Dirt Racing TechnologyEverything from basics to the hottest trends in dirt racing today to help win races

Success

What Does it Take to Be successful? Dig to the core understanding of your car. Understand the track your running at. Holding It All Together. Work hard, dont give up, dont stop learning.

Digging into the core of your car Dont get hung up on numbers. Dig everything down to the basics. Dont fall into the trap of the Set up Dont just copy what everyone else is doing; understand what their doing.

Understanding the Track Your Running AtWhat is the shape of your track. Is it a large radius or short radius. Is the track usually slick or is it tacky. How does racing usually shape up. (is it up on the cushion; is it around the hub) What are the driving styles. (fast corner entry; drag racing; early apex; cutting the apex; drifting the straight)

Holding It TogetherGood maintenance! Taking care of the car. Managing Your Tires. All Team members Taking Care of Each Other. Keeping Team Spirit High. Keep Focused at What is Important.

Work EthicSpend Time Working at New Ideas. Keep Working to Improve Reading Books, Magazines, Online Blogs like WWW.Hogantechnologies.com. Keep Pushing Until You Reach Your Goal.

Tires and Traction

What Creates TractionProper Loading of Each Tire at the Appropriate Time. Stretching the Tire to reach its Maximum Traction. Matching the Right Rubber Compound to Track Conditions. Getting the Tire Into the Correct Operating Heat Range.

Traction CircleTo keep tire at Maximum Traction, You need to trade Acceleration and steer Acceleration Amount of Acceleration Maximum Traction of Tire

Left Turn

0 0 Under Utilized Traction

Right Turn

Tire Breaking Loose

Amount of Steer Angle

Braking

Tire Slip AngleThe actual direction traveled will be a derivative of the two. As the tire is turned, the center of the contact patch is twisted.

The slip angle is the difference between the steered path and the actual path of the tire.

Lateral Force and Slip AngleLateral Force Produced by Tire 2500 2000 1500 1000 500 Elastic or tire Stretch Tire stops stretching totally relies on frictional traction Transition Tire reaches its stretch limit and gets into the frictional area Edge of traction

circle

2

4

6

8

10

12

Slip angle in Degrees

Longitudinal AccelerationDesired vehicle direction

Contact patch area is stretched

At point that contact patch releases from surface, it snaps back into position and propels car forward

Contact Patch location

Longitudinal Force and Slip Ratio1500 1250 Tractive Force 1000 750 500 250 Edge of traction circle

.05

.10

.15

.20

.25

.30

Slip Ratio (%)

Tire Grooving and Siping

On tire rule tires, cutting tires into a small pattern will help build heat in tires. Small #1 blade cuts will allow the tire to feel softer and grab the asperities in the track surface. Larger grooves will allow more air to circulate around the blocks and keep them cool. Larger grooves will also dig into the track more than small grooves. Sipes will help build heat into a tire by creating friction within the blocks. Back Cutting Late Model Front Tires Keeps Them Clean and Can add Traction.

Tires Mounting and Preparation Always mount tires with serial number toward the infield Dont use excessive moisture when mounting tires Always keep tires clean between use Be sure to use enough air to push tire over safety bead and seat tire Size and organize tires before going to track If possible use nitrogen or a dry air system in tires.

Tire Grinding Grinding takes the top calloused surface off the tire. Grinding will even the surface and take the top grained surface off the tire. Grinding will take the mold release off the surface of a new tire. Atmosphere and sunlight will start to harden the surface of a tire. Grind your tires as close to the time you are going to run them as possible. Use anywhere between 60 and 120 grit sandpaper on a slow moving grinder to buff the surface. Use aluminum disks where tire rules prohibit siping.

Front Suspension

Understanding and Adjustment

CasterKing Pin Angle Positive Caster Upper Ball Joint

Lower Ball Joint

Front

Caster Caster effect creates a neutralizing or centering effect to the steering. Caster creates a caster wedging when tires are turned. Too little caster car becomes darty and inconsistent. Too much caster makes the car sluggish and difficult to turn from center.

CamberCamber No Camber

CamberCamber No Camber

Camber Thrust

Camber Camber can add side bite to a tire. Excessive camber can cause an un equal loading to the tire contact patch. Lack of footprint. Excessive camber will make the inside tire run too hot. Too little camber will not load the inside of the tire enough and take away side bite.

Camber Gain

Roll angle is 0 degrees

Camber GainBody roll will take camber out so gain needs to be added to compensate

Roll angle 5 degrees

Stagger Camber1 to 2 degrees camber

Left Rear

Right Rear

Stagger Torque The smaller tire will travel a smaller distance for each revolution than the larger radius tire. There will be a backward pulling torque on the smaller tire. There will be a forward pushing torque on the larger tire.

Advantages of StaggerIt will help the car turn a larger radius corner by steering the axle. Will add additional camber, and then will add side bite.

Disadvantages of StaggerStagger torque will have to scrub one of the tires when traveling in a straight line. If left rear is at maximum traction, the right rear will be past its optimum traction for the given tires slip ratio.

