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THE RACERS EDGE 10-01-00

OVAL TRACK SETUP - Part Two
A Beginners Guide To Oval Racing

By John Nuttall - Raceway Kart Association

In the second part of this Special Report designed for the beginner, I will be discussing the following topics for basic oval track setup for both pavement or dirt. The topics are:

· Positioning the seat
· Scaling and adjusting weight
· Basic adjustments you can make at the track

Note: In Part One, I discussed selecting and aligning wheels and tires, and understanding weight and balance. Part One can be found in the Archives section.

The Seat. The next step in setting up your oval track kart is installing the seat. It is important to remember that the weight distribution of your kart changes depending on where you place your seat. The driver is usually the heaviest part of the kart. Take your time to analyze this important step. Here are some significant things to keep in mind.

The rear of the seat back cannot go behind the center of the rear axle. Most tracks have a minimum seat back height. In most cases, the driver should be sitting to the left of the kart’s centerline. This helps give the kart left hand weight. A larger percentage of the driver’s weight should be on the left rear tire. This helps increase cross weight and keeps the left rear tire on the track. Note: If you have a straight-up kart with the seat mounts welded in place, you will not be able to do this.

Remember, when you add weight you will want to start at the left rear corner of the kart.

Place a sheet of plywood under the frame of the kart (without the wheels on the kart). Set the seat on the plywood. This will make the seat the same height as the bottom of the frame. Now, have the driver sit in the seat and find a comfortable sitting position for the drivers arms and legs. Mark the seat position. Drill the necessary holes in the seat and begin bolting it in that position. (Note: Don’t get too excited as you may want to move the seat after you scale the kart).

As a general rule, the seat should be to the left of the centerline of the kart. The seat must be inside the frame rails, and the back of the seat should be in front of the center of the rear axle. In this position, the driver can easily reach all controls and feel comfortable.

Scaling the kart - The basic setup. Before we discuss the actual methodology, I need to explain how to figure weights and percentages. The math is very simple. First, you will need the weight of each corner of the kart with the wheels and tires on the kart. Second, total the corner weight.
Model:
               Front Weight: Right Front + Left Front = 100
               Cross Weight: Right Front + Left Rear = 100
               Left Side Weight: Left Front + Left Rear = 100

Note: The manufacturer of your kart should have a setup sheet for different types of tracks and what percentage work best for your kart. If you kart did not come with a weight sheet, ask for one. It should be part of the service they sold you.

Weight Percentages:
               Front: 43% - 45%
               Left: 54% - 56%
               Cross: 52% - 54%

Example: If you are racing Briggs Light at 305 lbs., your approximate corner weights should be as shown:
               Left Front = 68 lbs.
               Right Front = 68 lbs.
               Left Rear = 95 lbs.
               Right Rear = 74 lbs.

Front Weight: 68 +68 = 136 lbs. or roughly 44% of 305 lbs.
Cross Weight: 95 + 68 = 163 lbs. or roughly 54% of 305 lbs.
Left Side Weight: 95 + 68 = 163 lbs. or roughly 53% of 305 lbs.

This is a good setup starting point to take to the track.

Now, to scale your kart. Scaling the kart can be done with the new computerized scales or with four simple bathroom scales. A new computer scale will sell for as little as $1000 up to $2500. Bathroom scales can be purchased at a discount store for as little as $20 each ($80 for four). Note: If you do use bathroom scales, make sure they are the same brand and the same height. Also, make sure they all weigh the same. Test each by setting them on the floor and standing on them. Do this until you find four scales that weigh the same.

Important: The spot you use to set up the kart needs to be level. Use a 6 ft. long carpenters level to make sure your scales or pads are level. Your scales must also be the same height as well. Floor tiles make good shims to adjust the height of the scales. Mark the four spots on the floor; 1,2,3,4 and the scales, too. This can make scaling easier the next time.

The driver must now sit in the kart, with his/her helmet on in a normal driving position. The driver should not try to look at the scales. Moving the driver’s head over the outside of the kart will change the reading on the scales.

How to move weight on a kart. Take some time to make adjustments to the kart to see what they do to the corner weights. Moving a washer on the front spindle will change the corner weight. Now is the time to find out how much.

Front Weight. What does front weight do? Front weight controls how well the kart turns. More weight on the front wheels gives the kart more turning traction. Front weight also takes away traction from the rear wheels. If you add too much front weight the kart becomes loose.

How do you get more front weight? 4 Ways: 1) The front of the kart can be lowered by moving the washers on the kingpins (lowering the front of the kart adds front weight), 2) Moving the tires in on the spindles (This also lowers the front end), 3) Moving the driver forward in the kart, and 4) moving any added-on weight forward on the kart.

Left Side Weight. Left side weight is much more important to dirt racers. If you have too much left side weight, it makes it difficult for dirt karts to get the right side wheels to work in a corner.

It is very difficult to have too much left side weight on pavement. Some karts run up to 60% . But remember, left side weight may change your cross weight.
Pavement racers take heart. It’s hard to have too much left side weight, but too little left side weight will cause the kart to “bicycle”. Bicycling is when the kart tips up on the right side wheels.

On dirt, too much left side weight makes it harder for your right side tires to get traction. This will feel as if the kart is both loose and pushing at the same time.

