On turning V2.0 (cont.)

So the purpose of this blog is to share my thoughts about racing. One of the thoughts I have had over the course of my short and relatively undistinguished racing career is there is a distinction that can be made between turning and cornering. It's not that turning and cornering are mutual exclusive. They both involve changing direction, but cornering is trying to change direction while maintaining the highest possible speed on a fixed and relatively narrow course. I learned a lot of what I know about cornering on a bicycle from an unlikely source: instructional tutorials created by car-racing experts in the video game Grand Tursimo 4. Some of that knowledge transfers very easily to cyclocross.

A great deal of the collective knowledge related to the skill of cornering addresses these two questions:

Where should I be on the course?
How fast should I be going?

There are many other important questions related to cornering (equipment set-up, body positioning, etc), but I am going to ignore those for the moment. It is not that they are unimportant; they are just beyond the scope of what I am hoping to convey in this post.

Warning: I am momentarily going to touch on a possibly painful subject.........running.

On a 400m running track (shudder, shudder) the difference in length between running in lane 1 and lane 2 is about 7m per lap. Thus, there is generally an advantage to running on the shortest possible arc on the track (i.e., the inside of lane 1). Even in the most wet and slippery conditions a running “spike” provides ample traction on the rubberized surface for making the relatively gentle curve on a 400m track at the top speed.

On the running track, the inside lane is generally preferred because running the shortest distance is a competitive advantage. Races that require runners to stay in their lanes (e.g., 200m - 800m dash) have staggered starts, so everyone runs the same distance.

Cyclocross is different than track and field because the shortest path around the course is generally not the fastest path around the course. This difference happens primarily because of the faster speeds and the tighter turns of a cyclocross course relative to a running track. When turning on wheels (bicycle, motorcycle, go-cart, automobile, race car, etc) available traction is limited, and thus there is generally a negative relationship between the sharpness of a turn, and the speed at which one can safely navigate that turn. The wider the turn the more speed can be carried through the turn. The narrower the turn the less speed can be carried through.

This implies that the widest possible turn is also going to be the fastest turn. A rider can generally carry significantly higher speed through the widest possible turn, and compensate for the slightly longer distance.

This widest possible turn within any corner is known as the ideal line (or racing line) which is theoretically the fastest line around any given corner.

The ideal line is a geometric construct. It is the largest possible smooth arc that will fit inside the boundaries of the turn. In practice it means starting on the outside edge of a corner, cutting through the apex (i.e., the center of the turn), and back out to the outside edge on the far side.

In cyclocross the geometry of the ideal line is slightly different than in other disciplines of racing. There is a virtual apex that exists inside the actual apex of the corner which defines the ideal line. This virtual apex exists because the lean of a turning bicycle

From PsychoCross

combines with the vertical markers used to define the course (i.e., generally with vertical poles or other environmental objects such as a tree) and prevent the wheels of the bicyle from riding the inside edge of the corner the way automobiles can ride the inside edge.

From My Racing Thoughts

Why highlight the virtual apex? For me it’s a safety thing. To the extent that this blog is interpreted as being prescriptive or offering guidance, I don't want anyone to say "I ran into that tree because the interweb's guy told me to take an ideal line close to the apex". You have my full permission to aim a little wider and not run into that tree. Also? in my personal experience, hitting stuff has a negative impact on speed and can cause physical discomfort making the tight inside line less than ideal.

However, cyclcross courses are rarely comprised of two straight aways and a single turn. Turns flow into one another, and the ideal entry for the second turn may be on the opposite side of the course from the ideal exit for the first turn if each turn was considered separately. The ideal line then becomes almost an arithmetic average of the ideal exit of the first turn, and the ideal entry to the second turn.

From My Racing Thoughts

Navigating turns quickly means identifying an ideal line that allows the rider to flow smoothly and quickly though the turns as a series.

Having introduce the theory, what is the practical application? In automotive racing the ideal line is almost always the best line. In cyclocross racing this relationship is much weaker because the conditions of the course are very fluid from race to race, turn to turn, and and even lap to lap.

