- 271
- United States
- The__Ghost__Z
In my previous topic I discussed the notion of drifting efficiently as a form of racing technique. I also set the precedent for what qualifies as drifting, and its short-term goals should be, in these discussions. Lastly, I expressed (though did not fully explain) a form of drifting that achieves the maximum speed through a corner possible while still producing a full drift. This technique, a form of the brake drift, uses an over sensitive braking system to initiate a drift with the minimal body roll or speed loss necessary. Some further explanation of this technique will be revealed at the end of this.
In this thread, I am going to focus on precision and tuning. It must be understood, as a reader, you are capable of doing "merely" a drift. If you are not, you won't gain anything from this. You must be capable of having a greater slip angle in rear than in front of your tires, and maintaining acceleration and counter-steering throughout a corner. This is much like a novice throwing a 240SX around a parking lot. However, there are more precise and refined techniques that can optimize a drift in relation to driving technique. While much of drifting is indeed technique, it can still be reduced to mathematics. Some basic principles must be understood:
1. Weight Transfer VS Load Transfer: Load transfer refers to the "weight" of the car placed upon each individual wheel at a time, and is a natural effect of wheels supporting a form of weight. Weight transfer however, is very similar, but is affected by the location of the center of mass as the body responds to load transfer. Thus, a car with lose suspension will suffer the same load transfer as a car with tight suspension, but there will be greater weight transfer as the car's body rolls more, and thus its center of mass moves more.
In drifting, using weight transfer to initiate your drifts will affect overall cornering speed as greater amounts of body roll puts greater pressure and load on the outside tires. The more weight transfer you have, the more camber is necessary to optimize, though the more load transfer you have, more camber may not necessarily increase cornering speed, to a certain amount. Because all cars have body roll and weight transfer (suspensionless vehicles, such as karts, do not have innate body roll, but the movement of the driver will move the center of mass significantly, so it effectively is a form of weight transfer) Then there is always an optimal level of camber to use. In my experience, the optimal amount of camber is equivalent to the angle of body roll achieved at max cornering G forces. Since stickier tires will produce greater G forces, and thus load transfer, and thus body roll, greater camber is required. Greater camber than that will only produce more tire contact with the road on slightly banked corners.
2. Polar Moment of Inertia, or Second Moment of Ineteria: This can be simply explained as the response for all parts in a car to react to change in direction. Mathematically, it is the measurement of the distribution of mass from the outside of the center of mass of an object. In a car, how much a part resists change in motion (think of it as how a frame flexes) is directly related to the car's overall polar moment of inertia. A heavier car, in addition to having greater load transfer, will also have individual parts heavier, and heavier parts farther from the center of mass. However, theoretically, if a heavier car has a greater percent of mass closer to the center of mass, such as a heavy weight in the center of a piece of paper, it will have a better (low) polar moment of inertia than a series of interconnected wood blocks the size of a piece of paper that weighs slightly less. This analogy is a bit of a schlep, but it should express to you why Mid Engined cars, which have their heaviest components (Engine, Transmission, drivetrain, electronics, passenger, interior, speakers, etc.) all centered in the middle of the car. Understanding how this works lets you adjust your car accordingly.
Calculus and Vectors can be used to figure out Polar Moment of Inertia, and basic algebra can determine body roll and load transfer, but I will not do that here today because drifting is about technique and you can go to the tuning forum if you need more precise measurements. I'd rather not divulge all of my tuning secrets publicly, either. The two principles I just stated should draw a few conclusions from you, if you read this right so far. First off, adding weight to the center of a car, if the added weight has a greater density than the components of the car, should improve its turn-in speed, it will change direction faster. However, because of additional weight overall, it will have greater load transfer and body roll, and a lower straight-line speed due to a lower power-to-weight ratio. What this means is in tuning certain cars with poor polar moment of inertia, you can improve it by adding weight (or adjusting where your weight is added) by a small amount and achieve greater response in cornering. If a car's transitions are poor, because of the cornering response, this is something you can do. It can improve already heavy drift car's response, but ONLY if those drift cars are sufficiently large enough that it centralizes the mass. A prime example is a 1970 Dodge Challenger. It has 50/50 weight distribution, so adding weight into the middle will not affect its handling, except that it will lower the already wide and relatively lower density car's polar moment of inertia, allowing it to have less resistance in the change of direction it has. Chassis reinforcement on GT5, as well, should reduce the polar moment of inertia slightly, as there is less "give" for the frame of a car to resist the change of motion by strengthening important parts of the car.
