Old 05-27-2008, 09:52 AM
  #63  
rcbarrmeister
Tech Apprentice
 
Join Date: Dec 2004
Posts: 88
Default Chassis tuning info

Below are a bunch of good tips and info I found, taken directly from the Customworks Aggressor Manual. Note that some examples are specific to the Customworks car and may not apply to all pan cars as they may not have the same adjusting capabilities. However the theories should still apply. Enjoy!

TUNING TIPS: These are some general guidelines for optimizing handling
performance. None of these “tips” are EVER set in stone. On any given day this manual or any chassis engineering book or guru can be proved wrong by the almighty stop watch. A good way to approach chassis set-up is to try one change, practice it, think how the car felt different from before, and compare lap times from the stop watch…..this will never fail.

Car is Loose or Oversteers
Install Wing to Rear of Car
Slide Wing Toward Rear of Car
Increase Wing Angle
Add Wedge/Tweak to Chassis Using Side Shocks
Softer Side Shock Springs
Stiffer Front Springs
Softer Center Shock Spring
Decrease Center Shock Spring Tension
Try Harder Front Compound Tire
Try Softer Rear Compound Tire
Move Battery to Center of Car
Raise Front Ride Height
Lower Rear Ride Height
Move RF Suspension Out
Move RR Tire Closer to Pod
Increase Castor

Car Pushes or Understeers
Slide Wing Toward Front of Car
Decrease Wing Angle
Remove Wedge/Tweak to Chassis Using
Side Shocks
Stiffer Side Shock Springs
Softer Front Springs
Stiffer Center Shock Spring
Decrease Center Shock Spring Tension
Try Softer Front Compound Tire
Try Harder Rear Compound Tire
Move Battery Toward Left Side
Lower Front Ride Height
Raise Rear Ride Height
Move RF Suspension IN
Move RR Tire Away From Pod
Decrease Castor

Car is Erratic:
Bent Front Suspension Pin: Remove spring and check for free movement
Chunked Tire: Check side wall to see if rubber is still glued to wheel.
Bent Axle: Tire “wobbles” while spinning.
Loose Screws: Especially Chassis Screws, add Blue Loctite to prevent.
Bound Ball Joint: Steering link and shocks should spin free on balls.
Shocks: Either Bound Up, Bent Shaft, or Out of Oil.
Bearings: Broken or completely seized.
Foreign Objects: Unlucky Dirt/Stones preventing suspension movement especially in front pivot balls.
Bottoming Out: Look on bottom side of chassis for buffed or scratched areas.
Tire Rub: Look on inside of body for extreme black marks from tires.
Blown Differential
Radio Problem: Bad Servo, Weak Servo Saver Spring, Transmitter Pot blown.

Castor: Angle of the kingpin in relation to a vertical plane as viewed from the side of the car. Increasing the angle will make the car more stable out of the turn as well as down the straights and increase steering entering a turn.
Decreasing the angle will make the car feel more “touchy” at high speeds and help steering while exiting the turn.

Front Toe IN: Front edge of car tires point toward the chassis as viewed from above the car. Settles and makes steering reaction less aggressive especially on acceleration. Easier set-up to drive and works well on bumpy tracks.

Front Toe OUT: Front edge of car tires point away from the chassis as viewed from above the car. Increases aggressiveness of car especially on entry to the turn. Works well on smooth, high bite tracks where rear traction is not a problem. Generally the preferred set-up for pan car racing.

Camber: Angle by which the tire and wheel contacts the racing surface when viewed from the Front or Rear of the car. Oval cars generally always have the Right Side tires leaning TOWARD the chassis and the Left Side tires leaning AWAY from the chassis. In oval racing jargon, more camber means more angle TOWARD the chassis on the Right Side and more angle AWAY from the chassis on the Left Side. Starting from 0 Degrees (tire standing
straight up) ADDING camber in the oval fashion will increase traction when cornering however remember too much of anything is generally a bad thing. Camber is usually adjusted (especially foam tires) when one edge of the tire is wearing more than the other.

Camber Gain: Angle of the Upper Suspension Arm relative to the ground, so that when the suspension travels the amount of camber for that tire will increase. With the arm parallel to the ground the front suspension will have the least amount of camber gain. Lowering the Upper Suspension Arm on the Upper Suspension Mount will increase the amount of camber gained when the suspension travels. There is not a “correct” set-up and once again
too much of anything is generally bad. This will help change the “feel” of the car thru the turns.

Shock Angle (Center Shock): Mounting the shock in the lower positions will increase the stiffness of the spring and generally works best on smooth high bite tracks. Mounting the center shock in the upper positions (shock parallel to the ground) will make the spring feel softer and works best on low grip surfaces and bumpy tracks as well.

