Maruha BC Damper Kit :Bearing Ball Upper Mount Version

Maruha's BC Damper Kit, which is a bearing-ball upper mount design, makes street drive comfortable and allows moderate grip on circuits. This product covers all of the MIATA NA and NB series.

1. The kit's contents and functions

This kit is a MIATA suspension system developed by Maruha.
We design or adjust the bearing ball upper mount, the stroke, the body case, the damping force, the gas pressure and so on.

The product contains a bearing upper mount for increasing the stroke, a spring (spring rate: Front 8.0kg/mm, Rear 6.0kg/mm), a damper body and some accessories.

The body case is a single tube shell case that can radiate heat immediately.
It is made of off-black plated drawn steel wire to achieve low-friction and anti-abrasion feature of a piston.
This piston's diameter is 46.0mm, which is the largest in the line of the MIATA series and its durability and capacity are excellent.

The aluminum bearing ball upper mount is being machined specially for this product.
Because the bearing ball made in Japan has excellent quality, you can steer smoothly keeping high durability.

The function of the BC Damper consists of an adjusting bracket (overall height adjustment system) and a 15-speed adjustment click shock absorber.

The 15-speed adjustment click shock absorber adjusts damping force at the top of the click shaft and you are able to use it for cross-ridges and circuit drives.
The shock absorber can withstand until F 12.0kg/mm and R 10.0kg/mm in hard drives, while in street use, F 4.0kg/mm and R 4.0kg/mm (basic rates are F 8.0kg/mm and R 6.0kg/mm).

The adjusting bracket, which is an overall height adjustment system placed on the bottom of the damper body, can finely adjust the car height even though there is no spring allowance without helper springs.
This system prevents the springs from excess loads and allowances.
It adjusts from low positions in time attack to street positions.

2. Get more stroke! : upper mount

Our upper mount is designed by us and is made with billet aluminum.
To maintain the stroke rate, the front and rear of the product are machined to unique shapes.

The MIATA lacks stroke and it is the same with any suspension of the car.
In order to solve this problem and to increase the stroke, we improve the shell case length, the rod length, and the upper mount bearing support.

Certainly, the short stroke of the MIATA might be a real headache to you.
While we ease your worry, Maruha BC Damper can also match the needs of many street users who drive the cars in the lowest height on the street.
Consequently, our BC Damper has enough stroke to make your drive more enjoyable.

3. More durable rod

The rod, including the adjusting shaft and the damping shaft, has a 15-speed adjustment click shock absorber on the top of it.
We make the rod diameter larger to get enough strength.

4. Why are the spring rates F 8.0kg and R 6.0kg?

You might know that “F 8.0kg and R 6.0kg”mean the basic spring rates of the BC Damper.
The spring rates can work the spring to display its real ability both in comfortable street drive and in severe sports drive by improving the gas pressure and the shim stack.

The features of the spring you will want in street condition are not only to avoid rough handling, but also to gain more user friendly steering and strokes.
To meet the requirements, Maruha keeps enough roll for drivers to handle your cars without any troubles.

In a time attack, the low form and the damping adjustment bring fulfilling grip and quick steering.

5. Car height adjustment devices

Height adjustment area

Adjusting bracket

The spring lower seat, which is made of aluminum, moves about 2.0mm up and down at one revolution.

Once you have got a Maruha BC Damper Kit, our spring lower seat offers you fine opportunities to enrich your car.

The spring lower seat has not only the role to avoid the spring allowance but also gives you a great chance to arrange the spring preload as freely as you wish by using the adjust bracket together.
Whenever the lower seat and the adjusting bracket, so called an overall height adjustment system placed on the bottom of the damper tube, are used you can adjust the spring preload without changing your car height.

Moreover, higher spring rates are available through tightening up the lower seat.
You won't ever need to change the spring.
But then, you will find your car height higher.
What's the solution?
We recommend to lower it with the adjusting bracket.

If you make full use of the spring lower seat, you will get a more exciting experience of suspension tuning.

6. Bottom bush

Our bottom bush is made of urethane rubber and you do not have to worry about the damage due to the weight on it.

7. Accessories

A.Wrench set for car height adjustment

PENETRATE LUBE, which is an anti-corrosion penetrating fluid, keeps a long lasting protective coating to free the shell case threads from rust and dirt.
This product is also an accessory of Maruha Racing Thread Control Kit.

If you are interested in a more street-oriented damper, visit “Maruha BC Damper Kit: the Genuine NB Upper Mount Version” page.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312