While the location of the Center of Mass on an XY plane does affect static (no movement) grip on the tires, it is its "Z axis" location, or how high it is in relation to the tires' contact patch, we are concerned with. The higher the center of mass is, the more pronounced weight and load transfer and thus body roll will be. This means to improve the weight transfer of a lightweight car, instead of adding weight, you can lift the car higher in the air. Cornering speed however, is slightly reduced as because the more weight transfer on the tires from static position, the less overall net grip they will have when cornering at the limit and beyond. This can also be used to help drift cars that get too much grip. This decrease in overall grip at the limit will produce some under-steer as the outside tires have a greater portion of the car's weight on them. This means for heavily over-steering cars, lifting them up into the air on their suspension will help calm them down.
This is unfortunately a very long post to fully explain a few principles, but to sum it up: Weight and Load transfer are different, and controlling them affects your drift significantly. Suspension tuning for camber is related to those, and heavier cars have greater load transfer. Taller cars have greater weight transfer. Taller and heavier cars have greater load and weight transfer. Minimizing this transfer gives you greater net grip, and having a worse weight transfer lowers your net grip. Polar Moment of Inertia affects how quickly a car responds to a change in direction. A lower polar moment of inertia, where more mass is centered around the center of mass, will change direction quickly. You can use the ballast to adjust this, to affect cars that have too slow or too quick changes of direction.
Now then, as promised, a further elaboration of the optimal drift technique I've been working on:
The Brake-Lock drift (as I am calling it for now) involves causing the front wheels to lock, rather than the rear, in a straight line and then uses their excessive slip to begin a four wheel drift that reduces a car's speed faster than a simple lift-off or throw in technique, but reduces it to a less extent compared to an e-brake technique. This causes a moment of four-wheel drift before the accelerator is used. The reason this drift is the fastest is as follows:
1. Because the only weight transfer, initially, is forward and outside, maximum grip from the tires overall is maintained once the drift begins, as the car drifts very flat and maintains higher net grip, and is able to suffer greater G forces around a corner.
2. The wheel that receives the greatest weight is the front-outside wheel. When the drift starts, it must be maintained at a shallow angle or else it will devolve into a slower form of drifting, but an angle at or below the maximum slip angle for the tires will also cause pronounced snap understeer. When controlled, this produces an extremely quick termination of the drift, allowing you to exit corners very very fast, at higher speeds than normal cornering. This is the main reason that the drift is close to grip speeds, when using the slow-in-fast-out technique, because it enters at a higher speed and exits at a higher speed, with minimized loss of in-corner speed. Because of the heavy use of brakes right before the corner, and then the sudden throw-in immediately afterwards, the front-outside wheel's additional weight (and thus grip) pulls the car to the outside. Thus, by adjusting just how much pressure is on that wheel (which is done by modulating how smooth the brake shock and turn-in is), you can easily drift at shallow angles and use its grip to pull your car away from too much oversteer, which would result in a slower drift. On cars with higher levels of weight transfer, this can result in *negative* weight on the other 3 wheels. This means that the wheels are receiving lift forces exceeding gravitational forces on them, and the only thing keeping them on the ground is unsprung weight. In order to properly use this technique, a car must have minimal load transfer, which means having a low polar moment of inertia, as well as a low center of mass AND low G cornering forces, which is why it is optimal for lightweight, smaller cars on low grip tires, but becomes less useful on higher grip tires or heavier vehicles.
Right after the drift begins, the entire car pitches up onto the front outside wheel at the beginning of the turn, which regains traction first as the car begins to oversteer after the initial hard-brake. The reason an E-brake is not optimal, in addition to what I've stated before, is that it does not create this pronounced weight transfer onto this crucial front-outside wheel that will help control your angle, and thus prevent traditional speed loss associated with an e-brake drift. In this, the speed loss once a corner is entered is caused through the turning forces of the car, much like a lift-off style drift, but with the initial shock of the front wheels locking. Another advantage of this technique is that it allows a drifter to use and control higher brake pressure numbers than before.
In order, the car's actions are:
1. Gentle Braking in a straight line
2. Sudden, hard braking in a straight line, front wheels lose traction
3. Gentle trail braking into the corner with sudden turn-in
4. Rear wheels lose traction, 4 wheel drift begins
5. Power is applied to the rear wheels. Front outside wheel regains traction and maintains a shallow angle despite power to the wheels. Weight begins to flatten out as the front inside wheel regains traction fractions of a second later. 4 wheel drift is over, 2 wheel drift begins.
6. Countersteering and normal drift exit procedures, accelerating out of the turn as usual until all four wheels regain traction, first with the front-outside wheel which snaps the car into alignment automatically and allows no wasted time to straighten the car out as it accelerates at max throttle out of the turn early.
However, there are significant limitations to this drift. Because it uses minimal weight transfer to use most optimally, it can rarely be combined with throw-around techniques such as the "Scandinavian flick". It requires a car to be as low to the ground as possible and flat, which means on hills, inclines, and banked corners it becomes a less effective drift and difficulties in maintaining its load transfer become more obvious. For a track such as Tsukuba or Indy, where inclines are minimal, it is very fast. If utilized properly however, it can be used to greater effect downhill than uphill due to the increased weight on the sensitive braking front wheels.
