5.3: Anti-roll bar basics (Skip Barber F2000), 5.2: Tyre pressures basics (Skip Barber F2000), 5.4: Spring rates basics (Formula Renault 2.0), Additional Terms of Use for Coaching Platform.
A stiffer rear ARB thus reduce available grip at the back while increasing it at the front, hence, making the car more oversteery and less understeery. See if you feel the effect of it, and try to visualise the forces working on the car as you go through the corners. As a result, as soon as one wheel moves up or down, the other wheel is forced to follow that motion. Get the Skip Barber out for a spin, and see if you can adjust the ARB to your liking! Get the Skip Barber out for a spin, and see if you can adjust the ARB to your liking! 500 kg x 1.11 =550 kg (left tyre) The main purpose of the ARB is to change the roll stiffness of the axle it’s installed on, which has two important implications: The ratio of roll stiffness between the front and rear axles affect the balance of the car, especially its tendency to under- or oversteer. Softer rear ARB means more of the lateral load transfer is distributed to the front axle. To understand how balance is affected, we need to understand that as vertical load on a tyre is increased, the coefficient of friction of that tyre decreases. A stiffer rear ARB causes more of the lateral load transfer to be distributed to the rear axle. Additional Terms of Use for Coaching Platform Terms of Use | Controlling how much lateral load is transferred on the front versus rear axle is a balancing act, to optimise how much grip is available at each axle. However, the ARB is essentially a torsion spring which stores some of the energy when twisted, so not the entire movement of one tire is transferred to the other. Let’s work through an example, using the chart above. Vertical load will increase on the outside tires and will decrease on the inside tires.
By multiplying the two numbers, you get the amount of friction force provided by the tyre: If we have a perfectly balanced axle where each wheel is loaded with 400 kg, the total available grip at that axle is: (400 x 1.25) + (400 x 1.25) = 1000 kg (axle). For further explanations on the matter of ARBs, please see the more advanced chapters of this guide, which we’ll publish soon. © 2013 - 2020 Smarty Co. All rights reserved. 300 kg x 1.35 = 405 kg (right tyre) Using the ARB to balance the car Unlike downforce, this is highly relevant for the Skippy. Try to visualise this in your mind. Cornering causes lateral (left/right) load transfer at each axle. After the tyre pressures, which we handled in 5.2, another significant setting to tweak on the Skip Barber is the anti-roll bar (ARB) in the rear. Conversely, softening the rear ARB increases available grip at the back while decreasing it at the front, hence, making the car less oversteery and more understeery. You still get more grip, but proportionally less. This is because the mass of the chassis is not willing to change direction, while the tyres that grip to the surface are. For further explanations on the matter of ARBs, please see the more advanced chapters of this guide, which we’ll publish soon. An ARB can balance this out. The red component in the illustration below is an anti-roll bar, which nearly every racing car has on its rear and/or front axles. 550 kg + 405 kg = 955 kg (axle). Additional Terms of Use for Coaches.
Now we understand how an axle can lose grip under cornering, and is this precisely what causes handling issues. The ARB stiffness can also determine the lateral load transfer between the front and rear axles, even if a car only has one ARB, like the Skippy, which only has one on the rear. Continuing our example, let’s assume that due to lateral load transfer the vertical load on the left tyre becomes 500 kg, while the load on the right side becomes 300 kg.
This can improve the balance of the car, and increase overall grip on the axle as shown in the earlier example. Pricing Relative to the chassis, the left tyres move upwards, the right tyres move downwards, causing body roll. It’s important to note that tuning the ARB will only make a difference if you are utilizing the traction circle, as explained in 3.1. First of all, you need to understand what an ARB is and what it does to the car. To give an example of an ARB’s importance: When a car without an ARB installed goes through a fast right-hand corner, the inertia forces the car to lean to the left side, which is on the outside of the corner. If you ask too much of the car (overall G’s), the ARB won’t help. Academy » iRacing career guide » 5. So while the total load on the axle remains the same (800kg), the total available grip is now only 955 kg. The coefficient on the left tyre decreases from 1.25 to 1.11, while on the right tyre it increases from 1.25 to 1.35. Tuning the rear ARB on the Skip Barber car is mostly a question of driver preference: If you find the car too unstable for your liking, you can try reducing rear ARB stiffness. Just when you need grip the most! See if you feel the effect of it, and try to visualise the forces working on the car as you go through the corners. Privacy Policy | If you find the car unwilling to turn, you can try stiffening the rear ARB. A softer ARB causes less lateral load transfer on its axle, compared to a stiffer ARB. This is known as load sensitivity.
The ARB connects the suspension elements of two wheels on the same axle. At 400 kg of vertical load on a tyre, the coefficient of friction is 1.25. When the available grip of the rear tyres is exceeded first, the car goes into oversteer; when the grip of the front tyres is exceeded first, the car goes into understeer. If you ask too little, you won’t notice any difference in handling.