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SUSPENSION

STRUCTURE

The single tube type is usually for racing specification. Why does HKS make it for street specification?

HKS' goal of suspension development is to have a perfect damping force in every situation of the driving environment. That's why we make our suspension in a single tube model. It's true that the single tube type was born in the racing world. It also means that single tube type is the best for the driving a automobile. Because the racing world is the toughest driving environment, it proves the single tube to be the best. That's why HKS choose the single tube type for our suspension.
However, they are costly structure to produce and difficult to design. That's why many other suspension makers gave up on this type of suspension production. But, HKS has everything from designing to packaging which make it possible to produce great products at a lower cost.

I heard that the single tube type cannot have enough stroke volume compared to multi tube type. Doesn't that mean the single tube type is less comfortable than the multi tube type?

It is true that the multi tube type has more stroke volume than a single tube type. But, it doesn't mean the bigger stroke volume has a better suspension performance. The single tube type has two rooms of oil and gas, and the piston moves inside the oil chamber which produces an ideal damping force. The cylinder is in the outside of a chamber so the oil lasts long which results in a longer life of the suspension.

Is it true that the single tube type is less durable against outside impact than the multi tube type?

It is true that the single tube type is less durable than the multi tube type. However, the roads in these days are paved, and it does not usually happen that something may cause the suspension to break. Also, HKS makes the suspension with very hard materials. So we are sure HKS suspension is safe to install.
Then what the impact from the side?
Single tube type is an inverted type. It can be durable against the impact from the side.
The single tube type needs very detailed work in a seal. This kind of precise work can produce a strong and safe suspension.

What is the piston valve? What are the advantages?

Piston valve is the part in the tip of the piston rod. It moves up and down while driving, and the oil flows into the piston and orifice that is a hole oil flows in. The piston valve is the heart of the damping. When the damper gets a force from the road, the piston goes up and down inside the cylinder, and it generates a damping force by the flow of the oil.
By setting the volume of the pressure, oil flow and valve timing control the oil flow. This is the most difficult step in developing a suspension. There are totally different settings for each situation like D1 drift, street drive, circuit race, drag, etc.

How does the oil flow passage effect on the damping force?

With the single tube type, a piston area can be enlarged. Enlarged piston area can increase oil flow passage. Increasing oil flow passage allows smoother oil flow and enables the damper to generate proper and stable damping force. However, just increasing the oil flow passage does not deliver efficient oil flow. It is important to calculate the best oil flow passage for more efficient oil flow by figuring out the best balance with other internal parts. As mentioned in Q4, maintaining the best oil flow is very difficult. The oil flow passage shape must be designed exclusively for each vehicle model based on each damping force characteristics; therefore, there is no perfect flow passage shape. As long as pursuing for "Feelable Performance = Ride Quality", further improvement of the flow passage shape should be sought.
For those who get tired of ordinary feeling from the stock suspension, various ride feeling must be offered. To deliver ride quality as a driver desires, it becomes a key to arrange the ride feeling.

For Sporty Driving

It is my first time to purchase a sport suspension. I am looking for a sport suspension that can lower the ride height, but the ride quality is still high for daily driving as well as circuit driving. Which type of HKS suspension is recommended?

No extreme low-stance, but moderate low-stance, a good ride quality for daily street driving, and sportiness and supple ride quality while driving on winding roads or cornering at a high speed; these are the required characteristics.

→ MAX IV GT is recommended. This is an ultimate street suspension that lowers the ride height for stylish appearance and provides a good all-round performance.

I am looking for a suspension for high performance sport driving in a circuit using high-grip radial tires with a good ride quality. Which type of HKS suspension is recommended?

A suspension surely informs a driver of road surface conditions through tires and shows high performance during severe cornering; additionally, comfortable ride without annoying thrust feeling is wanted while going to a circuit.

→ MAX IV SP is recommended. This is a shock-body length adjustable sport suspension that is appropriate for high performance sport driving and reduces the unwanted thrust feeling.

I bought a luxury car for my family. Which type of HKS suspension is recommended for mature and sporty performance?

Better ride comfort for street driving, supple but reliable driving performance while driving on winding roads or cornering at a high speed and the ride height for stylish appearance are required characteristics.

→ MAX IV GT is recommended. This is a luxury sport suspension that is designed according to each vehicle's characteristics for the best settings for each vehicle model.

I am a drift enthusiast. I am looking for a suspension designed especially for drifting

Usually, a suspension for drifting is stiff making it easy to lose the traction. However, it won't allow maintaining high speed and performing a long drift at the right angle. With enough traction to sustain the vehicle movement, suspension should provide a driver with ability to have a complete control over the vehicle.

→ HIPERMAX D' NOB SPEC is recommended. This is a suspension that is able to maintain high speed while drifting, and at the same time provide enough traction and ability to control a vehicle. DNOBSPEC concept is a suspension to make drifting easy for anyone.

For Mini Van, Wagon, and Compact Cars

I bought a wagon for my family. I am looking for a suspension that can lower the height slightly for better stance and offer a comfortable ride. Which type of HKS suspension is recommended?

