We’ve probably spent months, maybe even years, fine tuning the handling of our cars. We have probably spent even more time learning how to extract the most out of a car that is balanced perfectly for our driving styles. Having confidence and predictability in our vehicle’s handling is vital to extracting the most out of it in the heat of competition.
But the fact is, no matter what kind of racing we are involved in, sometimes the car just isn’t going to behave as well as we want it to.
For road racers, the most common causes of this include tire degradation, changing fuel loads, changing weather conditions, track surface changes over the course of a race, and more. The problem is perhaps even more prevalent in autocross, where the cars are typically set up to be a bit more edgy, the track surfaces and grip levels vary wildly from one event site to the next, and there is little to no testing time to make adjustments before each race. It is not a question of if the car will sometimes not handle right, but rather what we will do when that happens. The only things we can do about it are to:
- Be adequately prepared, as drivers, to make the best of the situation when the car handles differently
- Tune the setup such that the changes in handling balance across varying conditions are minimized
In this post, we are only going to tackle the former; what we can do as drivers to adapt. I cannot overstate the importance of being able to adapt our driving styles/approaches for various handling conditions. If we are only comfortable with the car when it is handling in its optimal state, we are gong to be woefully underprepared to win. It isn’t just a matter of understanding oversteer and understeer and knowing how to handle each; rather, we need to think about it more holistically, and consider how different handling conditions require us to use different inputs, resulting in different approaches to stay on the edge of grip, and thus different lines.
This may seem obvious, before we adjust our approach for an ill-handling car, we need to make certain that it is indeed the car that is reacting poorly, and not a driver induced problem. We have previously talked about how to identify and fix execution errors. Just because we get the car very sideways through a corner does not necessarily mean that the car’s balance has shifted to oversteer. It could just be an execution error through that corner.
Let’s get the basics out of the way
It is common to think of a corner as having an entry, middle, and exit phase. Unless something has gone horribly wrong or the driver has willfully induced oversteer, cars that are normally well balanced will almost always have a neutral to understeer balance in the mid-corner phase. We will discuss the technical reasons for this in depth in a future post. For now, let’s ignore the mid-corner phase, and recap how to handle understeer and oversteer during corner entry and exit.
- Entry understeer: This is solved by reducing entry speed, or by adding front grip. The most common solutions are to either brake sooner/more, or to trail brake into the corner to dynamically add weight and thus more front grip to the car in order to induce some rotation.
- Entry oversteer: Too much entry rotation is solved by reducing the amount of forward weight transfer during corner entry; i.e. by doing more of our braking in a straight line. Typically this will also result in a more geometrically circular line rather than a late-apex line through the entry phase.
- Exit understeer: We can either delay acceleration a bit until the car has completed more of its turning, reduce the intensity of the acceleration until the car has completed more of its turning, increase the amount of throttle if the car has sufficient available torque to induce power oversteer to combat the understeer, or alter our line for a later apex so that the car has less turning left to do.
- Exit oversteer: If there is oversteer on corner exit, then we have either induced too much power oversteer (RWD and AWD only), or allowed entry oversteer to carry through all the way to the exit. In the case of the former, correct using the steering wheel and/or reduce throttle as necessary, and in the case of the latter, add throttle in order to add more weight/grip to the rear to stabilize it.
Knowing how to handle each of these scenarios is one thing, but making the most out of an ill-handling situation requires us to analyze the behavior of the car through the entire corner, and adjust our approach accordingly.
Looking at it more holistically; through the entire corner
There are 4 ill-handling combinations for us to consider…
- Entry understeer – Exit understeer: When a car that is normally well balanced exhibits understeer on entry and exit, it is usually a sign of worn out front tires, or could also be caused by too much front roll stiffness for the amount of grip provided by the surface. Our job in this scenario is to find ways to dynamically add grip to the front of the car, and/or lessen the amount of turning we are asking the front tires to do. We can accomplish this by trail braking into the corner to add weight/grip on the front tires and remove weight/grip from the rear tires, in order to rotate the car more on corner entry. By doing this, not only are we dynamically adding front grip, we are also making the front tires less responsible for turning the car with the rotation from the rear helping to turn the car as well. During corner exit, there is nothing we can do to add front grip, as the very act of accelerating takes away front grip. So the only thing we can do is to choose a late apex line such that there is less lateral grip needed from the front tires on corner exit. When done correctly, this approach will allow us to carry more speed into the corner, while maintaining a higher than usual slip angle at the rear to help turn the car, on a late apex line that allows us to accelerate better out of the corner.
