Reading The Track
Published: August 20, 2015
A crucial skill of an advanced driver is the ability to read the track they are driving. As instructors eventually have to instruct on tracks they have not driven, track reading is also a crucial ability of a successful instructor.
"Reading the track" means figuring out what inputs to apply to the car when - when to brake and how hard, when to turn in and how much, where to position the car at every point on the track, when to get on throttle. A different way of looking at the this process is to say that the driver is figuring out the line that they are going to drive.
There are four types of corners we can identify. I arranged them in the order that drivers typically consider and master them:
- Exit speed corners lead on to straights. These corners typically call for conservative entries and late apexes, especially when learning the track.
- Setup corners, which are used to prepare for the following corner. Setup corners are sometimes called "throwaway corners".
- Entry speed corners follow straights and do not lead to other straights, hence are not exit speed corners. In these corners the idea is to brake as late as possible, even if it compromises the line through the corner or exit speed. These corners benefit from trailbraking and, often, aggressive entries.
- Corners that can be eliminated. Some of these corners are so open compared to dimensions and grip level of the vehicle that they can be taken under full throttle with varying lines. Other corners are parts of corner complexes and the entire complex can be taken with a line which makes a corner in the middle disappear.
Well-known examples of each type of corners are:
- Exit speed: Summit Point turns 1 and 10, Watkins Glen turns 1 and 11, VIR Oak Tree turn, Pocono turns from infield into oval, Palmer turn 6, NJMP Lightning turn 5.
- Setup: Summit Point turns 7 and 8, Watkins Glen turns 2 and 3, VIR turns 4, 5, 7, 8, 11 and 16, Palmer turn 13, NJMP Thundebolt turn 9.
- Entry speed: Summit Point turn 5, Watkins Glen bus stop entry, VIR turn 13, Pocono North oval into infield transition, Palmer turns 5 and 8, Thompson turn 5, NJMP Lightning Lightbulb.
- Eliminatable: Shenandoah turn 6, VIR turn 2, Palmer turns 7 and 11.
While most corners belong rather clearly to one of these types, there are exceptions. For example, Summit Point turn 1 is generally treated as an exit speed corner, but it really is both an exit speed and an entry speed corner. NJMP Lightning turn 3 is roughly equal parts setup and entry speed corner. VIR turn 11 is primarily a setup corner but it is partially an entry speed corner. Lime Rock turn 1 is roughly equal parts entry speed and setup corner.
Identifying corner types involves, for the most part, vision, experience and critical thinking. A driver must look at the corner as a whole to be able to figure out what type of corner it is. Novice and intermediate drivers generally do not have sufficiently developed vision to pull this off, hence reading tracks tends to be a skill learned fairly deep into one's track experience. The next step is comparing the corner to a mental database of all the other corners the driver has driven - what known corner does this corner resemble the most? Finally, the driver must understand the importance of exit speed and going faster everywhere, and that higher speed is better than slower speed. Some drivers have "driving smooth" as their principal goal, and this essay assumes the driver cares first and foremost about overall speed, as would be measured by lap time. Aggression also comes into play here.
We have looked at corners horizontally; it is now time to go vertical. Famous elevation changes include Lime Rock uphill and downhill turns, NJMP Lightning turns 1 and 5, VIR climbing esses and rollercoaster entry, VIR hog pen, Summit Point turns 3, 4, and 5, Watkins Glen esses and turn 6, Palmer turns 1, 5, 8, 9 and 10.
A vehicle that is climbing a hill generally has more grip than the same vehicle driving on a flat surface, and a vehicle that is descending a hill has less grip. Of similar importance is what happens when said vehicle crests the hill (quite common) or goes through a dip (rather rare). A cresting car unloads the front suspension and then the rear suspension; when the unloading happens, the respective end of the car loses grip. A dipping car loads suspension and hence experiences a momentary increase in grip as the front and the rear traverse the dip.
How do we put this knowledge to use? A turn that transitions into a hill, such as NJMP turn 1, requires less braking than would otherwise be needed and permits higher entry speed. VIR rollercoaster entry is very much the same, with cars braking very late considering the length of the preceding straight. Lime Rock uphill turn is so extreme that experienced drivers in Miatas turn half as much as one would on flat ground at the turn in point, performing the rest of rotation on the ascent.
