Swift Springs USA

Nearly 10 years ago Swift began selling coilover replacement springs in Japan to tuner shops and performance auto retailers. Most of the time these shops were puzzled why anyone would sell “replacement springs” for coilover systems since they all came with springs already. Now Swift springs are regularly sold in shops. Once people saw replacing springs can improve the comfort of the ride, coilovers on the street became more and more popular. Here is a list of normal questions we heard from both shops and end users.

1. My coilovers came with springs. Why do I need to replace them?

Everyone's purpose, driving style, and vehicle weights are different. These factors can change the demands put on the suspension. Most coilover system have a selectable dampening rate that control the shock's ability to compress (bound) and extend (rebound), as well as ride height adjustments.

For example, you have a low ride height stance on your current set up. The vehicle is only used on the race track. You will most likely set your dampening rate as stiff as your traction will allow. The height and dampening setting along with track layout will reduce the necessary stroke you will require.

To prevent your car from bottoming out and damaging the chassis of your vehicle, you will require a heavy spring rate to avoid the compression point where you will hit the bump stop or bind the coil spring. Since you have limited your stroke, you may not require a tall spring either. By shortening an 8" spring by an inch or two, you can reduce the un-sprung mass which can result in improved acceleration (sprung to un-sprung mass characteristics), improved traction during rebound over uneven surfaces, and during heavy cornering.

Also, many of the inexpensive coilover kit have low quality springs. By installing a longer springs and adjusting preload on your coilover system, you can retain more stroke (up to coil bind), and you will also experience a smoother ride for every day street driving.

2. I have a set of coilover on my vehicle, and race at the track occasionally.
I don't want to lower my spring rate, but I want to improve my street driving comfort..

Not to worry, our coilover replacement springs are designed with a super liner characteristic you can change out your springs with the same spring rate and still get a far superior ride quality. Second, by using a lighter weight spring, the transitions from compression to rebound are much quicker, and therefore would enhance the level of ride comfort.

3 What are the factors I should look for when I choose the best springs out on many brands?

When choosing springs that are most suitable for you, you should always look fo
characteristics that the spring manufactures offer.
Make sure that characteristics are what you are looking for.
For example, our coilover springs are engineered with four main emphases.

1 The amount of usable stroke within the selected length.
2 The longevity & durability from sagging
3 The linearity characteristic
4 The light weight and less coil design .

4. I spoke with the coilover manufacturer and they said that I shouldn't use your springs with their system. Why would they say that if you say I should?

Well the truth is that you can use our springs for any type of coilover system. In reality, there is no such thing as a coilover kit that doesn’t need to be changed. Everyone picks the coilover shocks, and then the springs separately. Any coilover manufacturers that offer springs with their coilovers are Swifts competitors. Their business-minded logic says to them “Why tell customers to buy from a competitor.” In a strictly business sense this is completely logical and understandable.

Some brands have chosen to embrace our quality into their brand. Zeal and DG-5 is a great example of a brand secure enough in our quality of products, and that they provide their customers with their high-end coilover systems with Swift springs right out of the box.

5. But the coilover manufacturer said switching springs can damage the valving of my coilover systems is this true?

It depends on the range. If you have a street designed coilover system and add 24kg/mm springs then the answer is No. We too have heard of customers and even racers hearing feedbacks from manufacturer’s statements like: “Shocks are designed for our springs only”,”Swift springs can damage valving because it’s different”. If this was true than they would have to sell separate coilover shocks for every spring rate at the very least.

The most important factor in valving is the durability and quality of the valving design, materials, and manufacturing in the first place. So if a manufacturer tells you it will damage the shock, the next phone call should be to a Motorsports suspension tuner, they will most likely give you most experienced and unbiased opinion.

6. I have spring with a 2.25" 2.5" or 2.75" ID. Do your springs fit?

Yes, they do. Although there is a very small amount of difference, they do work fine.
Please look at the chart below.

60mm – 2.25” 2.25”=57.2mm 60mm=2.36”
(0.1”, 2.8mm difference)

65mm – 2.5” 2.5”=64mm 65mm=2.56”
(0.06”, 1mm difference)

70mm – 2.75” 2.75”=69.9mm 70mm=2.755”
(0.005”, 0.1mm difference)

As you see, there is not much of a difference.

Please start by checking your existing spring's inner diameter.
You will probably notice that they are greater than what they advertise.
This is to avoid too tight of a fitment.