Shock Angle (Side Shocks): Mounted in the shocks in the lower positions will increase the stiffness of the spring and will decrease chassis roll which is good for high bite tracks and especially flat tracks. Side Shocks mounted in the upper holes (shocks parallel to the ground) will make the springs feel softer and will increase chassis roll which seems to be best for cap tire racing and low bite flat tracks.

Tweak: Refers to the amount of weight placed on the Left Rear and Right Front tires by adjusting the collars on the side shocks. Threading the collars IN on the right side shock and OUT on the left side shock will place more weight on the Left Rear tire and on the Right Front tire and will make the car push. Threading the collars OUT on the right side shock and IN on the left side shock will place more weight on the Right Rear tire and Left Front tire and will make the car loose. Generally the car is always set-up so that it is “tweaked” so that the Left Rear is heavier than the Right Rear. You can check to see how much weight is on each rear tire by using a hobby knife to pick up the rear of the car under the center of the rear pod. The Right Rear should come off the ground about 1/8" inch before the Left Rear does. The higher the Right Rear comes off the ground before the Left Rear does, the more tweak and more weight that is on the Left Rear.

Ride Height: Check by pushing the chassis down once or twice to simulate bumps on the track. Having the front end higher than the front will make the car increase rear traction especially out of the turn. Having the front end lower than the rear end will make the car increase front traction especially entering the turn. Generally a safe place to start is with all corners of the car even with 1/4" ride height under the chassis. Since these cars sit so close to the ground even 1/16" difference is drastic.

Battery Placement: Since the battery is the single heaviest component in the car its placement is critical. Moving the battery further to the left will make the car turn more thru the center of the turn and coming off but will decrease forward bite. Placing the battery closer to the center of the car will work better on low bite tracks and increase forward bite.

Wheelbase: Wheelbase is the distance between the front and rear axles. Mounting the entire front end assembly in the forward position (10 3/8") will make the car more stable on long fast tracks with flowing turns or tracks with low bite compared to the power used.
Running the entire front assembly in the rear most position (9 5/8") will make the car more suitable for short tracks where you are constantly turning. Using the middle position (10") is a happy-medium of both set-ups described.

Long Pod: Unique to this car is the option to increase the length of the rear pod and keep the wheelbase and body mount positions the same. Increasing the pod length (distance from axle to t-bar) makes the center shock and t-plate effectively a lot softer and best for severely bumpy conditions and flat tracks.

Front Track Width: This can be viewed as the distance between the two front tires but more accurately it is the distance from the center of the car to the individual tire. For example moving the Right Front tire closer to the center of the car will increase the amount of weight transferred to the tire when cornering, best used when the car is extremely tight. Moving the Right Front away from the center of the car will decrease the amount of weight transferred to the tire when cornering, best used when the car is
extremely loose or over aggressive to drive. Since the majority of the cars cornering ability is done thru the Right Front tire, moving the location of the Left Front tire will not be near as drastic but will help fine tune your set-up.

Rear Track Width: Distance from the rear pod the tires are mounted. This is accomplished using spacers on the axle located between the bearing and the hubs. Moving the Right Rear away from the pod will increase steering in the center of the turn and exiting while decreasing forward bite off the turn. Moving the Right Rear closer to the pod will increase forward bite thru the center of the turn and especially while exiting. The opposite can be said for the location of the left rear. Mounting the left rear close to the pod will increase steering thru the center of the turn and decrease forward bite off the turn, while mounting it further from the pod will increase stability and forward bite while cornering.

Rear Pod (On-Center or Offset): Mounting the pod “on-center” positions the motor (which is the majority of the weight of the rear pod) pretty much center in the rear pod and generally works best in wide open type driving classes like stock. Mounting the pod “offset” places the motor closer to the left rear tire and helps keep the left rear tire planted during acceleration and works well in modified classes.

T-Plate (On-Center or Offset): Unique to this car is the option to run the t-bar offset from the center-line of the car. Along with offsetting the t-bar the rear shock tower and shocks also offset creating even more left side weight on the chassis. This feature works well for flat tracks and especially modified classes when getting the power to the ground is critical.

Rear Steer: This feature allows you to run the axle straight in the car or angled ½ degree so that the rear helps turn the car in the same fashion as four wheel steering. This option works best on tracks where you are constantly turning and when forward bite off the turn is not a problem.

Rear Wing: To increase traction to the rear of the car wings can be mounted to the rear window of the body for foam tire racing or directly to the rear pod for cap tire racing. Generally every class of pan car racing uses a rear wing, with the exception of stock classes on very high bite tracks since the wing is extra weight and aero drag. On banked tracks the wing is mounted very flat and below the roof of the car so that just the side dams of the wing keep the car stable at high speeds. On flat tracks the wing is mounted at least even with the roof height of the car and angled up almost as much as the angle of the front window of the body.
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