The best place to start any fine-tuning process is literally “by the seat of your pants”. Drivers have different styles and preferences so the set-up that your buddy likes may feel terrible to you. If the car feels uncomfortable to you, then it will probably not be the fastest set-up. You should begin by experimenting with different shock and spring combinations until you find a good overall baseline set-up that works for the widest range of conditions. Once you have a good overall baseline set-up, then you can adjust for different track conditions.
In order to make the correct adjustments, you first need to consider the function of a race car’s springs. The springs are there to insulate the chassis from forces applied through the wheel by irregularities in the track surface. A spring that is too stiff can allow the chassis to accept too much of the force, as too much rate typically causes the car to “skate up” the track with little “sidebite”. Springs that are too soft cause the chassis to use up too much of the suspension travel. Once you have narrowed your spring selection to a good baseline set-up, you can then start realizing the most important tuning function of springs on a race car. When the correct range of spring rate is established, the spring can then begin its job of assisting in the control of weight transfer. The spring determines how much weight is received at each wheel during cornering, breaking, or accelerating. It is at this point that the driver’s “feel” starts coming into the equation. You can now adjust the spring rates to loosen or tighten the car as needed to arrive at the set-up that feels best to you and achieves the results you are looking for – whether it be loose, tight or neutral. When you have arrived at the proper baseline spring set-up, you should then try to fine-tune the handling at the track with shocks and adjustments rather than spring changes. It is best to change springs at the track only as a last resort, but sometimes it has to be done in a situation such as traveling to a high-banked track when your baseline was set for a semi-banked track. In that case, you may need to change to a stiffer spring rate to compensate for the increased loading in the turns. If you are in this situation, pay close attention to your wheel travel making sure that the travel is in the same range as your baseline set-up. The travel can be checked with the travel indicator ring on the shock rod and then compared with the records from testing sessions on your baseline set-up.
When checking shock travel, always be careful to avoid bumps on the way into the pits that could give false readings. Also, be certain that your ride height is the same as before. Find level ground and measure the distance between the shock bearings then, once the new spring is on, adjust the spring to yield the exact same measurement. A quicker way to measure the ride height is to make check gauges when you have the correct ride height set. A piece of small diameter tubing can be used to make the gauges in the shop. With the car on a level floor, cut the tubing to fit exactly in the space between the lower control arm and the bottom of the chassis. The rear gauges can be made to fit between the top of the differential housing and the bottom of the chassis. Label the gauges according to the respective corners they have been cut for to ensure accuracy. The gauges can then be taken to the racetrack in case you need to make a spring change. Remember to always use them in the exact same spot on the chassis.
Now let’s move on to the shock’s role in chassis tuning. One of the functions of the shock is to control the kinetic energy stored in the spring as the spring compresses and rebounds. That is a very simple statement but it is, in fact, one of the shock’s functions. The other, and most important shock function in a race car, is controlling when weight is transferred while turning, braking, or accelerating. The different valvings offered in a racing shock allow you to speed up or slow down weight transfer depending on what the car needs. Fine-tuning can be done by using a different straight valve shock on one or more corners or by using split valve shocks. An example of a straight valve shock is QA1 part #5074, which is a 7” shock with 4 valving in compression and 4 valving in rebound. An example of a split valve shock is QA1 part #5074-6, which is a 7” shock with 4 valving in compression and 6 valving in rebound. This is typically called a “tie-down shock,” since the heavier rebound valving will keep weight at that corner longer. A QA1 part #5076-2 is an example of an “easy-up shock” with 6 valving in compression and 2 valving in rebound. The “easy-up shock” is used to transfer weight off of that corner of the car quicker. The split valve shocks are offered with several different valving options. A huge benefit of the QA1 shocks is that you can custom valve your shocks if you need a valving that is not offered in an off-the-shelf configuration.
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