What's important
when selecting coilover kit!

1  2  Next
Coilover kit is the most popular and widely chosen item from sport cars, compact cars, to minivans and wagons, to adjust the vehicle height to your preference. Its basic function is not only to lower the vehicle for cool looking, but to improve the performance. So there are so many different kinds of coilover kit available on a market. Today, let’s see what’s important when you choose the coilover kit, and find what is most suitable for your purpose. SECRET TO ADVANCED
These are the points!
Point 1 Choose žFully ThreadedÓ coilover kit. I will tell you the secret!
Adviser for today's topic is Yuya Sumiyama. He is participating in, and one of the top drivers in JRC (all Japan Rally Championship) national series, as a driver of Cusco Rally team. As he is in charge of R&D division in Cusco, and competing through out the championship, he must be the best teacher for this topic. He knows what the drivers want, from daily street use, to the top competition use.
Cusco Yuya Sumiyama
Point 1 Choose žFully ThreadedÓ coilover kit.
Fully threaded coilover kit
Traditional partially
threaded coilover kit The biggest difference between those 2 kinds is how they adjust the vehicles height. On fully threaded models, height is adjusted at the lower bracket, while the traditional ones do at the spring lower seat rings.
This difference results in the other difference. Changes in height will affect in the damper’s stroke or not.
Most of the coilover kits in the market are either of the traditional “threaded type”, or today’s “Fully threaded type”.
Traditional threaded type is also called a “lower seat adjusting type”, and the height is adjusted by moving the spring lower seats up and down. The problem on this kind of coilover kit is: The more you lower the vehicle, the less the damper’s stroke will be. If you drive hard under such condition, you will experience full-bump/bottoming when you have huge inputs from the wheels. If the dampers are fully bottomed, those inputs are not absorbed, and hit the chassis too.
On the other hand, fully threaded type provides height adjustment at the bottom bracket. This means, travel stroke of the damper is not affected whether you change your vehicle’s height up or down. So you want have to worry about full-bump/bottoming of the damper. This fact that change in height do not affect on damper’s travel, is the biggest and most important difference on fully threaded coilover kit.
Let’s see the difference between both coilover kits. See the testing in video image
Height adjustment on
Traditional threaded type.
If you lower than certain amount, spring will be loose, and start to lose the damper strokes. Bottoming may happen as well.

Adjustment by spring lower seat.

On this type of coilover, vehicle's height is adjusted by moving the spring seats up and down. Loosen the lock nut, and screw the spring lower seats with the special wrench to the preferred height, and tighten the lock nut again. Now you are done.
Height adjustment on
Fully threaded coilover kit
Change of the vehicle height do not affect damper’s stroke, so the damper won’t hit the bottom.

Adjustment by lower bracket.

On fully threaded type coilover kit, vehicle's height is adjusted by moving the lower brackets up and down. Loosen the lock nut with the special wrench, and screw the whole coilover against the lower bracket to the preferred height. Tighten the lock nut again, and you are done.
Even at same vehicle height,
spring length and
damper stroke is different.

See how long inner shaft you see on those 2 coilover kit. Fully threaded type has longer damper stroke against traditional coilover kit. On traditional partially threaded type, you will lose the damper stroke as you lower the vehicle height.
* You do not need to disassemble or remove the coilover kit from the vehicle, when you adjust the height.
Compare the actual difference of the bump stroke on each different type.
Set zip tie on the damper rod, and see how much they travel after short driving.
Traditional threaded type
Before Driving After Driving After Driving, Zip-tie had traveled to the top, and touching to the bump rubber bushing. This means that the damper had traveled to the bottom, and also means the damper do not have enough traveling stroke.
Fully threaded type
Before Driving After Driving After Driving, Zip-tie had traveled upward, but still has some room to the bump rubber bushing. This means Damper has enough strokes, and performing correctly
Point 2 Height adjustment must be easily done at any time.

If your coilover is rusty and can not adjust the height, it does not function as a coilover kit.

If your coilover kit is rust-proof, you can easily adjust the height anytime.
As the suspension is located underneath the chassis, they are always close to the water and dust, and do not take too long to be rusty. But on a coilover kit, adjusting threads should not be rusty, and always must be “adjustable”. Being adjustable, is the most important issue on coilover kit. So you should check if they are good against rust, to enjoy the performance of the coilover kit for long period.
Point 3 Must be assembled with adjustable damping rate.
Damping rate means how much shock they absorb. When you buy the coilover kit, they are usually delivered with pre-set recommended damping rate. But when you want to change the damping rate according to the driving stages, or vehicles spec, it is very important that the damping rate could be adjusted. If it is adjustable, you do not need to buy brand new shock absorber in different damping rate, and you can use the coilover kit for longer period.

Here is your choice!
I had explained how to choose the coilover kit, and you already know them well.
You must not only see the price when you purchase the coilover kit. Even though initial cost may be bigger, but running cost will be saved in long term of view, if you choose the proper one. Buying a new one afterward will finally cost you twice.
 Now, let's see what you should choose. I will tell you what will perform for longer term, without getting rusty, and can be adjusted to suit your new tuning stages and driving environments. 
Go to next page
Back to the top