Cross Weight. Cross weight controls how the kart transfers weight in the corners. Increasing cross weight tightens up the kart. That means the kart has more forward traction. The kart also has less turning traction.

Decreasing cross weight loosens up the kart consequently the kart will have less forward traction and more turning traction.

How do you change the cross weight? Remember cross weight is Right Front + Left Rear = 100%. So to increase cross weight , you would add weight to the right front or remove weight from the left front. NASCAR guys call this “wedge”. You can move the left rear tire out on the axle, which increases the weight on that wheel.

To recap: To increase cross weight, add weight to the right front or left rear. To decrease cross weight, remove weight from the from the right front or left rear.

This adjustment can also be made by moving the front spindles up or down or moving the rear tires in or out on the axle.

Other Possible Adjustments -

Stagger. Stagger is difference between the diameter of the inside tire and the outside tire. The rear axle in a race kart is fixed so both wheels turn at the same speed. Stagger helps the inside wheel not turn (as quickly) going around a corner.

Changing the width of the wheel that a tire is mounted on, can change the diameter of the tire. A wider wheel will give you a smaller diameter tire. The diameter of a tire changes the base of the air pressure in it. If you increase air pressure, the diameter increases.

Increase stagger loosens the kart up while decreased stagger tightens (removes push) from the kart.

Keep in mind that tracks with long sweeping corners require less stagger than tracks with short tight corners.

Camber. Camber is the degree to which the front wheels lean toward or away from each other. If the tops of the tire are closer together than the bottom, the camber is negative. The opposite is positive camber. To maximize grip when cornering, it is desirable to have as much of the outside tire rubber on the track as possible. Camber is the setting particularly for maintaining maximum rubber on the track in the corners.

Camber is adjusted using the camber adjusters at the stub axle mounting. Many karts have adjustment pins to change the angle of the kingpin. Not all karts have adjustable camber, but it is not usually difficult to fit adjusters if you need them. Karts have very little body roll therefore they need very little camber.

Toe-in and toe-out. This is the degree to which the front wheels point toward or away from each other. Front wheels pointing toward each other is toe-in while wheels pointing away is toe-out. Toe-in makes a kart track in a straight line better, but can contribute to poor turn-in to corners. Toe-out can cause the kart to wander, but can assist the kart turn-in to corners. With toe-out, the inside front wheel move down in relation to the chassis more than it will with zero toe-out or toe-in. Toe is adjusted by lengthening or shortening the tie rods.

Two common oval racing terms that will help you.

Push or Understeer. Push or Understeer is when you turn the steering wheel and the kart wants to go straight. This is caused because the front tires do not have enough traction and they are slipping on the surface of the track.

Loose or Oversteer. Loose or Oversteer is the opposite of push. The rear tires want to swing out around the kart, even though you only turned the steering wheel a little. This condition is caused because the rear tires do not have enough traction. This makes the kart hard to control and you could easily just spin around. If the kart is controllable, a loose kart can be very fast.

Karts can be loose going in to or coming out of a corner. As a general rule, if a kart has trouble entering the corner you need to adjust the front end, but if you have trouble exiting a corner, you need to adjust the rear end.

There are two basic rules to remember that will help you become fast.
A. Adjustments to the front end effects how it enters a corner
B. Adjustments to the rear of the kart effects how it exits a corner

It’s time to go to the track.
1. Learn what adjustment changes the way your kart works.
2. Practice - know what changes in track conditions require what setup changes.
3. Practice making adjustments to the kart
4. Don’t be afraid to ask questions

Suggested Track Adjustments

Problem: Loose into corners

Possible remedies or solutions:
Make changes to front of kart
a. Increase cross weight
b. Decrease caster
c. Decrease front weight
d. Stiffen the front torsion bar
e. Use a softer compound rear tire
f. Widen the front track
g. Use a harder compound front tire

Problem: Loose out of corners

Possible remedies or solutions:
Make changes to rear of kart
a. Increase cross weight
b. Reduce stagger in the rear tires
c. Stiffen rear torsion bar
d. Increase rear weight
e. Decrease stagger in right rear tire
f. Add air to left rear tire
g. Use a softer compound rear tire

Problem: Pushes into corners

Possible remedies or solutions
Make changes to front of kart
a. Decrease cross weight
b. Move right front wheel out
c. Soften front torsion bar
d. Increase front weight
e. Increase rear brake bias
f. Use a softer tire compound front tire
g. Narrow the front track

Problem: Pushes out of corners

Possible remedies or solutions
Make changes to rear of kart
a. Decrease cross weight
b. Move left rear wheel out
c. Increase rear stagger
d. Increase rear torsion bar
e. Decrease rear weight
f. Increase air pressure in rear tires
g. Increase stagger of rear tires
h. widen the rear track
i. use a harder compound rear tires

And finally… Record Keeping
Keep good records of how the changes you make effect the kart. You will not be able to remember what changes you made and what the effect was. Your kart will be effected differently than everyone else’s, even if it is the same brand and model. What takes a ½ inch adjustment for you may take someone else a ¼ inch or 1 inch. You can keep records with a simple notebook or on a laptop with one of the new kart racing computer programs. If you do not keep records of what changes do to your lap times, all you will ever be doing is guessing. A few minutes in the pits may give you the extra edge on the track.

END

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