Anti-DiveBrake torque holds the chassis up Upper and lower control arm pivots

Front of car Side view

Pro-DiveUpper and lower control arm pivots Brake torque pushes down on the front of the car

Front of car Side view

Anti-Dive Tuning Pro-dive in right front and anti dive in left front helps car squat on right front under braking and helps car turn. Adding or removing shims on lower control arm strut mount. Slotted upper control arm mounts for cars that cant adjust lowers. A small amount of anti-dive can provide a little stability.

ToeFront of car

Toe out = front of tires wider than rear Excessive toe can compensate for reverse Ackerman Toe in = front of tire narrower than rear

Bump Steer Bump steer should be kept to a minimum, but a little used strategically can be beneficial. Some use bump out on the right front to add some stability to car under dive and roll. Some use bump out on left front to add slip angle as car rolls over and starts left turn into corner. Bump steer should be set to at least bump out, if not to zero. Concentrate on right front under compression and left front under drop. Reasonable parameters: .010 in three inches, pretty close to zero for a dirt car; .050 in three inches if you plan on bumping a corner out to tune. The type of track and competition determines precision in bump steer.

Bump Steer Correct

The tie rod needs to move in the same arc as spindle and especially the lower control arm.

Bump Steer / Steer Arm Too Short

The tie rod will move in a tighter arc and pull the spindle towards toe in under bump and rebound

Bump Steer / Tie Rod Too Long

If the tie rod is too long spindle will toe out under bump and rebound.

Bump Steer / Tie Rod Too High on Inner Pick Up

If the tie rod is too high on the rack side, the spindle will toe out under bump and toe in under drop.

Bump Steer / Tie Rod Too High on Spindle Side

If tie rod is too high on spindle side, spindle will toe in under bump and toe out under drop.

Roll CenterWhat is actually going on in the front end, my take on the subject. Do we really know where the front roll center really is? The importance of instance centers and corner jacking. Ideas on kinematic torque on spindles.

Typical Dirt Stock Car Front End ModelUpper ball joint Upper control arm inner pivot

Lower ball joint Right Front Tire Lower control arm inner pivot

Roll Center / Instant CentersLeft instant center Right instant center

Right front tire

Roll CenterLeft instant center Right instant center

Right front tire Kinematic Roll Center

Roll Center Movement

Right Front Tire Roll center moved right under dive and roll

Force Application Point (FAP)Left instant center Center of Gravity (CG) Right instant center

Right front tire Force application points FAP Kinematic Roll Center

AckermanPositive Ackerman is the inside tire turning at a larger degree angle than the outside tire; creating more toe out as turning angle is increased.

A>B

A

B

AckermanNegative Ackerman is the inside tire turning at a smaller degree angle than the outside tire; creating toe in as turning angle is increased.

ABAWeightBWeight TransferThere is two basic kinds of weight transfer.1. Kinematic Weight Transfer: weight transfer through suspension linkages (Fast) 2. Elastic Weight Transfer: weight transfer through springs (slow)Three Axis's of Rotation1. X axis: Longitudinal axis (front to rear) 2. Y axis: Lateral axis (side to side) 3. Z axis: Vertical axis (up and down)Polar MomentRotation Around the Z axisPolar Moment Rotation Axis 200 Lbs 200 LbsSlow reacting, Sluggish Harder to Start Rotation Harder to Stop RotationPolar MomentRotation Around the Z axisPolar Moment Rotation Axis 400 LbsFast Reacting Easier to Start Rotation Easier to Stop RotationLateral Weight TransferRotation around the Y axis200LbsSlow reacting, Sluggish Harder to Start Rotation Harder to Stop Rotation More weight transferRoll Axis, Roll CenterLateral Weight TransferRotation around the Y axisFast reacting Harder to Start Rotation Harder to Stop Rotation Less Total Transfer 200 LbsRoll Axis, Roll CenterLongitudinal Weight TransferRotation around the X axis200 Lbs Pitch CenterSlow reacting, sluggish, Harder to start, harder to stop, more transferLongitudinal Weight TransferRotation around the X axisPitch Center200 LbsFast Reacting, Easier to start, Easier to Stop, Less transferAnti-Squat Adding more angle to the third (torque control) link makes traction happens sooner and run out sooner. Taking more angle out will have less instantaneous traction, but will pull further down the straight.Anti Squat Moving third (torque control) link towards either side will load that side more and sooner. The draw back of high amounts of anti squat is wheel hop under deceleration. The original torque arm devises were mounted right of center to counter balance rear end torque.Best Aerodynamic AttitudeChassis YawChassis yaw will add down force as well as tighten car.Aerodynamic forceForce of the rear end pushing to outside keeps tire stretched to keep side bite in tire as car arcs the straight.Body ShiftHaving front of body outside of the rear pulls air out from under the carAerodynamic force adds down force and tightens car even when pointed straight