QA1 Shock Comparison: Which To Choose – Single vs. Double Adjustable

When it comes to performance, most people want the best performance they can get for their money. But sometimes going to the most expensive part a company offers doesn’t always mean you’ve made the best choice.


Single- and double-adjustable shocks can be used with or without coilovers, but to use coilover shocks the car must be modified.

The biggest and the best has its place, but anything in excess might be too much, especially with performance parts that are designed with specific goals in mind. Installing a part that costs the most doesn’t mean it’s going to perform well for you, it must fit the application and performance level of your vehicle.

It is entirely possible to spend too much money for a part if you’re never going to get full use of it. Performance parts have their place, and sometimes a part works best when you get what you need for your car, instead of buying what you want.

Likewise, double-adjustable shock absorbers on a street driven car might not be necessary. For vehicles that aren’t competing at the performance level that double-adjustable shocks were designed for, some may not take full advantage of the adjustment range. Therefore, in many cases a single-adjustable shock absorber might be the best bet for a car that spends most of its time on the street.

QA1 manufactures all of their own parts and assembles their own shocks in house.

Replacement Shock Absorbers

QA1 manufactures shock absorbers for both street and competition, and in many different styles to choose from: stock or custom mounts, single- or double-adjustable, and standard or coilover designs. They design and build all of their drag and street aluminum shock absorbers in-house, and every shock absorber is individually tested before it’s shipped out.

The advantage of manufacturing and building our shocks in-house is that if there are any adjustments that need to be made to our equipment, we can control that ourselves. -Dave Kass

QA1 Customer Service Manager David Kass said, “The advantage of manufacturing and building our shocks in-house is that if there are any adjustments that need to be made to our equipment, we can control that ourselves.”

For a person seeking a standard replacement shock, without the advantage of being able to adjust them, the monotube shocks will provide a comfortable ride and great support for a daily driven vehicle. Monotube shocks are often referred to as gas shocks, and you can tell a gas shock by the way it pushes the rod out, or expands the shock absorber. The high-pressure gas is at the bottom of the shock, with a floating disc that pushes upwards on the shaft, and the oil in the shock is dispersed inside the tube.

A twin-tube shock absorber doesn’t have a gas charge which can add a high level of rod force, it relies on oil pressure and can be identified by its properties. When the twin-tube shock absorber is compressed, it will stay compressed, and when it’s expanded it will remain expanded. Twin-tube shocks have more travel inside the main tube, and the low pressure gas is between the inner and outer tubes. These shock absorbers use oil valving that transfers the oil between the compression and rebound tubes inside the shock body so that the shock can contract and expand with the movement of the suspension.

Ariel Atom2

The twin-tube shock works with low gas pressure, and as the name implies there are two tubes, outer and inner.

A monotube shock can be firm or soft, but they typically expand and work against the springs in a suspension. Sometimes the ride height can actually increase slightly because the pressure in the shock absorber works with the vehicle’s spring rate to expand the shock slightly.

Adjustable twin-tube shocks, however, allow the driver to improve the handling capabilities of their car by making small adjustments to the valving of the shock absorber with a simple click of a knob.

Kass said, “The twin-tube design doesn’t fight the suspension, it allows the spring to perform as it was designed. Adjustable shocks can be for street performance, competition, or even for vehicles that carry a load.”

For our comparison, we looked at the single- and double-adjustable shocks to help decide which adjustable shock design is best for specific applications. Choosing the right shock is more than finding what fits – it’s about finding what works best whether the car is on the street, on a road course, or at the dragstrip.

Every shock absorber is tested in-house at QA1, if it doesn't pass their validation, it's taken apart and the shock is completely rebuilt, not fixed.

Coilover shocks can allow you to set ride height and corner weights. Great for handling, and definitely a cool look on a classic musclecar.

Upgrading To Adjustable Shocks

Coil-over shocks allow for ride height adjustments, for a lowered stance, or an “in the weeds” look. Coil-over systems are available in both a stock mount configuration for many makes and models, along with an assortment of custom mount applications accommodating a wide range of vehicle applications.


We installed the single-adjustable shock absorbers because the car spends most of it’s time on the street.

When it came time to upgrade the suspension on one of our project cars, we installed QA1’s single adjustable shocks because, in addition to it’s duties as a regular driver, we also road race the car on occasion.

We wanted to be able to tune our suspension a little further when we race. Since we only race the car a few times per year, that plays into which type of shock absorber we chose. The single adjustable shocks give us the flexibility to quickly adjust from the setting we like while on the street to the setting that works well at the track.

