NASCAR iRacing Series Open Garage: Indianapolis Motor Speedway
July 22nd, 2014 by JaimeB
This just in: Indianapolis Motor Speedway is a 2.5 mile oval. Long straights and four sharp turns provide the qualities of the high speed speedways with the challenge of setting-up the car for braking and corner rotation which will be key here as corner exit is going to play heavily on the cars’ acceleration going into the straights.
Beginning with the stock setup you will find the rear of the car is tight on entry and loose beyond control from middle off. Most of this can be attributed to the weight distribution. In this case they have set the weight all the way back. What this does to the car is pull the center of gravity back like a ball on a pendulum. When the weight is shifted in the corner the ball swings out. Try moving the weight forward 8-11 inches. Start at eight inches and work your way forward, taking note of what the change does to the handling. Do not be concerned if the setup doesn’t feel right; we are just learning about weight distribution and how it affects the car.
You will find that as you move the weight forward it will tighten the car in the middle corner through the exit (exactly where we need it this week). What you are doing as you move the weight forward is pulling that imaginary ball closer to the center of the car. This will help it rotate less and reduce the “loose off” feeling. Moving the weight too far forward will cause the car to push in middle and be tight having what drivers describe as a “plowing” feeling.
“As you move the weight forward it will tighten the car in the middle corner through the exit.”
This leads us to our next adjustment. The caster on the stock setup is obviously an attempt to cope with the over rotation of the car causing it to snap loose. Now that we have adjusted the weight distribution we can pull the front left wheel back and adjust the caster (as we learned in one of our first lessons) to allow the front right wheel to rotate in cooperation through the corner evenly with the left front.
Looking at the tire wear and camber settings we can assume that there is some room to use less of the left front outside and more of the right front inside. Reducing camber in the left front tire will help the loose feeling from the middle off as well as help reduce the tire wear. Since the camber in the right front is conservative we can lean the tire further towards the car (neg) to use the right front more aggressively as well as loosen our car on entry slightly.
While our objective should always be to maximize tire life over the entire tire, we also have to be conscious of what changes to the car’s handling our adjustments will create. Make minor adjustments to the center tire temperature with tire pressure. Once you have the ride height as low as you are comfortable with (spring perch offset) and have the handling close, use a combination of tire pressure, grill tape and track bar adjustments to fine tune the car to your liking.
Our next topic – brake bias – is a common adjustment made on tracks where long straights are combined with tight corners, or any short track where you are using your brakes constantly. Brake bias is best left at the standard (or close) setting ’til the other car handling issues have been addressed so as not to mask handling problems on corner entry.
“Brake bias is simple in theory: The more front brake bias you have the tighter the car will be under braking.”
Brake bias is simple in theory: The more front brake bias you have the tighter the car will be under braking. Once you have the car stable you can adjust the brake bias to assist your car on turn entry. If the car is slightly loose under braking in traffic try adjusting the bias forward just a tad or two to help the wheels brake evenly.
Keep in mind our lessons on ride height as the size and speed of this track can make aero a factor. Try adjusting your tape levels, taking note of the oil and water temperatures. Lowering the car and adding tape can increase the car’s aero quality providing a little extra speed and downforce.
Try taking the car out for thirty laps and making a visual note of the braking cue signs. Try driving further and further into the braking zones and note what happens when you enter the turn too “hot.” Try to find a balance that will give you good corner entry and rotation while setting you up to gain the most possible speed on exit, which is critical for this week’s sim racing at The Brickyard.
Good Luck and God Speed!