Strategies in track riding/road racing: Finding the limits of traction...safely - Page 3 - ZX6R Forum
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post #31 of 72 Old 11-22-2015, 03:10 PM
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Originally Posted by PainfullySlo View Post
Thanks Petrol, I thought it was just me.

Cwik, I really do appreciate your input but I am not sure how else I can explain it other than what has already been said.

This is my last ditch attempt to try to clarify this. Again, when speaking of the apex in a turn, it is the riders apex that we are discussing. Perhaps I could have been clearer somehow in establishing this during my initial writing but everyone else seemed to grasp the concept.



The riders apex, the point at which he/she is turning the most, is independent of the turns apex, be that the natural apex (centermost point in the radius of the turn) or the forced apex (the classic late apex line shown in the diagram).

I have edited my original post to add as much possible description to the term "apex" to avoid any potential confusion for future readers.
Look up rider's apex and driver's apex. Doesn't exist. You are making up the term. I provided Wikipedia's definition of an apex and that is precisely what every credible source defines as an apex; the part of the turn where the driver comes closest to the inside of the turn. It would appear that you are trying to describe the apex (rider's apex) as the slowest part of the turn for a given line, but the term apex, in any practiced definition, does not describe that point. Refer to my post #18 in this thread.
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post #32 of 72 Old 11-22-2015, 06:37 PM
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Originally Posted by Petrolsexual View Post
It is your lucky day! Youtube recommended me this video, and wouldn't ya know it, it is as perfect a demonstration of what I've been talking about as I could hope for. He brakes for a corner, tips it in, trail brakes, opens up the throttle just before the apex but isn't accelerating just settling the bike, then AT OR AFTER THE APEX he begins accelerating out of the corner. A pro, doing it exactly how it should be done.

https://www.youtube.com/watch?v=vuVXHij79xU
I tend to disagree. I hear plenty of times where the rider is on the throttle before the apex. And not just holding speed, but there is a rising frequency in the sound. Keeping in mind that accelerating is defined as any change in speed over time. And that should be the case. A rider/driver should be gradually shifting from turning to accelerating such that he is using 100% of the friction circle at all times. I wish I had software to be able to overlay the frequency of the audio in real time. That would get more objective viewpoint.

That said, I also can't tell the context in which the video was taken. Was this during the race? Time Trials? Practice? This could affect how they ride.
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post #33 of 72 Old 11-22-2015, 06:54 PM
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Originally Posted by Petrolsexual View Post
Also, because you are struggling with taking in and understanding the whole picture I'm going to take 1 specific thing you said and explain why it is wrong. "A late apex line is really just an artificially created increasing radius turn.". That is literally the opposite of what you are doing. Lets break it down into points through a corner:

1. Just beginning to tip into the corner- Speed=x1 ; Lean angle=y1
2. A couple feet later- x2<x1 ; y2>y1 (Your speed has decreased and lean angle increased)
3. A few more feet later- x3<x2 ; y3>y2
4. At the apex- x4<x3 ; y4>y3
Please provide the basis of this. All you've done is stated what you've been saying in a more mathematical form. Its arbitrary without an actual analysis.

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Originally Posted by Petrolsexual View Post
QUIZ TIME!
If you decrease your speed in a turn what happens? A: The radius of your turn decreases.
What happens if you increase your lean angle in a turn? A: The radius of your turn decreases.

SO... that means your are carving a a decreasing radius arc down to the apex which is the opposite of an increasing radius. After the apex, once you are accelerating, now your arc is increasing. And if you are at all still skeptical, just watch that video until it clicks.
Take a look at the attached photo. I took a suggested late apex line that I found on google and plotted points on it and used a spline feature to plot the entire line. Its got its limitations, but for the purpose of this analysis, it shows my point clearly. Using an evaluation tool, I had it show the curvature. The series of lines perpendicular to the curve represent its curvature at that point, where the longer lines represent a greater amount of curvature (tighter radius) and the shorter lines represent a larger radius. Its very clear that the tightest radius occurs early in the turn and gradually straightens out from there. To make the best use of the friction circle, the rider/driver would have to add throttle as that radius increases. It would be done so gradually to try and maintain 100% use of the friction circle.
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post #34 of 72 Old 11-23-2015, 10:53 AM Thread Starter
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I give up. I hope that others find this less confusing than you apparently do.
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post #35 of 72 Old 11-23-2015, 08:25 PM
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Great write up Slo,

This is what I've been trying to work for the last few trackdays. I still find myself having to think about staying loose on the bars and that doesn't help with my communication with the front end.

"Apex" I feel like it has taken over this very informative post. The apex is relative to the line you are taking. Maybe CK has enough money to ride on the track alone, he doesn't have lap traffic or anyone trying to pass him. He has the luxury to take the same line, hit the same brake marker every time, and never have to alter his apex.
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post #36 of 72 Old 11-24-2015, 07:59 AM
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The apex or clipping point is the innermost point of the line taken through a curve. The apex is often, but not always, the geometric center of the turn.