In this thread, I am going to focus on precision and tuning. It must be understood, as a reader, you are capable of doing "merely" a drift. If you are not, you won't gain anything from this. You must be capable of having a greater slip angle in rear than in front of your tires, and maintaining acceleration and counter-steering throughout a corner. This is much like a novice throwing a 240SX around a parking lot. However, there are more precise and refined techniques that can optimize a drift in relation to driving technique. While much of drifting is indeed technique, it can still be reduced to mathematics. Some basic principles must be understood:
1. Weight Transfer VS Load Transfer: Load transfer refers to the "weight" of the car placed upon each individual wheel at a time, and is a natural effect of wheels supporting a form of weight. Weight transfer however, is very similar, but is affected by the location of the center of mass as the body responds to load transfer. Thus, a car with lose suspension will suffer the same load transfer as a car with tight suspension, but there will be greater weight transfer as the car's body rolls more, and thus its center of mass moves more.
In drifting, using weight transfer to initiate your drifts will affect overall cornering speed as greater amounts of body roll puts greater pressure and load on the outside tires. The more weight transfer you have, the more camber is necessary to optimize, though the more load transfer you have, more camber may not necessarily increase cornering speed, to a certain amount. Because all cars have body roll and weight transfer (suspensionless vehicles, such as karts, do not have innate body roll, but the movement of the driver will move the center of mass significantly, so it effectively is a form of weight transfer) Then there is always an optimal level of camber to use. In my experience, the optimal amount of camber is equivalent to the angle of body roll achieved at max cornering G forces. Since stickier tires will produce greater G forces, and thus load transfer, and thus body roll, greater camber is required. Greater camber than that will only produce more tire contact with the road on slightly banked corners.
2. Polar Moment of Inertia, or Second Moment of Ineteria: This can be simply explained as the response for all parts in a car to react to change in direction. Mathematically, it is the measurement of the distribution of mass from the outside of the center of mass of an object. In a car, how much a part resists change in motion (think of it as how a frame flexes) is directly related to the car's overall polar moment of inertia. A heavier car, in addition to having greater load transfer, will also have individual parts heavier, and heavier parts farther from the center of mass. However, theoretically, if a heavier car has a greater percent of mass closer to the center of mass, such as a heavy weight in the center of a piece of paper, it will have a better (low) polar moment of inertia than a series of interconnected wood blocks the size of a piece of paper that weighs slightly less. This analogy is a bit of a schlep, but it should express to you why Mid Engined cars, which have their heaviest components (Engine, Transmission, drivetrain, electronics, passenger, interior, speakers, etc.) all centered in the middle of the car. Understanding how this works lets you adjust your car accordingly.
Calculus and Vectors can be used to figure out Polar Moment of Inertia, and basic algebra can determine body roll and load transfer, but I will not do that here today because drifting is about technique and you can go to the tuning forum if you need more precise measurements. I'd rather not divulge all of my tuning secrets publicly, either. The two principles I just stated should draw a few conclusions from you, if you read this right so far. First off, adding weight to the center of a car, if the added weight has a greater density than the components of the car, should improve its turn-in speed, it will change direction faster. However, because of additional weight overall, it will have greater load transfer and body roll, and a lower straight-line speed due to a lower power-to-weight ratio. What this means is in tuning certain cars with poor polar moment of inertia, you can improve it by adding weight (or adjusting where your weight is added) by a small amount and achieve greater response in cornering. If a car's transitions are poor, because of the cornering response, this is something you can do. It can improve already heavy drift car's response, but ONLY if those drift cars are sufficiently large enough that it centralizes the mass. A prime example is a 1970 Dodge Challenger. It has 50/50 weight distribution, so adding weight into the middle will not affect its handling, except that it will lower the already wide and relatively lower density car's polar moment of inertia, allowing it to have less resistance in the change of direction it has. Chassis reinforcement on GT5, as well, should reduce the polar moment of inertia slightly, as there is less "give" for the frame of a car to resist the change of motion by strengthening important parts of the car.
While the location of the Center of Mass on an XY plane does affect static (no movement) grip on the tires, it is its "Z axis" location, or how high it is in relation to the tires' contact patch, we are concerned with. The higher the center of mass is, the more pronounced weight and load transfer and thus body roll will be. This means to improve the weight transfer of a lightweight car, instead of adding weight, you can lift the car higher in the air. Cornering speed however, is slightly reduced as because the more weight transfer on the tires from static position, the less overall net grip they will have when cornering at the limit and beyond. This can also be used to help drift cars that get too much grip. This decrease in overall grip at the limit will produce some under-steer as the outside tires have a greater portion of the car's weight on them. This means for heavily over-steering cars, lifting them up into the air on their suspension will help calm them down.