We upgraded the suspension with QA1’s new tubular upper and lower control arms; a direct replacement of the factory components with an additional three degrees of caster built into the arms. Adjustments to the camber and caster can be made to change the way the car handles on the street – and how it performs at the track. We installed adjustable shocks for that very reason – because we wanted to be able to make adjustments when we race, and easily return to our street settings.

The single-adjustable shocks work great for the occasional track visit, and allow a more performance oriented set up for the street while maintaining a comfortable ride.

Racing and Shock Absorbers

For drag racing, you can adjust your shocks to give you better launches and to control a wheelie. Setting a softer compression in the rear will help keep the car planted under heavy acceleration, giving you more traction. A firmer rebound in the rear will keep that launch more stable and keep the rear from lifting too quickly, which affects traction.


Adjustable shocks in drag racing help control the wheelie and helps with weight transfer to the rear tires.

Adjusting the compression and rebound of the front shock helps control the launch. A softer rebound allows the front to lift easier, which helps tremendously with weight transfer to the rear tires. A stiffer compression will help keep the front end more stable when it returns to earth.

A single-adjustable shock absorber for occasional quarter mile passes will work, and allows you to make the adjustments back to street driving on the trip home. But Kass said, “Independent control of the compression and rebound on double-adjustable shock absorbers are beneficial in higher levels of racing programs.” You simply can’t get the same type of control with a single-adjustable shock if you’re racing competitively.

Unless you’re a hardcore racer who is going to race in a competitive environment, you might not see the true benefits of the double-adjustable shocks. -Damien Brase

We talked with Damian Brase, Technical Sales and Support at QA1, about how to choose between single- and double-adjustable shocks. Brase said, “Unless you’re a hardcore racer who is going to race in a competitive environment, you might not see the true benefits of the double adjustable shocks.” It’s good advice, because if you’re only racing a couple times a year, points and standings probably don’t weigh in as much as they would for someone who competes monthly.

The settings for drag racing are primarily made based on launching the car, and affect how it handles in a straight line. If the car doesn’t feel right at launch, a simple click of the knobs can help improve your 60-foot times. Dialing the shocks in is not terribly difficult, and you can generally find the sweet spot in just few passes. Once that is done you can focus more on the race.

For road racing and autocross, the adjustments are based on different parameters than with drag racing. With drag racing, the go-stick is pressed and the weight needs to be transferred to the rear for traction. For road racing, weight transfer can happen in just about any direction, so the adjustments need to be made with different goals in mind.

Making adjustments to a single-adjustable shock is a simple click in either direction, and back out on the track to see if there is an improvement. While the double-adjustable works in the same fashion, it will take more time since there are two knobs to adjust. You can find the right compression setting, but the right rebound setting might take a few more laps before you dial it in.


We like to drive this car fast…and turn. So QA1’s adjustable shocks help us dial in our handling a little better when we need it.

Once you find the right setting, it’s best to record it somewhere for the next time you’re at the track. Stiffer settings can cause a very uncomfortable ride on the street, where potholes and uneven pavement are the norm. If your car sees double-duty, you’re probably not going to like the firm settings for street driving.

Whatever your setting is for one track may not be the best setting for the next track you go to. With 18 settings for each knob on a double-adjustable shock, the tenability is at your fingertips, and that’s why Brase recommends that the double-adjustable are better suited to those who compete regularly.

Those who race often prefer double-adjustable shocks because they spend more time at the tracks and the double-adjustables allow them to fine tune their suspension and make the best possible handling vehicle. It’s paramount to have the best set up and to spend that time finding what works best because a well tuned suspension can shave a few seconds off of lap times.


Adjusting the shocks can help control the wheelie – and improve your 60-foot times.

Competitive racing usually means more than one track, and that means adjusting the shocks for various tracks or autocrosses. After setting up adjustable shocks for one track, the settings are often recorded and then the process is repeated for other tracks that might have different elevation changes or off-camber turns. Changing tire compounds or sizes can also affect those settings, and that means more changes are necessary to get the most of your shocks.

If you’re installing some power adders, or bigger brakes, you’ll likely be changing your shock settings again because power and braking changes can also affect the way your car handles. As you can guess, with adjustable shocks anytime you make changes to your car with regards to power, weight, or handling, you will most definitely need to adjust your shocks if you want them to perform at their best. Without these adjustments, your shocks could be working against you – not for you.