Within the context of motorcycling, the apex refers to the point where the motorcycle is closest to the inside of the corner and not necessarily the center of the corner. Because motorcycles need to lean through corners and the risk associated with the lean, it is desirable to limit the time leaning over as much as possible; as such it is a popular technique to delay the apex until some point in the second half of the turn.

https://en.wikipedia.org/wiki/Racing_line

According to the Wikipedia, the apex can move. lolwut.

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post #37 of 72 Old 11-24-2015, 11:53 AM
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Thanks for the info PS, PLEASE keep up the good work and continue these write-ups!

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post #38 of 72 Old 11-24-2015, 12:49 PM
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Donkey punch lol.
Great write up. You always see a wannabe Rossi heating his bum up.!..
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post #39 of 72 Old 11-24-2015, 01:25 PM
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Thank you, this is very informative!
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post #40 of 72 Old 11-24-2015, 01:27 PM
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Quote:
Originally Posted by commiehunter View Post
The apex or clipping point is the innermost point of the line taken through a curve. The apex is often, but not always, the geometric center of the turn.

Within the context of motorcycling, the apex refers to the point where the motorcycle is closest to the inside of the corner and not necessarily the center of the corner. Because motorcycles need to lean through corners and the risk associated with the lean, it is desirable to limit the time leaning over as much as possible; as such it is a popular technique to delay the apex until some point in the second half of the turn.

https://en.wikipedia.org/wiki/Racing_line

According to the Wikipedia, the apex can move. lolwut.
Wikipedia for you.
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post #41 of 72 Old 11-24-2015, 01:46 PM
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Originally Posted by PainfullySlo View Post
I give up. I hope that others find this less confusing than you apparently do.
This has nothing to do with him finding it confusing, is has to do with cornering though - Have you tried the "fastest lap calculator"? And in that case, what do you think of it? Thinking of buying it, i just dont know if its really worth it.
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post #42 of 72 Old 11-24-2015, 02:01 PM
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Let me just interject with something.

There are more than one line through any turn. Because there are multiple lines through any given turn there are also multiple apexes to any given turn.

True... the defined "apex" of a turn on paper would be the mid point of the arc of the turn. But that arc can change. So in my mind the apex is always defined by the rider at the time while negotiating that turn.

When setting up track days we place a cone at the preferred apex of every turn to give people a clear visual. I can tell you that almost never is that cone placed directly on the mid point of the main arc of that turn (assumed you're looking at it from above)... it's placed at the apex of the turn.
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post #43 of 72 Old 11-24-2015, 02:40 PM
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Wikipedia for you.
No, that's the point. The apex is based on the rider's line. It does move based on what line you choose. It is not a fixed, unwavering, technical point. It is the point where your line is closes to the inside of the turn.

I'm just backing up PainfullySlo, little though he needs it. As these diagrams show very clearly, 'Late Apex' means you push that chosen point later in the turn. This all seemed very very basic and easy to understand to me until someone decided it could not be so.


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post #44 of 72 Old 11-24-2015, 04:16 PM Thread Starter
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Originally Posted by Enrosabil View Post
This has nothing to do with him finding it confusing, is has to do with cornering though - Have you tried the "fastest lap calculator"? And in that case, what do you think of it? Thinking of buying it, i just dont know if its really worth it.
Not sure exactly what that is but I assume it is something similar to the 'best theoretical lap' option that is a part of my QStarz laptimer software.

It has its uses, but also needs to be taken with a grain of salt.

For instance, my software will pick apart my laps by the entire track broken down into little segments then add up the fastest segment times to give you a 'theoretical best lap'. Meaning if you did everything right, that is your optimal lap time. It is good for a goal but it is inherently flawed as your fastest times in a particular section are highly dependent upon your entry and exit lines...which are affected by your earlier section trajectories. Still, it makes for some interesting discussion.

Here is the thing about lines, and this goes WELL beyond the intended scope of this writing. For the vast majority of turns, there is no magical one right line. (the one line to hold them and on the asphalt, bind them!)

One of my favorite questions to get (sarcasm) when instructing is for riders to ask me to show them my line with the assumption that I am fast, so my line must be the fastest line, right? Now, I understand why people ask me this and so I just chuckle and offer the following explanation:

Lines are determined by the rider skill, handling characteristics, and speed of the motorcycle. As all 3 of those things can vary quite a bit you will find that what works for someone else may not work for you. Hell, I even have different lines depending on which bike I am riding. For example: my line through turn 9 at my local track is completely different on a 70hp SV650 than it is on my 127hp ZX6R.

So, to me, those 'fastest lap calculators' make for some interesting fun and can certainly offer some insight, but overall there is no way for something like that to be 100% accurate. Hope this helps!
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post #45 of 72 Old 11-24-2015, 07:35 PM
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Originally Posted by PainfullySlo View Post
I give up. I hope that others find this less confusing than you apparently do.
I don't find it confusing at all. My original argument was that the apex is not the slowest part of the turn (which is what you said). If you make this assumption, your posts make sense, but take that assumption out for a moment and try and understand the physics. Look at the photo I posted in my last post. I think you can agree that the tighter the radius of the line a rider takes, the slower he has to go. If a rider takes a late apex, the line will require a tighter radius at the beginning. Which means THAT is the slowest point in the corner. If you want,I can prove it mathematically. Just ask.
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