Copy from "Setup Workbench"
The Dreaded Tweak
You will often hear drivers say my car is tweaked around the pits, followed by some colourful adjectives  .
A tweaked car will cause of a car to turn differently left than right or spins under power or braking even when the steering is pointed straight. When the following settings have are un-even on the left side and right side of the car, then you will have a tweaked car.
A twisted chassis
Un-equal shock lengths
Un-even droop settings
Un-even shock collar settings
Un-even swaybar settings
When your car is tweaked you should check each of the above causes in the order they are listed and correct any inconsistencies. If your car is turning differently left than right and it is not because you have more steering throw one way versus the other then it is time to check the tweak of your car.
Twisted Chassis
It is important to start with checking for chassis tweak as every suspension component hangs off of the chassis. Thus the rest of the suspension components will magnify any imperfection in the chassis. To check for chassis tweak you will need to place the chassis on a perfectly flat surface such as a setup board, after you take off the tires and any battery straps. Most working surfaces at your local racetrack will not be flat and since we are looking for a tweak that might be only 1mm a perfectly flat surface is a must. If after you place the chassis (without tires and battery straps) on the flat surface, the chassis rocks back and forth in any direction then the chassis is twisted and thus tweaked.
Assuming the chassis is twisted, how do you fix this? If you have a chassis that is comprised of an upper and lower deck then you can typically fix a twisted chassis. To fix this apply the following steps:
1) Undo the screws on the upper deck, the lower chassis, and the shock towers, a couple of turns, and give the chassis a little twist both ways to un-bind anything that might be bound up.
2) re-tighten the screws on the lower chassis.
3) Place the chassis on a flat surface and re-tighten the screws on he upper deck.
4) re-tighten the shock tower screws.
Un-equal shock lengths (left to right)
Another common cause of a tweaked car is when the shocks are different lengths. We are more concerned about comparing a left shock versus a right shock and not so concerned about comparing a front shock to a rear shock. For example, if the left rear shock is longer than the right rear shock then when the car turns left the car will roll more than when it turns right, which will cause the car the turn differently left than right. To make sure the shocks are the same length, use a measuring device to measure the length of the shock from hole to hole. A 1 mm difference between two shocks is a lot.
Un-even droop Settings (left to right)
If the left and right rear have different droop settings, or the left and right front has different droop settings then your car will not accelerate and brake in a straight line, and it will turn differently left than right.
For example, if you have more droop in the rear left than the rear right then when the car turns left the car will roll more than when it turns right, which will cause the car the turn differently left than right. The left and right droop should be identical.
Un-Even Shock collar settings
If the left and right shock collar settings are not equal then you will typically have one shock that has more tension and thus feels firmer than the other. In addition to causing the ride height of one side of the car to be higher than the other this will cause one side to be firmer than the other. Both of which will cause the car to handle differently when turning left versus turning right.
Note: Even though the theory says the shock collar settings should be identical, things such as minor imperfections in the chassis and slightly different spring lengths will require a very small difference in the shock collar settings.
Un-Even Swaybar settings (left and right)
Please refer to the swaybar section on how to ensure a swaybar has the same setting on the right side as the left side. |