When a car is cresting a hill, we expect the front to unload which tends to produce understeer, and then the rear to unload which tends to produce oversteer. In corners where the apex is around the crest of the hill, such as NJMP turns 1 and 5, the adjustment is to run a later apex in the turn so that the car has less lateral grip demands when the rear unloads. Such adjustment permits early power application - in both of the NJMP corners, the ticket is to start applying throttle before the respective crests.
On the downhill side, the grip is generally reduced but whether the car understeers or oversteers depends on car setup and its power level. Traction sensing takes over.
More subtle elevation changes are often overlooked by less experienced drivers but they provide a significant benefit to drivers that are able to exploit them. Palmer turn 5 is an uphill, permitting late braking. Palmer turn 9 is also uphill, permitting more aggressive throttle application. Palmer turn 3 is rather subtly uphill - many drivers lift for it when lifting is not necessary.
Downhills scare people because they reduce available grip. An observant driver however can note how steep the downhill is, and come in with an expectation of how much grip would be reduced. This builds confidence, which ultimately unlocks speed. Lime Rock downhill turn, Summit Point turn 5 and Palmer turns 8 and 10 are good examples of downhill corners that can be taken with confidence.
Camber changes the grip of the car side to side rather than front to rear like elevation does. While exact car behavior depends on the specific car, many vehicles exhibit understeer when they are on an off camber part of the track approaching a corner. The principal remedy is to trailbrake more aggressively; an earlier turn in may help as well. Banked (in camber) corner entries tend to favor earlier turn ins also but that is because the car should be carrying much more speed compared to flat ground.
Shenandoah has significant camber and camber changes in many corners, including 3, 5, 6, 7, 11, 13, 17 and 20. Watkins Glen turns 1, 5, 7, 9 and 10 are significantly cambered one way or the other. At VIR the camber comes into play in Hog Pen.
Observing camber and adjusting for it permits precise car positioning in cambered corners, and as a consequence enables the driver to increase their speed through such corners.
Increasing And Decreasing Radius Corners
Driving corners of changing radius well is a matter of good vision and, for decreasing radius corners, trailbraking and car setup. Vision is required to identify that a corner is in fact opening up or tightening. With that knowledge, increasing radius corners call for earlier power appication while decreasing radius corners call for trailbraking and curving the approach into the corner.
Decreasing radius corners used to make me uncomfortable but once I mastered trailbraking - and especially how hard I trailbrake, from very light braking to keep some weight on the nose to aggressive trailbraking to break the rear tires loose and thus rotate the car - decreasing radius corners everywhere became lots of fun.
Changing track width effectively makes a corner have increasing or decreasing radius. In the Northeast the track width differences are incredibly stark at Pocono - the oval being easily double the width of the infield pavement, most corners from the infield onto the oval open and can be taken under power while corners from oval onto infield tighten and call for trailbraking and curving the line on approach.
Other tracks have more subtle track width changes that are nonetheless significant and can be taken advantage of. VIR turn 3 has a wider exit after the repaving and thus opens, and turn 10 gained width at the exit with the result being earlier throttle application. Shenandoah turn 17 tightens while turn 18 opens.
Many drivers use the curbs but coast over them. This generally is not a fast way around a race track.
First step with curb usage is figuring out which curbs can be driven over without damage to the car. Taller curbs like the one in NJMP Thunderbolt turn 1 are generally best avoided. Most curbs are technically usable by most cars. Whether a particular curb should be used depends - the heuristic I use is if I can maintain full throttle over the curb, I will use the curb. If a curb is used, it is generally worthwhile to use all of it. Watkins Glen turns 1 and bus stop, VIR turns 5b and 8a, NJMP Thunderbolt turn 3 chicane exit are great examples of curbs that make a big difference if cut.
It is generally a good idea to adjust the line for the peculiarities of the car you are in. Everything covered above are guidelines that are starting points for experimentation. Not all cars can achieve all feats described in this essay. In HPDE context, the newer street cars which are physically larger, heavier and use street tires often have trouble fitting elegantly into the corners and transitions. Adjustments would have to be made.
Another aspect of guidelines is that they are not always the ticket. As Emilio Cervantes says, clocks don't lie. If you are lapping the track quicker, whatever you are doing is working - keep doing it. Above 8/10ths debates of which line is faster or "better" without data to back up a particular viewpoint become less and less meaningful.
I personally used data, specifically predictive lap time/real-time delta, segment times and theoretical best times to drive most of my development as an intermediate and early advanced driver. Over time I developed traction sensing and vision skills to the point where I used data for validation but not much for guidance. However, data remains essential for validation at 9/10ths and up.