CPR Setup Guide

by Jim Getzen

Guide Version: 98.01.07

This section is designed to help people understand the various setup options and how they affect the car's handling. The emphasis here is on keeping the information simple and making it useful. Caveat: I have attempted to base this guide on knowledgeable sources and, in some cases, my own experience. There may be some instances in which the sim responds differently to setup adjustments than reality or theory would dictate, although I am not aware of any such cases. I welcome notification of any errors or useful additions. Please consider this guide a work in progress.

This guide has three parts:
Problems & Solutions section -- designed to solve specific performance problems.
Adjustment by Adjustment section -- each setup item from CPR is explained.
Driver Adjustments section -- describes in-car adjustments.

To get the most out of this guide, it is essential that you understand the following terminology and can relate it to your experience behind the wheel:

Quick Terminology
Oversteer -- The car wants to turn too much - the rear of the car isn't gripping as well as the front.
Understeer -- The car doesn't want to turn - the front of the car isn't gripping as well as the rear.
Turn Entry -- The first part of a corner when the car is braking and turning begins.
Mid-Turn -- The middle of a turn when the car is neither braking nor accelerating and turning is constant.
Turn Exit -- The last part of a corner when the car is accelerating and turning is reduced.
 

Problems & Solutions

The solutions are listed with most effective option first and least effective last. This is very subjective. If "front" or "rear" is omitted then the adjustment applies to both.

Twitchy Car - Soften springs. Soften anti-roll bars. Soften fast and slow bump and rebound. Decrease tire pressure. If twitchy on straights, reduce front wing.

Sluggish Car - Stiffen springs. Stiffen anti-roll bars. Stiffen fast and slow bump and rebound. Increase tire pressure.

Poor Acceleration - Move gear ratios closer together. Set gear ratios higher. Lower rear wing.

Low Top End Speed - Lower rear wing. Lower rear gurney flap. Lower 6th gear ratio if RPMs exceed 14,000. Raise 6th ratio if RPMs don't reach 13,000. Increase tire pressure. Lower front wing. Stiffen springs. Use hard compound tires.

Poor Cornering Speed - Increase wing angles. Soften anti-roll bars. Soften springs, particularly outside springs on ovals. Lower static ride height. Soften tires. Soft slow bump and rebound. On ovals, increase stagger.

Understeer in General - Increase front wing/decrease rear wing (and gurney flaps). Soften front spring/stiffen rear spring. Soften front anti-roll bar/stiffen rear anti-roll bar. Increase camber. Soften front bump and rebound/stiffen rear bump and rebound. Decrease front toe-out and rear toe-in. Move ballast positioning to middle or rear. Decrease front tire pressure/increase rear tire pressure. Increase weight jack (in-car).

Understeer on Turn Entry - Decrease front slow bump. Increase rear slow rebound. Move brake proportioning close to the rear.

Understeer Mid-Turn - Soften front spring/stiffen rear spring. Soften front anti-roll bar/stiffen rear anti-roll bar.

Understeer on Turn Exit - Increase front slow rebound. Decrease rear slow bump. Soften front spring/stiffen rear spring. Soften front anti-roll bar/stiffen rear anti-roll bar.

Oversteer in General - Decrease front wing/increase rear wing (and gurney flaps). Stiffen front spring/soften rear spring. Stiffen front anti-roll bar/soften rear anti-roll bar. Decrease camber. Stiffen front bump and rebound/soften rear bump and rebound. Increase front toe-out and rear toe-in. Move ballast positioning to middle or front. Increase front tire pressure/decrease rear tire pressure. Decrease weight jack (in-car).

Oversteer on Turn Entry - Increase front slow bump. Decrease rear slow rebound. Move brake proportioning close to the front.

Oversteer Mid-Turn - Stiffen front spring/soften rear spring. Stiffen front anti-roll bar/soften rear anti-roll bar.

Oversteer on Turn Exit - Decrease front slow rebound. Increase rear slow bump. Stiffen front spring/soften rear spring. Stiffen front anti-roll bar/soften rear anti-roll bar.

Poor Braking - Move brake proportioning so all four tires lock up simultaneously.

Can't Turn During Braking - Move brake proportioning closer to the rear.

Car is Bottoming Out - I haven't found out yet how to tell if the car is bottoming out in CPR; if you have, let me know. Nevertheless: increase ride height. Increase 3rd spring rate. Decrease freeplay (I think). Stiffen springs. Increase fast and slow bump.

Car Doesn't Win Races - Increase practice time. Increase setup knowledge. Increase track knowledge. Increase practice time. Reduce skill setting. Reduce quality of human opponents. Increase practice time. Resort to using driving aids. Get used to the view of a rear wing.
 

