iRacing Blog – 2/2/15 What goes into preparing an iRacing car for a race?

The Gen 6 Cup car is the model used for NPAS. Throughout the year, iRacing updates the model to keep the car as accurate as the real-world cars. Prior to each race, iRacing provides the weather conditions for race day with the temperature, wind conditions, and whether it will be cloudy or sunny. All of this affects the set-up needed for the car.

What goes into preparing an iRacing car for a race?  If you think it’s just about turning the computer on and hooking up a steering wheel and pedals – think again.  Here’s just some of what goes into setting up a car for one race.

The biggest thing to think about in setting up the car is how everything works together. How one change will affect another change and the overall feel of the car. In iRacing we are able to change anything the real teams can in the suspension of the car. From simple adjustments such as:

The steering box which just adjusts the amount of wheel input needed to turn the wheel a certain amount.

Tape controls the temps of the motor and more tape over the grille opening will increase the counts of downforce on the car and give the car more aero grip rather than mechanical grip.

Brake Bias is an adjustment that can be made in the garage as well as in the car, can help settle the car under braking by adjusting the amount of front or rear brake in the car, ultimately used to fine tune a car during the race.

To “bigger” adjustments, used to achieve the best combination of aero and mechanical grip which changes from track to track. Again, each and every one of these adjustments affects the cross weight and overall feel of the car as well as working with one another at every point on the racetrack. At a short track (less than a mile) aero means less than the mechanical grip in the car. But, at an intermediate to superspeedway (greater than 1 mile) aero grip is focused on more heavily than mechanical most of the time do to the high speeds; anywhere from 170-210mph:

Cross weight – Percent of vehicle weight on the left rear and right front tires.

Spring perch offset, adjusts the height at which the spring is installed in the chassis, used to adjust ride heights and the travel of the chassis through the corner.

Spring rate or how stiff the spring is, springs we use ranges anywhere from 300-10,000 lbs/in in the front and 200-10,000 lbs/in in the rear. Springs are the most important adjustment on these cars to make them work the way we want. From determining the travel we need to “seal off” the car (minimize the space between the chassis and the track) to gain maximum aero grip, to controlling the amount of body roll in the setup in order to control tire wear. Along with the springs, shocks (Bump and Rebound stiffness of the shocks) help the most with tire conservation and holding the chassis to the track and keeping the car from hitting the track but getting as close as possible. Packers change the height of the bumpstop on the spring to change where in the corner or travel of the spring, the setup hits the bumpstops to where the car does not travel any further.

Camber / Caster control the position or lean of the tires, which is used the obtain the maximum contact patch from the tire to the racing surface.

Sway bar, controls body roll through the corners to adjust corner weights of the 4 corners of the car.

Toe-in / Toe-out, mainly controls tire wear and straight-line speed/stability. Toe-in means the tires are steered toward each other, negative Toe-in or Toe-out means the tires are steered away from each other.

Truck arms, hold the rear axle in place longitudinally and have moveable mounts on the chassis in three variable positions.

Track bars, hold the rear axle in place laterally and can be easily changed for small adjustments to fix handling in specific areas either entry or exit of the corners.

Lastly, gear ratio. Usually given two or three choices of gear from 3.60 – 6.50 by NASCAR which changes from track to track.

There’s much more to change with respect to everything in the garage but these are just a few.

Every change works with one another and each change in one area will change something in another area of the car. Each little thing will make a difference and the slightest change could mean the difference between winning and losing.


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