Double-apex corners can be tricky
March 5, 2019
The Champ School just finished our first-ever Florida school at Palm Beach International Raceway, aka PBIR. Terrific layout with three double-apex, huge-radius corners that have a variety of lines available and require discipline and patience to get right. A special thanks to our Florida partners for making this first school so successful: Mark Thompson, John Sackett, Seth Starnes, Kat Zimpel, Chris Boy, and German Vacca. Let’s do it again!
One of the biggest “aha moments” for our students came in these long-radius corners. A double-apex corner requires an approach that puts the bike wide midcorner, where the direction change occurs in order to get the bike ready to exit. Riders are used to “slow the bike, turn, and accelerate.” That approach makes long-radius corners difficult and risky.
In the diagram below, I’ve broken the corner into three sections and added notes that include line choice, speed advantages, safety issues, braking zones, and priorities. How wide you get midcorner depends upon the length of the following straight, all things being equal like grip and obstacles.
*_An interesting note: Kyle Wyman and myself, racers of two different generations, independently came to the same conclusions regarding lines around PBIR. We were within a handful of feet of each other during our film laps…and, most notably, in the same place as track record holder Seth Starnes. Our shared priority was:_ How can I use the corner entry to get the bike ready to exit?
Please take a few minutes with the diagram; there’s a lot going on. The concepts are straightforward and logical, but the execution is not easy. This is a simple sport, but riding consistently quickly could be the most difficult thing you do in your life. Put your time in mentally to make the on-track time successful.
Section 1: Blue is faster (at the same lean angle and risk level) due to a more open radius. Orange must brake earlier, harder because Orange’s late turn-in is quite tight. Blue will brake lighter and longer; Blue will carry significantly more entry speed. In ChampSchool parlance, “Blue’s slowest point is later.”
Blue’s low, early turn-in will push the bike wide midcorner—exactly what you want. Orange’s wide, late entry will put the bike low midcorner, which is okay for a midcorner pass (see Eddie Lawson pass Neil McKenzie for the lead of the 1988 Laguna Seca 500 GP for a great example) but not good for lap records, catching or leaving other riders, or safety. Why is it less safe? Because orange must hold maximum lean angle for more time. Lean angle equals risk. Freddie Spencer says, “I want to run maximum lean angle for the shortest time possible.”
I am giving Orange the benefit of the doubt that they actually get the second apex; normally a low midcorner line puts most riders wide of the second apex (see dashed orange line). Holding or adding lean angle after the exit apex eventually gets painful. Oh, and it’s slow too.
Double-Apex Corners diagram
Section 2: Orange is faster here because Blue must slow the bike to change direction with a tighter radius. This is the only section where Orange is faster (same bike, tires, rider, risk, emotion, caffeine levels, inspiration). We always look at “time at speed” and the Orange line is faster for less time. “Slower, longer” does not win championships… And it’s not much fun.
Section 2 is the slowest part of the corner and Blue respects that by rolling shut the throttle and even braking lightly, or perhaps even braking all the way to this point, while Orange is often at partial throttle or even accelerating because Orange got into the corner so slowly.
Orange could also be following the terrible but popular advice: Accelerate through the corner. Mark Schellinger and I illustrate “Radius equals mph” on our YouTube videos for more insight on this core riding principle. We’ve got to fix the terrible advice I wrote in italics above or our sport will never grow. Read up on “The Brake Light Initiative.” Please.
Orange’s desire to start the drive to match Blue’s exit will always put him wide of the second exit… Did I mention that lean angle after the exit apex eventually gets painful?
Section 3: This is the exit, and Blue is able to initiate acceleration sooner, creating a longer straight than Orange. But much more important than who accelerates earlier is who gets to wide-open throttle earlier! Blue does.
Blue got to this wide midcorner spot with more entry speed or less lean angle than Orange. Orange is turning into the corner too late, which makes the turn-in quite sharp so Orange must slow down more or take more risk at the same speed. Orange’s technique works in simple 90-degree corners but leaves the bike in slow and leaned over at maximum lean angle for a long time in this type of corner.
Section 3 ends at the next braking zone, so if you have a double-apex corner that leads onto a long straight, the discipline to run the Blue line will pay off enormously. “Pay off” means quicker and more repeatable, safer and faster—a pretty good deal.