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Adjustment by Adjustment

This section is laid out in the same manner as the garage tabs in CPR, although of course the Overview and Pit Strategy tabs are omitted.

Aerodynamics

Front Wing Angle (can be changed in the pits) - The front wing controls how much downforce is applied to the front wheels when the car is moving. It has little effect on the car in slow corners. Too much front wing causes oversteer and can make the car very twitchy at high speeds. Too little front wing in relation to the rear wing causes understeer. Increasing the front wing does not significantly slow down the car on the straights.

Rear Wing Angle - The rear wing controls how much downforce is applied to the rear wheels when the car is moving. It has little effect on the car in slow corners. Too much rear wing in relation to the front wing can cause understeer. Too little rear wing causes oversteer. Increasing the rear wing does significantly slow down the car on the straights.

Gurney Flaps (can be changed in the pits) - The gurney flaps are tabs attached to the front and rear wings. They are used to make small adjustments to the front and rear wings. For example, increasing the front gurney flap is like making a small increase to the front wing angle.

While the front wing itself can be adjusted in the pits during a race, the rear wing cannot, making the rear gurney flap the only way to adjust the rear wing mid-race. However, rear gurney flap adjustments are not allowed during oval races.

Static Ride Height - This is the ground clearance of the car when it isn't moving. In general, you want to set the ride height as low as you can, but not so low that the car bottoms out due to bumps and chassis movement. This setting is related to the Third Spring Rate and Freeplay settings. The lower the ride height, the more downforce the car will generate. In CPR, setting the rear ride height low and the front ride height high seems to allow quicker acceleration and higher top-end speeds.

Drive Line

Gear Ratios - The gear ratios affects how quickly the car accelerates and the top speed it can attain. While there is great deal of discussion, strategy, and fine tuning one can apply to the gear ratios, here is a simple three-step process for setting up the gears:

1. Find the slowest corner on the track and adjust the 2nd gear ratio so that it when you are just starting to accelerate out of the corner, the RPM's are in the middle/lower part of the band, say  9,000 to 10,000 RPM. If the gear ratio is set too high, then the RPMs will be too high, causing you to have to shift immediately to a higher gear. If the gear ratio is set too low, you will be "bogged down" in 2nd gear and will accelerate too slowly. Once you play around with higher and lower settings, you will see what I mean and will find an appropriate setting. Why set 2nd gear to the slowest corner instead of 1st gear? Save 1st gear for getting started from a stopped position. This is a luxury that you have with 6 gears instead of the 4 gears in some race cars.

2. Find the fastest point on the track (usually right at the end of the longest straight). Set up 6th gear so that you reach 13,000 or 14,000 RPMs at the fastest point. One "notch" from the end of the RPM band display is 14,000 RPM. You can change the Pi Display Setup so that it displays actual RPMs instead of MPH if it doesn't already. If 6th gear is set too high, then you will reach the end of the RPM band too soon and will sacrifice top speed. If 6th gear is set too low, then your acceleration will suffer.

3. Setup the rest of the gears so they are nicely spaced in between 2nd gear and 6th. I say "nicely" instead of "evenly" since the spacing between gears generally gets smaller and smaller as you move up the gears. For example, the difference between 2nd and 3rd gear might be 3.0, but the difference between 5th and 6th gear might only be 0.6. When you are accelerating, if you find that moving to a higher gear bogs down the car (RPMs are too low), then you need to decrease the distance between the two gears.

Final Drive Ratio - Changing the final drive ratio is the same as changing all the other gear ratios at once. It is used to make coarse adjustments to all gear ratios simultaneously. In general, you can forget about this setting unless you find yourself near the bottom of the possible range of 6th gear values (say less than 2.0). In that case, lower the final drive ratio.

Differential Type - Use Locked Differential for ovals and Limited Slip Differential for road and street courses. It is that simple.

Tires

Compound (can be changed in the pits) - The tire compound is the material and style of the tire. Rain tires are grooved and, of course, should always be used in the rain. Soft compound tires have the better grip than hard compound tires but wear out faster. Hard compounds can provide higher top speeds. In general, always use soft compound tires on road and street courses. For high speed ovals like Michigan and Fontana, hard compounds are probably a better choice than soft, particularly for the outside tires which take the more punishment than the inside tires and wear faster. For smaller ovals like Milwaukee, grip is everything, and so soft compounds might be a better choice.

Pressure (can be changed in the pits) - Higher tire pressure yields a more responsive car and a higher top speed, but the grip will suffer and the car can get too twitchy. Too little tire pressure can make a car "wallow" and sluggish. Tire pressures are generally lower on road and street courses than ovals. Too much front tire pressure in relation to the rear causes understeer, while too little front pressure creates oversteer. With regard to ovals, increasing the inside tire pressures adds oversteer, while increasing the outside pressure creates more understeer.

