フォーバイフォーエンジニアリングサービス : 4x4 Engineering Service

Responding to the needs of serious Jimny users

By replacing the front arm bushings, this part brings the caster angle of the lifted Jimny to the optimum angle.
Please contact your nearest dealer for more information.

Jimny Lift and the Need for Leading Arm Bushings

Benefits of Lifting

Generally speaking, when it comes to suspension tuning for four-wheel drive vehicles, lifting is the standard. The biggest advantage of this is that it increases the road clearance, which increases the three angles (*1) and improves the off-road driving performance. Of course, it also has a dress-up effect, and it goes without saying that it looks very wild and cool.

*1The approach angle (AA), deperture angle (DA), and ramp breakover angle (RBOA) are the ground obstacle angles of a car.

What happens in a lift-up

It is necessary to know the various phenomena that occur in changing the values pre-set by automobile manufacturers correctly.

（1）Axle misalignment

Due to the structure of the Jimny, raising the ride height will cause one wheel to go inside the body, while the other wheel will try to protrude outside the body. Depending on the tire size, the wheel may protrude from the fender, which may cause the vehicle to not meet vehicle inspection requirements. The arm and spring will also tilt to the left or right.
To deal with these problems, it is possible to correct them to the proper position by replacing the lateral rod with an adjustable type.

（2）Higher center of gravity

By raising the center of gravity of the vehicle, the roll axis rises, which increases the anxiety factor for cornering. It is possible to reduce this to some extent by changing the lateral rod installation position, or by changing the spring rate or stabilizer rate.

（3）Hoses will not be long enough.

When the vehicle height is raised by replacing the springs and dampers, the brake hoses and stays may not be long enough. Depending on the amount of lift, it may be necessary to replace the hoses and stays with longer ones.

（4）Changes in Alignment

As the distance between the body of the car and the axles and tires changes, the various alignment values such as toe, camber angle, caster angle, and steering wheel center will also inevitably change. Four-wheel alignment correction (adjustment) is essential to ensure that the car drives straight without being steered.

What is a caster angle?

This section explains the "caster angle" that has the biggest impact when lifting a rigid axle vehicle like the Jimny.
For example, if you take your hands off the wheel after turning at an intersection, the wheel will try to go back on its own and the car will try to drive straight. This is because the wheels have a "caster angle".
Let's take motorcycles as an example. Sports bikes, which excel in agile riding, and American bikes, which are designed for riding long distances with ease, have very different sensations in handling and other driving operations. Specifically, the front fork of the sports type has an upward angle (small caster angle). American type front forks are angled down (large caster angle).
The difference between the sports type, which is good at cornering, and the American type, which has excellent straight-line stability and a relaxed ride, is mainly due to the difference in caster angle.
Incidentally, it can be said that the reason why a "unicycle" is dizzy and difficult to go straight is because it has no caster angle at all (0°).

Correct the caster angle of the Jimny.

In the case of Jimny, which is a rigid axle (hosing) vehicle, the hosing will be tilted and the caster angle will be reduced due to the lift-up. This will result in low straight line stability, wobbling on the highway, and steering wheel failure.
In the case of JB23, JB64, and JB74, there is a method to correct the inclination of the hosing by replacing the bushing of the leading arm with an eccentric type. By offsetting the hole position of the bushing, the hosing mounting position is shifted up and down.

Measured value of change in caster angle

The actual measured values when our 30mm lift-up coil is installed are as follows. There are two front and two rear leading arm bushings for the left and right side, respectively, and by replacing both the front and rear bushings (4 bushings in total), it is possible to correct to the stock standard value.

Ride height + correction	Measured caster angle	Amount of change from stock	Eccentric bushing correction effect
Genuine standard value	2°07'	0	---
30mm lift + no correction	-0°47'	-2°54'	---
30mm lift + 1 eccentric bushing in front (2 total)	0°35'	-1°32'	1°12'
30mm lift + 2 eccentric bushings front and rear (4 bushings total)	1°55’	-0°12’	1°19'

If the Jimny is lifted by 30mm and the eccentric bushings are not used, the caster angle will be too small. By using 2 eccentric bushings for each side of the hosing fixture, the caster angle will be almost back to the stock standard value.

LEADING ARM BUSHING(for JIMNY)