- Entry understeer – Exit oversteer: This is a condition that will only manifest for RWD or AWD cars, and is a classic symptom of worn out tires, or a low grip surface, where neither end of the car can provide the needed grip. The lack of front grip makes the car understeer when we try to turn in, and the lack of rear grip makes the car oversteer when we try to accelerate out. Our objective is to dynamically increase front grip and/or reduce the demands on the front tires on entry, and to dynamically increase rear grip and/or reduce the amount of lateral grip we are demanding from the rear tires on exit. There are 2 different approaches (and lines) we can utilize to combat this. The first approach involves trail braking on entry to add front grip, and utilizing a later apex to straighten out the exit and lessen the lateral grip required from the rear tires. The second approach involves the use of a double apex, where we carry a ton of speed into the corner on a flatter early apex arc, thereby reducing the demand on the front tires on entry, trail in and pitch the car to get it rotated mid corner, and utilize a second (late) apex to straighten out the exit so we can accelerate out of the corner without placing too much demand for rear lateral grip. This approach generally only works on tighter 180 degree turns, but is very effective in that situation.
- Entry oversteer – Exit understeer: This affliction is perhaps most common on FWD cars that have worn out tires, or mid/rear engine cars with insufficient front roll stiffness for the grip level of the surface. The problem is caused by too much forward weight transfer (or too much rear lateral weight transfer) which results in insufficient rear grip during corner entry, followed by too much rear weight transfer leading to insufficient front grip during corner exit. Our objective in this scenario is to minimize the amount of weight transfer during corner entry in order to maintain rear grip, and lessen the amount of turning remaining on corner exit in order to minimize the impact of understeer. We accomplish this by doing more of our braking in a straight line before entry and using a more circular (rather than elliptical) line towards the apex, which will put the car into a steady state cornering balance sooner. If oversteer still occurs during entry, it can be handled with steering corrections or by adding a small amount of throttle. On exit, we would utilize a later apex so that more of the direction change is already done, and the exit understeer is tolerable while accelerating out of the corner. Alternatively, if our RWD car has enough torque to induce power oversteer, we can use that to overcome the exit understeer.
- Entry oversteer – Exit oversteer: Drifter’s paradise perhaps, but alas, not particularly fast. Unless something is gravely wrong, or there is some really extreme torque vectoring going on, this condition will never occur in a FWD car. A RWD car that is normally well balanced exhibits these symptoms when the rear tires have worn out, or the car has too much rear roll stiffness for the grip level of the surface. Our goal in this scenario is to try to keep as much weight as possible on the rear of the car at all times in order to maximize rear grip. The approach involves braking in a straight line before corner entry to avoid unloading the inside rear tire any more than necessary, and applying light throttle on corner entry to maintain a steady speed on a circular arc towards the apex. We would make use of a later apex in order to straighten out the exit so that we can accelerate out of the corner without demanding high levels of lateral grip from the rear tires at the same time. Alternatively, in certain corners we may be able to use the double apex approach described above. The intention would be to apex early without much turning, use the car’s oversteer tendency to get it rotated quickly mid corner, and take a second late apex to power out.
Each of the scenarios described here assume that your car is usually well balanced. None of these approaches are going to be faster than the optimal line through a corner, but when the car is handling poorly, our objective is to make the best of it and lose as little time as possible, instead of losing large chunks of time from unnecessary slides or being out of position. If your car always handles in one of these ways, certainly you can still use these techniques to make the most of it, but there are likely significant setup improvements that you can make to your car that would make driving it at the limit much easier, and much more rewarding.