Rear Stagger (can be changed in the pits) - If the right side tires are larger than the right side tires, then the car has positive stagger. This helps the car turn left and is great for ovals, but is not used on road and street courses. Too much stagger will cause oversteer while too little can cause understeer. If you notice than your car tends to pull to the left on straights, then you have noticed stagger in action.

Suspension (Axle)

3rd Spring Rate - The 3rd spring is used to limit vertical suspension travel and is related to the ride height. A stiffer 3rd spring keeps the car from bottoming out and allows the use of a lower ride height. 3rd springs are not used on ovals. My recommendation: set both the front and rear 3rd springs to 3000 ppi and forget about them until you become an expert at setting up a car.

Freeplay - The freeplay setting's effect on handling is a bit of a mystery. The freeplay determines how much the suspension travels before the 3rd Spring goes into action. Freeplay is not used on ovals. My recommendation: set both the front and rear freeplay to 0.2 inches and forget about them until you become an expert at setting up a car.

Anti-Roll Bar - Also known as sway bars, these control the degree to which the chassis of a car "rolls" (tilts) in a corner. Softer anti-roll bars produce better grip but make the car sluggish. Stiffer anti-roll bars provide tighter chassis control but at the expense of grip. A front anti-roll bar which is soft in relation to the rear causes oversteer mid-corner. A soft rear anti-roll bar in relation to the front adds understeer mid-corner and can help prevent over-steer at the turn exit (when power is applied).

Toe-Out - This setting controls the angle of the front wheels to each other. If the front wheels are exactly parallel, then toe-out is zero. More often, the fronts of the wheels are angled outward slightly. Too much toe-out gives understeer, while too little can induce oversteer. Like camber, it is hard to know when you have the right settings. Experiment, and if you aren't sure, try 0.06 inches.

Toe-In - This is similar to toe-out, but in the case of the rear wheels, the front of the wheels is angled inward instead of outward. Again, too much toe-in causes understeer, while too little provides oversteer. Less toe-out, particularly on the rear wheels, is used at ovals. Experimentation is necessary to get the right feel. If you don't want to mess with this one, try 0.08 inches and move on.

Steering Ratio - This is an easy one -- it controls how tight of a turn the car can make. My preference is to set the steering ratio at the lowest setting which will allow me to take the tightest turn on the track. For ovals with big turns, a setting of 5 to 7 might be best, while Long Beach, which has a very tight hairpin, requires a setting of 11 or higher. The higher the setting, the more sensitive and twitchy the car will be to your steering input.

Suspension (Corner)

Spring Rate - The springs determine how the weight of the car is distributed on the four tires. Softer spring settings will increase the grip of the car, but make it less responsive.  Front springs which are too stiff in relation to the rear springs causes understeer mid-corner. Rear springs that are set too stiff compared to the front causes oversteer mid-corner.

Camber - When the top of a wheel is tilted toward the center of the car, the wheel has negative camber. Camber means tilt, and it helps the car turn in the direction of the tilt. Hence, you see significant negative camber on the right side wheels on ovals. Sometimes, even the left side will tilt to the left on an oval (positive camber). On road courses, both sides of the car should use negative camber.

Without temperature readings from the inside, middle, and outside of the tire, it can be difficult to know what the proper camber setting is for a particular tire. You will have to experiment. Too much or, more likely, too little camber will give less than optimum grip in a corner. In general, braking is better when camber is closer to zero since most braking occurs when a car is going straight -- low camber means that more of tire is contacting the road and available for braking grip.

Suspension (Damping)

Dampers are shock absorbers and work in conjunction with the springs to control the up and down movement of the wheels. The bump setting controls the resistance to the upward movement of the wheel, while the rebound settings changes resistance to the downward movement.

While the various combinations of bump and rebound settings can get very complicated, the basic adjustments are discussed below. There are more specific sets of adjustments tailored to the location of the understeer/oversteer (turn entry vs. turn exit). See the Problems & Solutions section for information on these special situations.

Fast Bump/Fast Rebound - The fast settings are used to smooth out sudden bumps in the road (fast movements of the wheels). Softer settings provide a smoother ride. Softening the rear fast bump/fast rebound in relation to the front increases understeer over bumps.

Slow Bump/Slow Rebound - While the spring rate determines the handling of the car mid-corner, the slow bump/slow rebound settings affect the handling at turn entry, turn exit, and during slower elevation changes. If the front slow bump and slow rebound are set too low in relation to the rear, the car will tend to oversteer in turns. On the other hand, if your car is oversteering, increasing the front bump and rebound in relation to the rear can help. See the Problems & Solutions section for information on special situations.