Adjusting  Single- and Double-Adjustable Shocks

Usually when you get an alignment on your car, you can make small adjustments to the camber and caster that will improve handling on the street, or make bigger adjustments that can give you the best grip at the track. However, bigger camber adjustments to improve handling at the track can promote unwanted tire wear on the street. It’s not unusual for a competitive racer to go through a set of tires during a weekend of racing because they’re pushing their cars to their limits and the suspension is adjusted to provide the best handling. Street set ups are for the least amount of tire wear and for a comfortable ride.

Oversteer vs. Understeer

Understeer is when the front tires push into a turn instead of following the curve, your car is not turning as much as it should – hence “understeer”.

Oversteer is when your front tires grip more than the rear, and the rear begins to slide around in the turn, your car is turning more than it should – hence “oversteer”.

QA1’s single-adjustable shocks are available in a few different styles suiting different driving needs. One allows you to make adjustments to the compression and rebound properties of the shock absorber with one adjustment knob. They have 18 adjustments from soft to firm, all by turning the adjustment knob one click at a time with a positive detent for each setting. QA1 also offers a rebound only adjustable shock for ride comfort focused builds, and also a drag race “R” series valving.

The double-adjustable shocks allow you to make separate adjustments to the compression and rebound properties of the shock absorber with two adjustment knobs. Each knob has 18 adjustments that work independently of each other, to help dial in the handling even more.

Fine tuning the front shocks to be a little stiffer or softer than the rear shocks can help you dial in the amount of oversteer or understeer that you get when cornering. QA1 recommends that your rear shock absorbers are set slightly softer than the front by a couple of clicks to start with, and that you adjust from there.

But how can shock stiffness create oversteer or understeer, you ask? Stiffening a front shock absorber helps control the body roll, which in turn gives the front tires a better grip on the pavement. Think of stiffer shocks as temporarily stiffening up your springs when you need it the most; we know that stiffer springs will allow a car to handle better, and the advantage of an adjustable shock is that one can adjust the shock to provide a little more stiffness to the suspension.

Body roll affects the way the tires grip the pavement, and when there is too much body roll at either end, that end becomes looser in the turns than the opposite end of the car. This is why you should adjust your suspension at both ends to dial in the proper handling.

When cornering, a softer compression and rebound setting on the front shocks will allow more body roll because it allows more weight transfer from side to side. As one side of the car compresses from the softer settings, the other side extends. Stiffening the front shocks will help decrease body roll, and that helps maintain good contact with the pavement from both front tires.


A standard, steel gas shock is also a lot heavier than the adjustable twin-tube shocks from QA1 with their aluminum construction.

Adjusting the front shocks too firm on the compression side can cause understeer. By keeping a firm setting in the front, and adjusting the rear stiffness, you can actually dial oversteer in or out. Sometimes this takes a few times around the track before you find the perfect balance.

The rebound setting adjusts how quickly or slowly the shock absorber will extend after being compressed. Setting it stiffer will slow down the time it takes to rebound, setting it softer will allow the shock absorber to extend quicker.

How much can these minor adjustments improve lap times? We had our car out on the autocross and turned in a decent lap time, but the car wasn’t handling as we were used to. A few turns of the knob on each shock absorber and we were able to reduce our lap times by about four seconds, on average.


QA1 shocks are rebuildable, oil in the shock housing is transferred through small passages in the piston.

For handling,QA1 recommends a baseline that both knobs on double-adjustable shocks be set between 4-6 on compression, and 10-12 clicks on rebound, and that adjustments are made from there by taking the car out on the track and making adjustments to improve the handling. For single-adjustable shocks they suggest starting with 4-6 clicks, and making adjustments after driving.

The bottom line is that nobody can tell you point-blank what your settings should be for your adjustable shocks. The only real way to tell is to start at a midpoint, drive the car, make an adjustment and drive it again. As we said, it may take a few passes, but once you figure it out your handling will improve – and so will your lap times.

For more information about QA1’s adjustable shocks, check out their website and don’t be afraid to call and ask for some assistance with setting up your shocks. They know each car is different, and people have various driving styles, and they have the right people in place to help you set up your car best for the way you’re driving it. They can give you a baseline setting – and they can tell you what to look for to further fine tune your suspension.

Article Sources

About the author

Michael Harding

Michael is a Power Automedia contributor and automotive enthusiast who doesn’t discriminate. Although Mopar is in his blood, he loves any car that looks great and drives even faster.
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