The challenge of cornering
Longitudinal cycling has a natural organization lending itself to physical modeling primarily because it can be analyzed in isolation. If a cyclist is making a steep ascent, it does not matter if they are alone or in a pack. Each must make the same effort.
When cornering, the same cannot be said. In any turn, the goal is to make the turn and emerge at the highest possible speed. The dynamics of riding in a pack are perhaps more important as the physics of making a turn. The cyclist must be able to quickly identify a path around a turn that takes into account all of the others surrounding him or herself.
This makes cornering a critical cyclist skill when riding in either recreational groups or competitive packs. We understand what is the physical force turning the cycle and the role played by leaning. In this section, we discuss how a cyclist would corner if by themselves, and some of the concepts when they are doing so in a pack.
What are cornering lines?
Cycling as well as auto racing both have the same challenge. Making an optimal turn that maximizes speed while maintaining stability, that is, completing the turn without having to dramatically alter their motion to compensate for mistakes.
The path taken around a particular curve is called a cornering line. Each has a turn-in point with some entry speed. Each follows a path to what is called the Apex which approximately divides turning-in from exiting-out.
For any given corner, there are an infinite number of possible cornering lines. There are also an infinite number of possible cornering lines which do not make the curve. In competitive scenarios, there is one optimal line which may be available to a cyclist depending on their position within the pack.
What is the Apex Point in a turn?
An Apex is defined as the highest part of something, particularly if it comes to a point. In general, it might describe someone at the apex of their career or having reach the highest point of a mountain. In turning, the Apex refers to the “peak” of the cornering or turning line located at the center of the corner.
The following is illustrated from racing cars, but is useful in understanding the nature of these various cornering lines. Here you can see the Apex is at the corner of the curve and the optimum line revolves around the Apex. It is the point where the driver transitions from going in to coming out.
Cycling cornering strategies
When auto racing, the strategy is to maximize speed around the turn which means maximizing the turn radius. Cyclists follow a different cornering line. Here you can see that turning-in too earlier or too late results in a path that may not make the turn.
There are a range of turn-in possibilities that can negotiate the turn. Turning early passes by the curve Apex and emerges towards the outside of the road. The ideal turn-in reaches the inside of the curve slightly pass the Apex and emerges the closest to the turning center.
All of this is great if you are riding by yourself or at the front of a pack. If you are in the pack, you are in a follower rather than a leader mode and your instincts as to which cornering line works in that situation will be critical to you emerging from the turn with highest possible speed.
Pack Riding: Concertina Effect
The following is taken from https://cyclingtips.com/2009/10/cornering-tips/ and provides an excellent description of some of the dynamics when taking a corner in a pack.
When riding in large groups such as criterium racing you’ll experience what’s called the concertina or accordion effect. This happens when the front riders slow down to enter a corner which compresses the pack together. The last rider in the bunch has to slow down the most. By the time the front riders are accelerating out of the corner the riders at the back are still slowing. This means the riders at the back have a lot of catching up to do and have to go faster than the riders at the front in order to catch up again. The further back you are, the more this surging effect is propagated towards the rear of the bunch.
The trick to avoiding this constant surging is to find your position at the front quarter of the bunch. You don’t want to be at the front doing all the work but you want to be close enough to the front so you can carry your speed through the corners and respond to any attacks or surges. This also enables you to read the race and see what’s going on up front
Cornering Tips from CyclingTips
The following is also from the same web page as provides some tips for how to corner in a pack.
Good cornering technique can save a LOT of energy and put you in the proper winning position in the final straight. Knowing how to corner properly can also give you what we call “free speed“. Many people have difficulty cornering so here are a few simple tips to help you along the way.
- Always look where you want to go and don’t fixate on the wheel in front of you. Never look where you do not want to go. It’s a sure way of heading in that direction.
- Anticipate the speed for the corner and brake before the corner if necessary. DO NOT brake while in the turn.
- Approach the corner wide, cut to the apex , and finish wide. The apex is straightest line through a corner and allows you to maintain the highest amount of speed. A common mistake is cutting to the apex of the turn too early. Approaching the corner wide also gives you more options when exiting the corner in case something unexpected happens.
- Quickly scope out the 2 or 3 riders ahead of you who have already entered the corner. Note if they are pedaling safely through it and judge whether you should do the same. If it happens that your inside pedal hits the pavement, don’t panic and don’t over-correct. Over compensation is how most crashes happen.
- Put all your weight onto the outside pedal if you stop pedaling. This pedal outside pedal should be facing down towards the road. Lift your weight off your saddle slightly to get that weight on the outside foot, get over the front of the bike (see photo below), and roll up behind and into the slipstream of the rider in front. It’s amazing how much speed you can keep and energy you can save by ducking right under the wind.
- If you are not pedaling through the corner and need to coast through (as in #5), once you have passed the apex of the corner begin to pedal again as soon as possible and accelerate out of the corner.
Next Topic: Cycling Stability and Balancing