As a wannabe race car engineer who enjoys driving stock spec street cars in Assetto Corsa, I often wonder why some cars handles so good and some cars behave kind of odd.
There are certainly many many variables that contribute to the characteristics of a car, such as front to rear spring/wheel rate, alignment spec, but perhaps there is something that is a little more fundamental to those: the center of gravity height.
I did a quick survey of the baseY values, in suspension.ini, in some of the unpacked data files in my Assetto Corsa directory and found something interesting. This is by no mean a thorough comparison, but it does reveal a few things:
The obvious thing is that the Formula cars such as Lotus 25 has the CG at about at the center of the wheel: BaseY= 0. Low CG height in formula car means the car has low ride height, and the body height is low, unlike the hatchbacks. In the other end of the spectrum, the baseY specification on salon cars such as Kuno’s Escort RS1600 is -0.25m and Abarth 500 at -0.25/0.24 m. If all cars have the same size tires, then the BaseY value can be used to directly compare their CG height. But that is not the case. (And then if a car is lowered, seems typically baseY is not changed but only the rod_length is changed to raise or lower the car. That means the chassis/suspension definition is consistent and not changed.)
One of the effect of low CG height is that the chassis rolls displacement is less by the lateral force created by the friction of the tires. The distance between the CG height and the road surface or the tire contact is the leverage arm. Thus at a given lateral force, a car with greater CG height will create greater torque about the CG. Although theoretically roll typically create lower ultimate friction, and create positive camber on the tires. But I feel that realistically the roll is one of the ways a sim driver can sense the car’s response to the input. For a road car to feel real, I strongly feel the need to have some roll motion when a car goes through corners.
From this perspective, the reason why some cars felt “off” to me became apparent. A few mod cars stick out like a sore thumb. Mods such as a Ford Focus WRC, Fiesta ST mod and a Golf GTI have BaseY, have baseY lower than 0.12 m, while most hatchbacks’ numbers are typically above 0.20 meter, many around 0.24 meters. These cars, with low baseY value , drove kind of without much feel, now I think I know why.
I understand that other variables such as high wheelrate or high ARB rate will also lead to similar feel. But even with a reasonable wheelrate/ARB rate, a low CG height will definitely reduce the roll and take away from my enjoyment of driving a street spec car in AC.
I do hope that mod designers can generally get the baseY value in the right ball park. So that we all get to enjoy nice driving street cars.
There are certainly many many variables that contribute to the characteristics of a car, such as front to rear spring/wheel rate, alignment spec, but perhaps there is something that is a little more fundamental to those: the center of gravity height.
I did a quick survey of the baseY values, in suspension.ini, in some of the unpacked data files in my Assetto Corsa directory and found something interesting. This is by no mean a thorough comparison, but it does reveal a few things:
The obvious thing is that the Formula cars such as Lotus 25 has the CG at about at the center of the wheel: BaseY= 0. Low CG height in formula car means the car has low ride height, and the body height is low, unlike the hatchbacks. In the other end of the spectrum, the baseY specification on salon cars such as Kuno’s Escort RS1600 is -0.25m and Abarth 500 at -0.25/0.24 m. If all cars have the same size tires, then the BaseY value can be used to directly compare their CG height. But that is not the case. (And then if a car is lowered, seems typically baseY is not changed but only the rod_length is changed to raise or lower the car. That means the chassis/suspension definition is consistent and not changed.)
One of the effect of low CG height is that the chassis rolls displacement is less by the lateral force created by the friction of the tires. The distance between the CG height and the road surface or the tire contact is the leverage arm. Thus at a given lateral force, a car with greater CG height will create greater torque about the CG. Although theoretically roll typically create lower ultimate friction, and create positive camber on the tires. But I feel that realistically the roll is one of the ways a sim driver can sense the car’s response to the input. For a road car to feel real, I strongly feel the need to have some roll motion when a car goes through corners.
From this perspective, the reason why some cars felt “off” to me became apparent. A few mod cars stick out like a sore thumb. Mods such as a Ford Focus WRC, Fiesta ST mod and a Golf GTI have BaseY, have baseY lower than 0.12 m, while most hatchbacks’ numbers are typically above 0.20 meter, many around 0.24 meters. These cars, with low baseY value , drove kind of without much feel, now I think I know why.
I understand that other variables such as high wheelrate or high ARB rate will also lead to similar feel. But even with a reasonable wheelrate/ARB rate, a low CG height will definitely reduce the roll and take away from my enjoyment of driving a street spec car in AC.
I do hope that mod designers can generally get the baseY value in the right ball park. So that we all get to enjoy nice driving street cars.