What you are looking for is a suspension that can adjust the ride height as you like and provide stable driving performance during changing a lane, passing over the joint of the road, and going down a slope while braking.

→ HKS is offering HIPERMAX G, HIPERMAX S-style C, and HIPERMAX S-style L.
The vehicle appearance, better ride comfort and driving stability after installing this product are satisfiable for minivan and wagon owners.
HIPERMAX G is the OEM design suspension, HIPERMAX S-style C is the shock—body length adjustable type, and HIPERMAX S-style L is 30-way adjustable dampening type.

What are other advantages of modifying a car to a lower stance besides improving its appearance?

Modifying a car to a lower stance can improve handling because the unstable behavior of a car can be reduced; therefore, a driver does not get too tired after long distance driving. Also, it may restrain and/or prevent carsickness of vehicle passengers in second or third-row seats. As another advantage, lowering a vehicle height allows the easy getting-on/off of a vehicle.

Compact car is usually economical and good for street driving as well as sport driving. Which type of HKS suspension can derive its original advantage from the stock suspension of a compact car?

To utilize the original advantage of a stock suspension, the vehicle height should be adjusted to a preferred level to improve its footwork, and there should be no upthrust or floating feeling.

HKS Hipermax S-style C is best for a compact car; S-style C can provide better ride comfort and has appropriate characteristics not only for street driving but also for sport driving.

Larger wheels, aero parts, and low stance give wagon cars a more aggressive appearance; but, there is a risk of damaging the wheels or aero parts by lowering the vehicle height. Which type of HKS suspension can avoid this risk?

To improve the appearance of a minivan and wagon car, the aero parts, larger wheels, and low stance are must-have items. But, for a minivan or wagon car with the aero parts and larger wheels, the vehicle height must be lowered properly to maintain the ride comfort and its style, and the damping force must be properly adjusted to avoid excessive stroke that may cause damage to the aero parts and wheels.

HKS Hipermax S-style X is the one for cool low stance. S-style X can adjust the vehicle height properly, and its damping force is adjusted properly so there is no risk of damaging the wheels or aero parts by lowering the vehicle height.

SOUND

There is a strange sound from the suspension.

* Please consult with the shop or specialist about possible causes of the noise.
Do not attempt to repain by yourself.

Overhaul & Specification Change

I am using Hipermax damper. Recently, it does not respond well, and there is a strange sound from the damper. Is it time for an overhaul on the damper?

Yes, we recommend an overhaul for your damper. Also, overhaul is recommended when unsteadiness during lane change on highways and/or oil leakage is noticed.
Suspension uses many consumable parts, and several ten thousands of times strokes in driving distance of one million kilometers constantly generate and radiate heat, which cause degradation of oil and sealing.
To maintain the high performance of HKS suspension, we provides overhaul service.

Is spring rate change of Hipermax series available?

The spring rate change for the straight spring and barrel spring is available.
Please see the table below for the rates available to change.
※For some models, the springs are designed exclusively for the applicable vehicle models.  In this case, spring rate change is not available.

●HIPERMAX SERIES Spring Rate Change List

Spring Rate
[N/mm(kgf/mm)]
Free Length [mm]
Straight Spring Barrel Spring
120 150 170 200 250 200 220 250 300
29(3)        
39(4)    
49(5)      
59(6)  
69(7)    
78(8)    
88(9)            
98(10)        
108(11)              
118(12)        
137(14)          
157(16)            
176(18)            
196(20)              
216(22)                

*Circle mark (○) shows an application of the spring rate change.

  • Spring color: White
  • The spring rate change is available only for Hipermax series before shipment.
    Make sure to select a correct type of spring before selecting the spring rate.
    The spring length cannot be changed.
  • Spring rate setting for HIPERMAX series preset at suited rate for bringing out its best performance.
    Please note that the spring rate-setting except for the recommended spring rate is not covered by warranty.
    (A large spring rate change may lead to a lack of ride comfort and performance.)
  • Springs listed on the above list cannot be purchased separately.
  • The delivery date takes about 2 to 3 months since the purchase order received depending on availability.

Warranty

Does HKS provide any warranty for suspensions?

HKS provides a warranty to the original purchaser of HKS suspension against defects in materials and workmanship for a period of one year. The warranty is available only for the damper assemblies and springs. Dust boots, upper plates, pillow-ball, and hardware/accessories included in a kit are not covered.
(For more details, please go to the product warranty site.)

Vehicle Height Adjustment

Does a tire protrude from a fender after a shock-body length adjustable damper is installed to a vehicle?

When using tire wheel at the end of the fender (Tsuraichi) for the stock damper or stock type damper, the tires may come out of the fender because all usually, shock-body length Adjustable damper length adjustment type damper is larger than stock damper. After installation, it tends not to fit well for negative direction of the chamber. This symptom may be seen in the following vehicle models: AZR60(NOA/VOXY), JB5/7(LIFE), C25(SERENA), GD1(FIT). Usually, if a vehicle is lowered, the chamber tends to shift to the negative direction, and the tires move toward the fender. However, for some vehicles, a tire may protrude from a fender.