NR2003 - The Chassis, an in-depth look at setting up your race car (DRIVETRAIN/AERO)

So here it is, the NR2003 stripped down chassis. If you have a few minutes (ok .. hours) read on. I'm going to go through the entire chassis and try to explain the best I can, what everything does and how to adjust it to your specific driving style.

I've spent quite a few hours compiling the information you are about to find on the following pages. Most of it was found on the internet at various racing sites and some from fellow driver's here at NBVRL. So please don't send me a ton of e-mail's telling me I pirated it, I'm telling you up front where all the info came from :) I've simple re-arranged it, explained some in more detail, simplified some and added quite a few pictures taken from NR2003 or rendered by myself in 3DS Max. All that being said ..... ENJOY !

The information in this guide may change without notice. I've tried to make this guide simple to use & easy to understand. By clicking on the contents you will be taken directly to the info your looking for. Throughout this guide I will use the abbreviations RF,RR,LF,LR. These stand for right front, right rear, left front, & left rear respectively. Whenever I bring up the left or side of the car I'm talking about the drivers side. The right side of the car is the passenger side. All left & right references are viewed from the drivers position. By holding your mouse over a setup option for a few seconds in the sim, you will be given a brief description of how that adjustment works or what it affects. Right clicking an option brings up the description right away.

One last thing I must mention before turning the wrenches. It is important to understand that for every adjustment you attempt, it may not produce the desired results right away as mentioned below. You may have other chassis adjustments that are not quite right masking the problems your trying to adjust for. Because of this factor, you may not see as drastic a change in your adjustments after just one change. You may have to readjust another chassis component to so call "free" up your original adjustment. If you feel your setup is close, yet seems to be lacking that one minor adjustment, it may be more involved that just adjusting one more component. You may have to "undo" another few adjustments elsewhere then go back to your original adjustment to get it just right. For every action you take, there will be a counteraction that may not appear at first to be in the best interest of your setup. There may be times when you may have to take two steps back to gain one step forward. Because of this, chassis adjustments can become frustrating to figure out. It isn't easy, as many Sprint Cup teams find out on any given Sunday. Perseverance & patience are required when playing this chassis setup game.


FRONT BIAS

The Front bias can be adjusted by clicking the weight bias tab on the garage screen. Front bias is the amount of weight on the front of the chassis as compared to the rear of the chassis. Front bias is determined by placing lead weight at various points as low as possible in the chassis. Sliding this weight forward gives you more front weight or bias. Sliding this weight towards the back of the car decreases front bias & increases rear weight or bias.

The most front bias were allowed is 54.2% (1950 lbs.) The least amount is 45.8% (1650 lbs.) Finding the correct amount of front bias depends on the track, banking, spring rates, frame heights & gearing. Generally speaking, the flatter the track, the more front bias required. The higher the banking the less front bias required. This is because the higher banked tracks require less braking which in turn means less weight is being transferred to the front of the vehicle. Less front bias or more rear bias would be preferred at a track like Talladega.

A slower track that requires shorter gear ratios, will also require less front bias. This is due to the problem of wheel spin that can occur during acceleration. You would rather have less front bias or more rear bias to help transfer weight to the rear quicker to avoid wheel spin. Just the opposite would be true when a higher gear ratio is required.

The more front bias you run the tighter the chassis will be, especially at mid turn & beyond. The less front bias you run the looser the chassis will be. A front bias of 50 - 51% would be a good starting point for many tracks. A track that is small & requires heavy braking may only require a front bias of 48 or 49%. Anything below 48% or higher than 51% isn't realistic in a real cup car, but can still be effective given different spring rates, sway bars & frame heights. Experimentation once again with all these variables will be the only way to correctly determine the proper front weight bias given the various circumstances.

Another factor that must be considered when dealing with front bias is Fuel. As fuel is burned, your rear weight distribution is lowered. You will lose approximately 1% of rear weight per every 5 gallons burned. This means that by the end of a full fuel run you'll lose over 4% rear weight. With less fuel & less rear weight, the car will have a tendency to tighten up as fuel diminishes. Although your not directly changing your front bias, you will be affecting the amount of weight that is being transferred as fuel is burned. This will result in an ever changing car as fuel dissipates.


Front Bias Adjustment Guide

More front bias will tighten the chassis.

Less front bias will loosen the chassis.


LEFT BIAS

The left bias can be adjusted by clicking the weight bias tab on the garage screen. Left bias simply means how much weight is on the left side of the car compared to the right side. Between all the weight adjustments allowed, this one is the easiest to figure out.

