6 o'clock position, and apply pressure with it toward the ground. This “pushes” the tires down and helps settle the bike. Keep your body equally balanced between the front and back tires. Lean your bike and then your body in sync as needed, and continue to push on that outside foot. Now let the bike roll. (When you brake hard in the corner, you tend to throw the mass of your body forward, and this unsettles the bike and can cause the wheels to come off your chosen line.) As soon as you are clear of the corner, start to straighten the bike, and you can pedal away safely, hopefully without losing too much momentum.
Once you have mastered the lean and feel comfortable doing it, you need to work on the next progression: the steer. If you have practiced the lean, you will notice a few things. First, you don't actually turn the handlebars much (or thus the front wheel), and second, you are really moving through the corner on a small contact patch of the tire on the outside edge of the tread. This tends to be the preferred method for higher speeds or dry conditions.
When the situation calls for it, you will need to steer the bicycle through the corner. This varies slightly from the method used for the lean. You will set up much the same, but the major difference is that the speed will be lower (think 180-degree turnaround or rain-soaked corner). So, you will start to brake earlier and most definitely will be driving from the base bar (or hoods for a road bike). The outside pedal is still weighted. Now, as you approach the apex of the corner, you will turn the front wheel as needed based on approach speed and radius of the corner. Here is where it gets a little tricky! You will still lean through the corner, but mainly your body is leaning into the apex and the bike is staying more upright. This is not an extreme body lean—think more of “leading” the bicycle a bit. The goal is to keep the bike more upright and thus keep a larger contact patch of the tire on the road. Once you have rounded the corner, you straighten the body and bring the front wheel back in line and
A good skill to practice at low speed in the grass with a few friends is bumping each other from the sides or brushing their rear wheels with your front wheel. This will help you become accustomed to contact between riders so you react calmly to it when it happens in a race.
One of the most frequent questions asked by new athletes is “When do I shift?” This is a tough question to answer. There isn't really a right or wrong time, just the optimal time. A modern racing bicycle has between 18 and 30 available gears and the mechanisms to shift through those gears at the flip of a lever or the push of a button.
The terrain and a rider's output (watts) will dictate when the shift should happen. It's best not to overthink the simple act of shifting, but you should be aware of a few things not to do. First, avoid the cross chain; this is the gearing when the chain is on the biggest (outside) chain ring in the front and the biggest (inside) cog in the rear. A modern bicycle will operate just fine in this gear combination, but it adds undue stress to the drivetrain, and especially the chain itself, increasing wear. The simplest solution is to shift down to the inner chain ring in the front and then shift down two or three cogs in the rear and find a suitable gear ratio with a much better chain line.
The next scenario that is best to avoid is a drastic shift in multiple gears while pedaling under heavy load. Usually when you see an athlete drop a chain off of the front chain ring, it is when he has tried to make a quick multiple-gear change under load; the derailleur tension cannot compensate for the rapid change in chain position, and the chain can drop off the chain ring, falling into the bottom bracket area or toward the outside of the big chain ring. This comes down to the issue of course knowledge, as this situation usually arises when you are caught off guard by a steep climb or sharp curve. It is not always convenient to arrive early or the day before an event, so you have to use your best judgment when navigating the course if the terrain is new to you. The safer option is to be in too easy a gear and keep your cadence a few rpm above your self-selected range, as it is always easier to drop to a harder gear than it is to try to force the chain up the cassette to a very easy gear.
The question also comes up regarding the correct rpm, or cadence, to maintain. Cadence is a very individual metric. Some athletes “mash” the big gears, and others are “spinners” who ride at a very high cadence. In many instances, these athletes get around the course quickly and are still able to run well off the bike. Experience has shown that the sweet spot in cadence likely falls from the high 70s to the low 100s, with most folks falling very near 90 rpm. For more info on the optimal cadence, see chapter 12.
While racing in triathlon, I mentally check my cadence every 5 miles [8 km] on the bike. It is important to keep a higher cadence while on the bike to lessen muscular fatigue before heading out onto the run course. If you slow your cadence down too much, it can greatly affect your run performance.
Most of this chapter is spent covering topics to make you go faster on the bicycle. But the truth is, sometimes proper braking will yield overall faster bike splits. It's important for an athlete to understand when to brake (such as before a tight turn) and then accelerate out of the turn. It is also important for the athlete to know how to brake downhill, feather the front brake, and apply consistent pressure on the back brake with your weight shifted back. Remember, momentum on a bicycle is hard to get but easy to keep, so if a rider is smart with her application of brakes at strategic times, she will lose less overall speed and maybe avoid a worst-case scenario—a crash.
Earlier in the chapter, potentially hazardous aid stations were mentioned to emphasize the importance of proper bike handling. Here is a possible scenario. Picture this: You are 30 miles (48 km) into your Iron-distance bike leg, and you slow to retrieve a bottle of sports drink from the aid station. Just then the athlete in front of you slams on his brakes, and you run straight into him, sending you careening. Your day could be over. Don't let this happen to you! When approaching aid stations, come off of your aero extensions and ride on the base bar, covering your brakes with a single finger on the lever. Look for a volunteer down the line a bit, and make your way toward her while feathering the brakes. Note: Most aid stations are set up on the right side of the road, and you will be reaching with that hand for the bottle (or other nutrition), thus you are covering the front brake. Continue to look for other athletes, and drag that front brake a bit to scrub speed; grab the bottle on the fly, and ease yourself back into the course properly. If stowing the bottle in a rear mount behind the seat carrier, take caution in doing so, and try to get clear of the aid station and back up to speed. Most important, pay attention and be prepared to take evasive action if needed.
There are two important things to remember when participating in a rotating pace line. First, as you drop to the back after a pull at the front, stay close to the side of the riders behind you. This allows them to continue drafting off you as they move forward. And, second, do not dramatically accelerate your speed when you move to the front. This will cause gaps in the group and slow the overall pace.