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Calculating Spring Rate for QA1 Stock Mount Coil-Over Systems

Choosing a spring rate for a QA1 stock mount coil-over system (also called Pro Coils or direct-fit coil-overs) is easy! This cataloged coil-over kit for your vehicle has already gone through the R&D process and the spring length has been determined, so choosing a spring rate is simply a matter of matching the vehicle weight to our available spring rate charts below. One step softer or firmer than the recommended street spring rate can be considered, depending on the purpose of the car (softer for drag racing, firmer for autocross, etc.).

The first thing needed to choose any spring rate is to determine the weight of the vehicle.

Need to determine spring rates for custom mount shocks? See our Spring Rate Chart & Vehicle Weight Sheet.

Determining Vehicle Weight Without Your Own Scales

How can the home enthusiast figure out the weight of their vehicle? Not everyone has a set of scales in the garage. Weighing your vehicle without your own scales can include taking it to the truck stop, gardening center, or waste collection site, where scales can be driven on.

If scaling your car isn’t an option, QA1 has average vehicle weight charts that can be used to determine the weight of your vehicle. We also offer average weights of different modifications such as big block swaps, air conditioning, or power steering. It is important to add or subtract your modifications when using the average vehicle weight chart.  

For a larger version, see our Spring Rate Chart & Vehicle Weight Sheet.

Determining Spring Rates for Front Shocks

QA1 stock mount coil-overs are a great option for anyone looking for fully adjustable ride height and valving control. Spring lengths have been determined by the application, so you just have to choose the rate. While we provide many options, determining your vehicle weight can direct you to the right one.

Once your front end weight has been calculated, simply choose the suggested spring rate.

For a larger version, see our Spring Rate Chart & Vehicle Weight Sheet.

Determining Spring Rates for Rear Shocks

QA1 also offers cataloged bolt-in rear coil-over kits for popular applications. The spring lengths are pre-determined for each application and we offer these rear kits with soft, medium, and firm spring rates. Most average streetcars will use the medium spring rate, while most drag cars will use the soft spring rate. The firm spring rate would be used for an autocross/road racing application or for a streetcar that say, has a 300lbs. of stereo in the trunk.

Simply choose the suggested spring rate for your vehicle.

For a larger version, see our Spring Rate Chart & Vehicle Weight Sheet.

What if I have a Mustang II front end under my….

QA1 also offers a bolt-in front coil-over for your street rod applications. These coil-overs have been engineered for the Mustang II front end, so matching the vehicle's front end weight to the recommended spring rate is all that’s needed.

Front End Weight:   <1350 LBS.   1350-1525 LBS.   1526-1700 LBS.   1701+ LBS.
Rec. Spring Rate:           375                 500                      600                        700

Time to upgrade your suspension! Please check out the YouTube video for more information.

If you have any questions, please feel free to give us a ring at (952) 985-5675 or shoot us an email.

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