When you enter a corner on an oval track, you hit the brakes & turn left. Weight will naturally go forward & to the right upon corner entry. Because of this you'll want to start with weight percentages greater on the left side & towards the rear. When you start with more weight to the left & rear, your hoping to balance the weight equally when you enter the corner once weight is transferred. If you could run your car, with the weight being equal at all 4 corners entering a turn, then you would run faster than anyone else in the corners. With perfect weight distribution you would have perfect tire temperatures. Perfect tire temperatures equals the maximum traction you could attain. This is what were all trying to accomplish with every single adjustment we make on a racecar.

Finding the overall correct weight distribution isn't easy & varies with every track. As heavy as WC cars are, left side bias on an oval is simple to deal with. Always keep as much weight as possible towards the left side of the chassis. Within NASCAR Racing we are allowed left bias adjustments from 54.2% left side weight, to 45.8%. Whenever your dealing ONLY with left hand turns, always keep the left side weight at 54.2%. More left side weight allows you to take left hand turns at a higher speed.

The only reason you would want to adjust the left side bias is when you're dealing with both left & right hand turns. These obviously would be the road courses. You'd probably want to run an even left bias of 50% at these tracks. Although at a track where there are more right hand turns than left, you may favor a higher right side percentage. This will allow you to get through those right handers a little more quickly, but at the sacrifice of losing speed going through the left handers. This still could be advantageous if there are few more turns going right than left.

Left Bias Adjustment Guide

Higher left side bias will help turn the car left into a corner & loosen a chassis when making left hand turns.

Higher right side bias will cause the car to Understeer when making a left hand turn.


WEDGE

The wedge can be adjusted by clicking the weight bias tab on the garage screen. Wedge is also known as cross weight or diagonal weight. Wedge is the total weight of the RF & LR corners divided by the cars total weight. Wedge is used to keep the back of the car tight entering a corner while also adding bite exiting a corner.

Within NASCAR Racing, wedge can be adjusted as low as -150lbs. (47.9%) to as high as 150lbs. (52.1%).

The total amount of wedge required depends on track size & roll couple in the car. A setup that will spin it's tires easily will require more wedge to counter act the traction loss under power. A setup with a higher gear ratio or one that does not spin the tires will require less wedge. Wedge is required to get through the corners. Excessive amounts of wedge can slow the car down & wear the RF & LR tires prematurely.

Where as changing the front & left side bias is done by moving lead ballast, changing the wedge is done by screwing up or down on load bolts located over the RF & LR springs. You might think that by changing wedge you would change left side or front bias, but that isn't the case. No matter how you adjust the wedge the left & front bias will always remain the same. Increasing wedge will tighten the chassis. Decreasing wedge will loosen the chassis.


Wedge Adjustment Guide

Increasing wedge tightens the chassis.

Decreasing wedge loosens the chassis.


STEERING RATIO

Steering ratio is the difference in how many degrees your front wheels are turned compared to how many degrees your steering wheel is turned. Steering ratio is measured by dividing the number of degrees the tire is turned into the number of degrees the steering wheel is turned. If for example you turn your steering wheel 180 degrees & your front tires were to turn 10 degrees you would have a 18:1 steering ratio. (10 into 180 = 18)

Your steering ratio adjustments range from 12:1 to 32:1 within NASCAR Racing. The lower the ratio (12:1) the quicker the steering response. You'll notice that using a lower steering ratio will require less turning of the wheel to negotiate a corner. This low steering ratio can result in a twitchy car since the smallest of steering inputs will be felt in the car. It is very easy to over steer a car with such a low steering ratio.

A car with a higher steering ratio (32:1) will require more steering input to get through a corner. Too high a steering ratio might give the feeling of a tight race car as you find yourself turning the wheel further to negotiate a turn. This isn't a push, it's just requiring more movement in the wheel to steer the front tires the same amount as with a lower ratio. With a ratio of 12:1 at a track like Michigan you might only have to turn the steering wheel 45 degrees to the left to get through the corner. With the same exact setup, but a ratio of 32:1 you might have to turn the wheel 90 degrees or more to the left to negotiate the same exact corner.

There is no correct setting for steering ratio. It all depends on the driver & what he is comfortable with. A lot of this depends on the type of steering device used. With so many different wheels on the market, you wont know what is comfortable for you until you experiment with it yourself. You may be comfortable with a steering ratio of 24:1 at Dover with a TSW brand wheel, but find that after using a MadCatz wheel that the ratio is all wrong. This is because some wheels turn more or less degrees than others requiring different steering ratio settings.

As a general rule of thumb, the smaller the track & tighter the radius of the turn, the lower the ratio you'll want to run. Road courses are a track with slow sharp turns that would require a lower ratio. High speed long sweeping corners would not require such a low steering ratio since you are not required to turn as sharply on tracks like these.


Steering Ratio Adjustment Guide

The lower the ratio the quicker the steering response.

The higher the ratio the slower the steering response.

Lower ratios require less turning of the wheel to negotiate a corner.

Higher ratios require more turning of the wheel to negotiate a corner.