7. What is the difference in progressive and linear springs?

Linear
Well linear spring theoretically keep the same spring rate regardless of stroke.
If you have a 6kg/mm linear spring, if you compress it 10mm it should only take an additional 6kg to compress another mm. Therefore, if you compress a linear 6kg/mm spring with 60kgs of force, it will compress 10mm.

Linear Spring Characteristics
The benefit of a linear spring is consistency, meaning the weights transferring from side to side should be very smooth and consistent. After getting use to the car dynamics, drivers can anticipate weight transfers and body roll more accurately. While exiting a corner, a linear spring will return the body in a smooth manner because both sides are compressing and rebounding at the same rate, which keeps one mm of expansion to one mm of compression throughout the traction of the springs. This reduces the demand for excessive counter steering, which can result in fish tailing. For winding roads driving, this has great benefit and allows for more confident use of weight transferring because the driver won't experience unpredictable weight shifts.

Progressive
Progressive springs are springs that gradually increase spring rate as the spring compresses. So, if the spring starts out with a 6kg/mm spring rate after 50mm of compression it may then measure 17.75kg/mm.
Using the above example a 6kg/mm linear spring will take 300kg to compress 50mm while it will take 594kg to compress the progressive spring.

Progressive Characteristics
Say you are cornering with these progressive springs, you have compressed your outside spring by 50mm (a little over 2"). While you are exiting the corner the centrifugal channeled inertia (the force that causes body roll during cornering), reduces, allowing the body roll to stabilize. You now have an outside spring that has stored 17.75kg/mm of force. As the centrifugal inertia reduces, it throws the outer side of the chassis up with 17.75 kilograms per/mm of force, roughly 950lbs/ inch of force.

Since suspensions are designed to keep the vehicle level that force throwing the outside of the chassis up will be partially transferred to the opposite side. But the outside spring has not compressed during cornering so it will absorb the transferred energy at 6kg/mm of compression so for the first mm the outside releases, will translate to almost 3mm of compression on the inside. As the outside spring releases the excess energy and the inner springs absorb it, the ratios gets closer to 1:1, it may even change back and forth. This is excessive body roll requiring more attention and finesse to effectively control. While negotiating chicanes it can make steering extremely complex and demanding compared to what linear spring would produce. Please use the chart below to see the differences in the linear and progressive spring characteristics. .

8. I have coilover lowering spring kit that is made up of sleeves that fit over any OE shocks will Swift's coilover springs work with it?

Yes. We will need you to measure the springs to make sure you get the correct replacements.

9. How do I measure my springs for replacement?

Using a set of measuring tape, measure the inner diameter of the spring you currently have. Measure the free length of the spring you have and round it to the nearest inch.
Spring rate should be provided by contacting manufacturer of your system.
Many brands also print the spring rate on the physical spring itself. Depending on manufacturer and model, this rate and size may be different..

10. How much can I adjust a spring rate?

Depending on the specification provided by the manufacturers and the different models! For basic guideline, you should not increase or decrease the spring rate more than +/- 4kg (225lbs/inch) from systems stock rate. High end performance oriented coilover system may be able to customize further but you should speak with your manufacture about the tolerance. Otherwise, you may speed up the ware on your shock valving. If you are willing to have your shocks inspected and revalved regularly, adjusting higher rates than the ideal rate may be okay. Lowering the spring rate beyond the recommended rates will cause a lot of stress on the shocks, because it is providing more resistance than the springs, and most likely will cause more ware & tear on the shock or other suspension components. .

11. What is the advantage of lighter spring weight?
It seems like I can lighten up my car a little only.

Any weight under the suspension is called (un-sprung mass).
Depending on situation, un-sprung mass is equal to 5-7 times the sprung mass (weight above suspension). For example, lighten the suspension by 2 lbs per spring actually equals to removing 40-56 lbs of equipment removing from interior.

Have you ever notice that you feel less power, worse ride quality, and you get worse gas mileage when bigger (heavier) wheels and or tires are installed? How much you feel in this situation all depends on how heavy they are, and also, other reasons like lower profile tires, you get those effects because of un-sprung mass. Other than that effect, lighter springs have faster reaction. Faster spring reaction absorbs bumps on the road and other harsh conditions faster (tires can stick better on pavement), and smoother, therefore, you get better ride quality, and easier on tires..