Guest writer Paul Duval shares his thoughtful observations about performance cornering based on electronic data gathering.
Corner speed. It is the holy grail of motorcycle road racing and track day riding alike. Knee down and railing, carving the corners like a snowboarder or giant slalom skier. It looks and feels awesome! Smooth technique pays big dividends and you can carry a lot of speed as your skills progress.
But how is it that you can be cranked way over thinking you have maxed your speed for a given corner and yet, some other dude comes by on the inside (or outside at a Tony’s Track Day!) and walks away from you before the bikes are even upright on the next straight bit?
And by the way, He’s not even leaned over as far as you are! There must be more to corner speed than meets the eye. Let’s take a closer look at the middle of a corner.
Corner Speed Perception
If we draw the arc of your path on paper it looks like a smooth outside-inside-outside line and it is easy to visualize maintaining a somewhat constant speed, decreasing and increasing in a smooth fashion, but overall steady. One could imagine their speed data trace looking similar or the same as the arc of their line through the corner. This is, in fact, how most riders perceive cornerspeed. They feel they can put a number on it.
For example, that’s a 70 mph sweeper, or a 50 mph hairpin. But something is wrong. How did that fast guy in the example above pass while you were dragging knee, elbow, boot, etc. with 57 degrees of lean angle? If he’s going faster, wouldn’t he need MORE lean, not less?
V is for Variable Corner Speed
If we look at GPS speed data from a corner, we can see the first flaw in our perception of corner speed. It is not constant. It is not even close. From the start of the arc that we drew with our bike, speed drops precipitously until it reaches a low point much slower than expected somewhere near the middle of the arc. If you perceive a 70 MPH corner, the chances are your slowest point of that turn is 50MPH. This rapidly dropping speed line doesn’t rest at the bottom for long rather it reverses course and quickly climbs out of the hole. The trace of your speed data doesn’t look like a U. Instead it looks decidedly like a V. Our minds fill in the slow spot, and we perceive a 70 MPH corner.
The Pivot Point
The bottom of the V, or the slowest point of the corner is the important spot to recognize. From here on out I will call this the pivot point. The pivot point should actually be part of your cornering plan. In other words, you need a reference point (or a few) for this spot on track. It is the spot at which your bike can change direction the most easily.
This critical moment in riding is often ignored, but it is where the real direction change happens. As you trail off the brakes, your hands get lighter on the controls until you have no weight on the bars and you allow the wheel fall INTO the turn. THIS is the spot where your grip needs to be as light as possible.
To be clear, you still need to countersteer to initiate lean. Countersteering is an important technique, but in this article, we are focused on the middle of the turn, the pivot point.
When and Where to Pivot?
Most of you are thinking, “we are talking about the apex, right”? I am avoiding the word apex on purpose. Many people refer to the apex as the point where you are closest to the inside of the pavement. This is often not the same place as the pivot point.
For example, double apex corners and increasing radius corners tend to have the pivot point in a different location than the “apex”. This concept applies to all bikes, big and small, and all lines, point and shoot, or fast and flowing. Different bikes may choose different pivot points to take advantage of the strengths and weaknesses of each platform.
- In a “fast exit” corner, the pivot point would be located earlier and you would get on the gas sooner to take advantage of that fast exit.
- In a “slow exit” corner, the pivot point is located later to take advantage off all the possible entry speed.
- In a “balanced corner” (equally fast entry/exit) you have a little wiggle room. If you need entry speed to pass a rider you can pivot a little later, if you want to out drive them on the exit then pivot a little earlier.
Similar Mid-Corner Speed
Interestingly, if you compare a fast lap and a slow one, you will often see that the mid corner speed (slowest point) of the faster rider is not a lot different from that of intermediate riders. Maybe just a few MPH, or maybe no different at all!
What you will see is that the slopes of the V in the speed data trace are steeper, usually on both sides. The faster rider is faster into and out of the corner. Understanding where your pivot point is allows you to plan the fastest way the get to it, and the fastest way to get away from it.
So here comes that fast(er) guy blowing by you on the outside into a fast corner. You already feel you are mid corner and cranked over good, but he knows that he has some yards to go before reaching the pivot point, and is taking advantage by carrying more entry speed, tipping in slower and braking later or longer.
You both reach the same minimum speed in this corner, and you feel like he’s in touch for a moment. You might even feel like your “corner speed” is the same as his, but he quickly pivots the bike and walks away on the exit because he can accelerate sooner than you. Sigh.
Time to start thinking in Vs.
About Paul Duval
Paul Duval is a fellow track day instructor, former Loudon Road Racing Series 125 GP Champion, current top runner in Supersport classes at LRRS, and professional educator. You can see Paul in action at most Tony’s Track Days events.
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