Miscellaneous

Brake Proportioning - This setting determines how hard the front brakes work in relation to the rear. Ideally, under heavy braking all four tires should lock-up simultaneously. A higher brake proportioning (70% maximum) setting moves more work to the front tires, causing them to lock up first. A lower setting (50% minimum) will cause the rear tires to lock-up first. Many people err on the side of the rears locking up first since the front tires will still be able to steer the car into a corner. If you are a heavy braker, then you may need to move the proportioning closer to the front (higher) since more of the weight of the car will be on the front tires -- the front brakes will have to work harder than the rear before locking up. By the way, in CPR you can see the front brakes locking up -- the front tires stop rotating.

Fuel (can be changed in the pits) - The more fuel you have, the more the car will tend to understeer. Trying setting up the car with a moderate fuel load such as 20 gallons. That way, the behavior of the car with either higher or lower levels of fuel shouldn't be dramatically different than your "ideal" behavior. A car with only a few gallons of fuel can accelerate, brake, and corner faster than a car with a full tank. Therefore, only take on as much fuel as you need to finish the race.

Mirrors - Increasing the left mirror angle and decreasing the right mirror angle will provide a wider view of the action behind you, but may limit the view directly behind the car. Set the mirrors to your liking once and then forget it -- who cares what is happening behind you anyway? ;-)

Ballast Positioning - Champ cars are required to weigh a certain amount, necessitating that extra weight be added to the car. This weight can be added to the front of the car (which adds understeer), to the middle of the car (which is neutral), or to the rear of the car (which adds oversteer). For most situations, I recommend leaving it at the middle. Then, if you need extra help with understeer or oversteer, adjust it accordingly.

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Driver Adjustments

From within the cockpit, a driver can make two adjustments related to fuel economy and three adjustments to help counteract changes in the car's handling due to a lighter fuel load, worn tires, temperature changes, and so on. Keep in mind that these are fine-tuning adjustments -- they won't be able to fix serious problems with the car setup.

Handling Adjustments

Brake Bias (defaults to 0.5, hitting the "1" key decreases it to a minimum of 0, hitting the "2" key increases it to a maximum of 1) - Increasing the brake bias moves the brake proportioning closer to the front, causing the front wheels to lock up sooner, in relation to the rear. Moving the bias backward (lower) causes the rear wheels to lock up sooner.

Weight Jack (defaults to 0.0, hitting the "7" key decreases it to a minimum of -1, hitting the "8" key increases it to a maximum of +1) - The Weight Jack driver adjustment is essentially a ride height adjuster that allows you to change the relative corner weights of the left rear wheel and right front wheel. With a low fuel load, a car may begin oversteering. You can compensate by increasing the weight jack, adding more weight over the right front wheel. On the other hand, with a full tank, a car will tend to understeer. Decreasing the weight jack has the effect of moving more weight to left rear wheel, which can help eliminate understeering.

Front Anti-Roll Bar (defaults to 2, hitting the "7" key cycles it through a range of 0-4) - If the car is understeering in the corners, soften (decrease) the front anti-roll bar with a setting of 0 or 1. If it is oversteering, increase the front roll bar to 3 or 4.

Rear Anti-Roll Bar (defaults to 2, hitting the "8" key cycles it through a range of 0-4) - If the car is understeering in the corners, increase the rear anti-roll bar with a setting of 3 or 4. If the car is oversteering, decrease the rear roll bar to 0 or 1.

Fuel Economy Adjustments

Fuel Knob (defaults to 6, hitting the "3" key decrease it to a minimum of 0, hitting the "4" key increases it to a maximum of 11) - The fuel knob controls the rate of fuel flow to the engine. To conserve fuel, decrease the fuel flow at the expense of engine performance. On the other hand, if fuel conservation is not needed, it might be tempting to increase the fuel flow to its maximum to gain engine performance. It doesn't work that way. Above a setting of about 8, performance seems to decrease since more fuel is being sent to the engine than it needs to work efficiently. In informal experimentation, a setting of 7 seems to provide the best performance, although the default setting of 6 yields practically the same results.

Boost Knob (defaults to 5, hitting the "5" key decreases it to a minimum of 0, hitting the "6" key increases it to a maximum of 11) - The boost knob can be seen on the left side of the dashboard and controls the turbo boost pressure. Champ cars have a pop-off valve which limits the turbo pressure to 40 psi. If that level is exceeded, the valve gives way, causing a drop in engine performance and emitting an unmistakable sound. To conserve fuel, decrease the boost knob. There is no way to increase the boost knob above its default setting of 5 without blowing the pop-off valve. If you are not low on fuel, then leave the boost knob on 5.