Drag racing newcomers often fall prey to the ideology that performance and consistency both begin and end with the rear suspension configuration and setup. After all, that’s where the drive tires are, right? In reality, though, the rear suspension works in direct concert with the front shocks and springs, and what’s going on up front can make or break you, whether you’re a heads-up or bracket racer. At the end of the day, it’s all about transferring weight adequately and efficiently, and while it’s not rocket science, there’s much to be learned through trial and error to balance the setup.
With the help of the gang at QA1, we’ll work to take some of that trial and error out of the equation to get you in the ballpark and on your way to quicker, more consistent launches.
Most drag racing and performance suspensions include some shape or size of adjustable shocks as the norm. Mastering the shocks and springs is as definitive as putting the best racing engine together yet missing on the tuneup. With input from Steve Smith, the Lead Technical Writer for QA1 High Performance Suspension and Driveline, we will concentrate on your front suspension and provide some in-depth explanation of shock and spring applications, along with their tuning.
Stored Energy In Your Front Springs Is The Key Starting Point
Before we get into shock tuning, let’s look at the springs that a racer installs on their front suspension.
“Whether it be a stock-style spring, one of our stock mount coilover systems, or a true custom mount coilover shock system, your front springs should be compressed by the weight of the car at 30-35-percent of that spring’s overall length,” Smith explains.
Smith adds, “This spring compression baseline is crucial at placing stored energy in the front suspension movement. This energy is a big factor in extending the front end of your car upward on the launch. It is then that our shock adjustments will control that energy and motion.”
We know, for example, that the QA1 coilover spring mounted in the stock subframe of our Project Rover first-gen Camaro has an uncompressed length of 10.25-inches; with our ride height set and the full weight of the car in place, our compressed length on our spring is 7.25-inches. According to the spring rate technical pages on the QA1 website, our current compression rate for our front springs is 29.5-percent. The lighter spring compression makes sense, as the car has gone under a serious front end weight reduction since purchase.
“The recommended spring rate charts on our website are based on street cars. If you’re setting up a drag race-only front suspension, you can take the spring recommendation from our website and choose a spring that is one spring rate lighter to give you more stored energy,” Smith explains. “For example, if your car is calculated to run a 450-lb. spring, you can use a slightly lighter 400-lb. spring on your drag car to provide more spring compression to aid the launch.”
With that said, our Camaro will be receiving a jump from a pair of 500- to 400-lb. springs, not only to correct our current spring compression of only 29.5-percent but also to achieve extra stored spring energy, since we are using this in a race-only application.
“On the other extreme of things, if you’re using too soft of a spring that allows too much compression, you don’t have adjustable ride height,” Smith continues. “I will hear a customer say that their adjusting collars are jacked all the way up, and the car is still not coming up to ride height. That’s when you know you have too soft of a spring.”
Smith notes, “Adjusting the vehicle to your desired ride height may leave the spring seat collars sitting at any height on the shock threads. Having available compression and rebound travel at ride height is more important than where the collars end up.”
If you scale your front end weight and select one spring rate softer than our street car charts provide, you can verify the compression target after the spring is installed. With 30-35-percent of the spring compressed, there should be no surprise when the spring correctly does its job. – Steve Smith, QA1
Shock Tuning Is A Matter Of Regulating Suspension Movement
Tuning the front shock rebound and compression is a practice of observation first and then making adjustments based on how the car reacts. There is no magic formula for achieving a proper shock adjustment while the car is sitting still.
“Variables such as suspension geometry, overall racecar weight transfer, rear suspension settings, horsepower, and torque, can all be affected by your front shock adjustment,” Smith says.
With the ease of shooting video today, Smith stresses the adjustment of your front shocks by means of using a video camera. This playback will not only let the racer review what the front end of the car is doing, but also will illustrate chassis flexing, side-to-side movement, and how the back tires load or unload in relationship to the front end travel.
“We are concentrating on the front suspension motion to achieve weight transfer to the back of the car to increase traction,” Smith explains.
If you’re starting from scratch with your front shock setup, QA1 recommends adjusting your front shocks to the softer side for maximum weight transfer and tightening as needed after seeing how the car reacts. Smith says, “Our goal is to get maximum weight transfer without huge wheelies at the launch.”
“When your car launches, analyze how quickly and how high the front end comes up,” Smith describes. “If the front end rises just enough to fully extend the suspension and slightly pull the tires from the racing surface, that is your optimum weight transfer.”
At any point in your videos, if you view an abrupt change in the rear suspension movement or on the sidewall “wrinkle” pattern of your slicks, rewind your video and observe what the front suspension is doing at that precise moment.
Rebound Adjustment Basics
If the front end rises too quickly, you can harshly top out your front suspension movement and cause your rear slicks to unload. By carefully watching your runs, especially in slow motion, it is essential to observe the rear tires, as well.
“To achieve proper shock rebound, also called ‘extension’ by various shock manufacturers, you will adjust the rate of motion to get a desired front end rise,” Smith instructs. “If the front end is wheelstanding or rising too quickly, you need to stiffen the shock rebound at the adjusting knob to slow the rate of rise.”
Compression Adjustment Basics
“The goal of adjusting the compression side of your shocks is to create a proper settling of the front end following the launch,” Smith stresses. “If your shock settings are proper, the car will set the front tires down gently and slowly continue to settle down the ride height as the car continues to accelerate down the track.”
As the car continues to accelerate down the track, it should not settle to ride height immediately. You should extend the weight transfer to the rear tires at a lesser rate as the car continues on your pass.
If your front compression settings are too soft, the car will come down to earth too quickly, thus letting the front end bottom-out the front suspension or even cause a bouncing effect following the launch.
Soft compression setting can be a big problem, as it causes the rear suspension to unload as the weight transfer drastically changes from the front end bottoming-out.
“If your front shocks are set with too stiff of a compression adjustment, it will force the tires to strike the racing surface when they come back in contact from a wheelstand, as opposed to gently settling down,” Smith adds. “This creates the same unloading effect on your weight transfer as a soft setting allows your front suspension to bottom out. Many instances of tire-shake or spinning are the effect of your weight transfer jumping around with a poorly adjusted front suspension motion.”
Making The Adjustments
With 18 settings between soft and hard shock valving, the QA1 chart for single-adjustable front shocks advises beginning at 0 to 6 clicks clockwise from the softest or “-” position on your front shock adjusting knob.
The adjustability advantages of a double-adjustable shock are illustrated by QA1’s recommendation to begin with 12 to 16 clicks from the softest setting with the compression valving and 0 to 4 clicks with the rebound.
Many knowledgeable racers will soften or tighten their shocks with a “two-click” method: as you adjust the settings stiffer or softer, adjust in two-click steps — then, fine-tune with single clicks as you get close to an optimum setting.
“If you can’t control your front end travel with these steps, the car may have other problems,” Smith says. “There are some theories about tuning shocks from side-to-side to compensate for torque and steering motion — I contend that if you need any adjustment greater than four-clicks from side to side, you likely have other chassis problems to address.”
Clicks To Win
Whether you’re fine-tuning your front shocks and springs for consistency or all-out performance gains, all these adjustment theories hold true to get the most from your racecar based on the motion of your front suspension.
Smith’s final point seemed best to finish these fundamentals on spring and shock tuning.
“My overall pitch with anything to do with suspension on a drag car is that what works for the guy in the pits next to you doesn’t mean anything to your car. You must get the correct spring and shock setup to begin with, set your base settings, and adjust based on how the car reacts from there.”