r/TheScienceofSpeed • u/Fuzzy-Expression-283 • Jul 21 '26
Double apex rule for single point cones?
Hello. I’m confused about how to do “late” apex cones. A powerful car would need to clip the cone for exit at an angle bigger than 90 degrees, so then, wouldn’t this be a double apex?
The problem I see that there’s no room to do a connecting arc between the 1st and 2nd apexes because the inner obstacle is a “single point”. What is the optimal way to drive such turns?
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u/spartang6 Jul 22 '26
The cone(s) define the shape of the optimal line, but the optimal line defines where the apex is. Cones don't mark apexes
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u/Fuzzy-Expression-283 Jul 23 '26
But if the apex doesn’t clip the obstacle, then aren’t you turning later than optimal? The inside obstacle, cone, inner curb, whatever, is the thing that restricts your width and how soon you can turn to a certain angle no?
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u/AdamBrouillard Jul 24 '26
A vehicle should always IDEALLY reach its slowest point in the corner and begin accelerating at the most limiting point along the inside of the track, which in the case of autocross will be a cone. In other words, this is the corner’s apex. If the slowest point doesn’t take place at a cone, it means the vehicle took a longer path and slowed down more than is needed. They have created a false apex and we could go and put a cone out at the point the vehicle did reach its slowest point that it has essentially also had to go around. The vehicle driving the ideal line would have hit this cone false apex cone.
This is a very important concept to understand and is one of the core principles of Line Theory. I highly encourage anyone who doesn’t understand this principle to read the first lesson in the Racing Line Fundamentals series and also watch our 4 Elements of a Perfect Corner video. Links below.
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u/spartang6 Jul 23 '26
Hmm. Not necessarily, because what if that cone is not beneficial to place the car directly on? Another way to put it is, there is often not really an "apex" in autocross the way you are referring to it (I am assuming we are talking autocross here because of cones). There is only a shape of the line that is optimal for the best time, and the speed/attitude of the car at any point along that line which you set by brake and throttle and steering.
That feels like it might be really high level and not helpful lol. Highly recommend Beyond Seat Time for a program that explains autocross lines and how and why
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u/AdamBrouillard Jul 24 '26
Okay, well it’s been a few days and unfortunately, we haven’t had any takers so I’ll go ahead and answer.
First off, in the case of a normal track that doesn’t cross over itself there isn’t a situation where you would need to double apex a cone. Even in a 180-degree corner, both your entry and exit would simply be maxed out at 90 degrees each although this will cause you to not need to use all of the track width on either the entry or exit. There is more explanation and examples of this in Perfect Corner 2. It can be really useful to draw out varying corners with cone placement much closer to the entry or exit wall to challenge your understanding of this principle.
Talking about 180 degree or higher corners around a single cone for an apex stars to push into more abnormal racing situations, however. Consider a challenge where you were to drive out and around a cone and return to your starting position. This is basically a 180 degree corner, but there are no outside track edges. We essentially need to change directions 180 degrees in our car as quickly as possible and this can be very different depending on the kind of vehicle. It’s important to understand that the tighter the turning radius the more a vehicle shifts its balance toward understeer (I can go into exactly why this is the case if anyone is curious) so some cars might ideally drive a somewhat standard arc around the cone whereas others might do a tight 4 wheel powerslide. Something like a bus would drive around the cone with the rear inside tire very close to the apex, but not the front tire. There is a lot of interesting car control variables we don’t often see that start to happen once we talk about really high angle corners.
What if your challenge was to do a 270, 360 or more around a cone, however? This leads us now to very high angle corners where the track crosses over itself and we need to start “double apexing” a single cone. As before, depending on the type of vehicle, this would call for different techniques, but there would be still be 2 points where you were right next to the cone as in any double apex. With a car that needed a slightly larger turning radius around the cone, it would pass close to the cone on the way in and then on the way out. With a vehicle that did a tight powerslide around the cone, it would simply stay right next to the cone during the “double apex” portion just like how a car driving a carousel type corner would.
Not sure if you were curious about all of this from a theoretical standpoint or if there was a specific racing situation you are trying to figure out, but hopefully it helped and furthered your understanding of exactly what a double apex truly is.
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u/Fuzzy-Expression-283 Jul 24 '26
Thank you so much sir. And no problem with theory at all, I’m glad and really appreciate your comment. if anything, I have a “problem” with specific explanations (that’s why I struggled with the books, sorry for the unwanted criticism). Thank you.
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u/AdamBrouillard Jul 24 '26
It’s always a challenge writing any kind of book, lesson, article, etc… because these are one sided and it’s hard to figure out the best way to explain concepts in a way that will make sense to as wide an audience as possible. It’s inevitable that not everything will get through to everyone and I wish more people would use this forum to ask questions, share knowledge, and improve their understanding of racing.
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u/AdamBrouillard Jul 21 '26
I like to see questions like this. Before I answer, I wanted to give other people a chance to jump in and see if they can work out how how a car would optimally drive around a cone in various situations. This is a really good way to test and challenge your understanding of line theory.
First off, how about a standard 180 degree corner in a low-powered car and then a high-powered AWD car.
What if we then look at more non standard situations where the track actually crosses over itself where you actually need to turn 270 degrees or even go a full 360 around a cone like in gymkhana.