For example, I was in a race recently with a vicious turn that I remember well.

From My Racing Thoughts

It was a 180 degree hairpin to the left with a patch of very loose powdery dirt around the apex (well worn with tire tracks by my second lap), a large root running parallel to the apex about a third of the way from the center to the outside edge, and waiting on the outside of the turn was a tree who’s roots were exposed across the width of the course and whose trunk rose diagonally up from inside the course to outside the course. So at 3ft off the ground the tree was outside of the course but at 1 inch off the ground the trunk was 12 inches into the course. Riding the ideal line (outside-to-apex-to-outside) was triply dangerous because of the loose dirt at the apex, the root running diagonally away across the ideal line, and the tree inside the course.

On all of my laps I ended up cutting inside the root, and making a slower, sharper turn through the loose dirt. The entry for this turn was a wider bend to the right left me in the middle of the course or farther toward the inside of the turn making it very difficult (and slower) to try and navigate around the outside of the mid-track root. I remember this turn so well because of the Zeigarnik effect, which is to say I remember this turn so well because on my second lap I totally blew it. I mentally transposed myself to a different turn forgetting about the tree on the outside of the course. I cut inside, started to accelerate wide again, but had to slam on the brakes to avoid piling into the tree. I almost came to a complete stop, had to veer to the left, mutter a quick "I'm sorry" to the two riders who almost piled into me from behind, rebuild lost momentum and compose myself because I had to set myself up for the next turn.

This leaves us with basically three kinds of lines. There is the ideal line which is the symmetrical arc around the apex, there is an early apex turn (i.e., like the above example) where the turn starts early and is more gradual before the apex and sharper at the end, and there are late apex turns which begin with a shaper turn to leave a more gradual apex.

From My Racing Thoughts

I noted above that in auto-racing with its finely maintained asphalt the best line is generally, but not always, the ideal line. One reason why the best line is not always the ideal line is that everyone is trying to be on the ideal line. Sometimes the best line is simply the one that no one else is using at the moment. Avoiding an accident on a bad line is always faster, safer, and more courteous than causing a collision on a "better" one. This is especially true during the traffic and chaos at the start of a cyclocross race.

From Elvis is CROSS >:-| (and X-)

Likewise the choice of a best line can be strategic. Cyclocross is determined by placing, not by time so there can be a competitive advantage to using different lines when someone is closing in and trying to pass. Again, the goal is first and foremost to be safe and courteous to other riders, but there are times when taking an early or late apex can make it more challenging for an approaching rider to pass. According to the rules: "In the event two riders are vying for position, the leading rider does not have to yield his position to the challenging rider. However, a rider may not bodily interfere with the intent to impede another rider's progress. Traditional rules of racing apply: the leading rider owns the track."

There are many other reasons why a rider may “see” the ideal line for a corner and chose to ride somewhere else. For example, at Montrose Harbor last year a snow-covered course was blazen with a narrow and well worn path about 14 inches wide. Outside of the well worn track was four inches of crunchy and/or powdery snow. The only time it made sense to leave the well worn track was if someone fell down right in front of you on the track. It was too hard and too slow trying to ride through the snow. Likewise topography (i.e., up and down hills, on-camber and off-camber, etc.) also have a big impact on the best line around a corner or a series of corners. I may try to share some thoughts about riding on various topographies sometime in the future, but in the meantime you should get on your whip and practice cornering through a variety of turns on a variety of topographies on a variety of terrains. Imagine not just an inside for your turns but also imagine (or preferably mark) an outside too. Experiment with different lines and stick to the ones that feel the fastest. This whole ideal line business is simply a place to begin, a framework to apply on your first pre-ride. Let the theory be the lines (pun intended) and your own experience be the paint that gives color and depth to that experience.

All of the above tries to help a beginning rider answer the "Where" question. A subsequent post will tackle the second question: How fast should I be going?

If this post is any good it's because of constructive feedback I got on an earlier draft. Thanks for that.