http://www.mynismo.com/products/?id=5957

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FAQ (coilovers for street drivers & track racers)
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.


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

History of the company that is manufacturing the springs (do they have experience behind there technology)? Where the product is actually manufactured at? What material that the product is made out of? How much available stroke the spring possesses, the rating, and the lifespan of the product? We have over 85 years of experience in spring manufacturing history.



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.



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.


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 weight transferring from side to side should be very smooth and controllable. After learning the cars 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 thought most of the compression 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 transfer.

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.



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.



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 Freelength of the spring you have and round it to the nearest inch.
Spring rate should be provided by contacting the manufacturer of your system. Many brands also print the spring rate on the spring somewhere. Depending on manufacturer and model this rate and size may be different.



How much can I adjust a spring rate?

Depending on manufacturers and models. For a basic guideline, you should not increase or decrease the spring rate more than +/-4kg (225lbs/inch) from systems stock rate. High end Motorsports coilover systems may be able to be customized further but you should speak with your manufacture about the tolerance. Otherwise, you may speed up the wear on the valving. If you are willing to have your shocks inspected and revalved regularly, adjusting rates higher than the ideal rate may be okay. Lowering spring rate beyond that if you are willing to revalved, will cause too much stress on the shock since it is providing more resistance than the springs, and most likely will damage the shock or other suspension components.



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 (unsprung mass).
Depending on situation, unsprung 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 40-56lbs 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 Unsprung mass. Other than that effect, lighter springs have faster reaction. Faster spring reaction absorbs road bumps and other conditions faster,(tires can stick better on pavement)
and smoother, therefore, you get better ride quality, and easier on tires