This is unfortunately a very long post to fully explain a few principles, but to sum it up: Weight and Load transfer are different, and controlling them affects your drift significantly. Suspension tuning for camber is related to those, and heavier cars have greater load transfer. Taller cars have greater weight transfer. Taller and heavier cars have greater load and weight transfer. Minimizing this transfer gives you greater net grip, and having a worse weight transfer lowers your net grip. Polar Moment of Inertia affects how quickly a car responds to a change in direction. A lower polar moment of inertia, where more mass is centered around the center of mass, will change direction quickly. You can use the ballast to adjust this, to affect cars that have too slow or too quick changes of direction.
Now then, as promised, a further elaboration of the optimal drift technique I've been working on:
The Brake-Lock drift (as I am calling it for now) involves causing the front wheels to lock, rather than the rear, in a straight line and then uses their excessive slip to begin a four wheel drift that reduces a car's speed faster than a simple lift-off or throw in technique, but reduces it to a less extent compared to an e-brake technique. This causes a moment of four-wheel drift before the accelerator is used. The reason this drift is the fastest is as follows:
1. Because the only weight transfer, initially, is forward and outside, maximum grip from the tires overall is maintained once the drift begins, as the car drifts very flat and maintains higher net grip, and is able to suffer greater G forces around a corner.
2. The wheel that receives the greatest weight is the front-outside wheel. When the drift starts, it must be maintained at a shallow angle or else it will devolve into a slower form of drifting, but an angle at or below the maximum slip angle for the tires will also cause pronounced snap understeer. When controlled, this produces an extremely quick termination of the drift, allowing you to exit corners very very fast, at higher speeds than normal cornering. This is the main reason that the drift is close to grip speeds, when using the slow-in-fast-out technique, because it enters at a higher speed and exits at a higher speed, with minimized loss of in-corner speed. Because of the heavy use of brakes right before the corner, and then the sudden throw-in immediately afterwards, the front-outside wheel's additional weight (and thus grip) pulls the car to the outside. Thus, by adjusting just how much pressure is on that wheel (which is done by modulating how smooth the brake shock and turn-in is), you can easily drift at shallow angles and use its grip to pull your car away from too much oversteer, which would result in a slower drift. On cars with higher levels of weight transfer, this can result in *negative* weight on the other 3 wheels. This means that the wheels are receiving lift forces exceeding gravitational forces on them, and the only thing keeping them on the ground is unsprung weight. In order to properly use this technique, a car must have minimal load transfer, which means having a low polar moment of inertia, as well as a low center of mass AND low G cornering forces, which is why it is optimal for lightweight, smaller cars on low grip tires, but becomes less useful on higher grip tires or heavier vehicles.
Right after the drift begins, the entire car pitches up onto the front outside wheel at the beginning of the turn, which regains traction first as the car begins to oversteer after the initial hard-brake. The reason an E-brake is not optimal, in addition to what I've stated before, is that it does not create this pronounced weight transfer onto this crucial front-outside wheel that will help control your angle, and thus prevent traditional speed loss associated with an e-brake drift. In this, the speed loss once a corner is entered is caused through the turning forces of the car, much like a lift-off style drift, but with the initial shock of the front wheels locking. Another advantage of this technique is that it allows a drifter to use and control higher brake pressure numbers than before.
In order, the car's actions are:
1. Gentle Braking in a straight line
2. Sudden, hard braking in a straight line, front wheels lose traction
3. Gentle trail braking into the corner with sudden turn-in
4. Rear wheels lose traction, 4 wheel drift begins
5. Power is applied to the rear wheels. Front outside wheel regains traction and maintains a shallow angle despite power to the wheels. Weight begins to flatten out as the front inside wheel regains traction fractions of a second later. 4 wheel drift is over, 2 wheel drift begins.
6. Countersteering and normal drift exit procedures, accelerating out of the turn as usual until all four wheels regain traction, first with the front-outside wheel which snaps the car into alignment automatically and allows no wasted time to straighten the car out as it accelerates at max throttle out of the turn early.
However, there are significant limitations to this drift. Because it uses minimal weight transfer to use most optimally, it can rarely be combined with throw-around techniques such as the "Scandinavian flick". It requires a car to be as low to the ground as possible and flat, which means on hills, inclines, and banked corners it becomes a less effective drift and difficulties in maintaining its load transfer become more obvious. For a track such as Tsukuba or Indy, where inclines are minimal, it is very fast. If utilized properly however, it can be used to greater effect downhill than uphill due to the increased weight on the sensitive braking front wheels.
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