Overview
Steering feel, cornering limit performance, straight-line stability.
Dual axis strut suspension realizes
World’s fastest*1 front-wheel drive at Nurburgring
The front suspension on front-wheel drive cars plays two roles: supporting the drive wheels and steering the car. With high-torque front-wheel drive cars, unexpected torque steering tends to occur, and conventional strut suspension would not provide sufficient tire grip while turning. Honda’s dual axis strut suspension separates knuckles and dampers, increasing steering axis flexibility, thus solving the problems of conventional strut suspension.
Dual axis strut suspension
(Civic Type R / Left hand drive)
Torque steering
Why torque steering occurs with high-torque front-wheel drive cars
Torque steering, the car turning regardless of the driver’s will, is unique to front-wheel drive cars with high-torque engines, and occurs mainly during acceleration while turning.
With strut suspension front-wheel drive cars fitted with wide tires, the center offset (distance from the wheel’s center (input point for engine torque) and the steering axis) is large, so sudden torque input forces the tires to change direction (torque steering). The result is sudden steering wheel movement while operating the car, such as accelerating. With conventional strut suspension, center offset is structurally difficult to reduce, and has been a problem for many years.
Adding damper fork
Dramatically reduced center offset
If there is a difference in driving force between the left and right tires during high-G turning on a race track, torque steering occurs due to imbalance in forces exerted around the steering axes. This behavior causes doubt in the mind of a driver attempting to set a new front-wheel drive record at the Nurburgring, so torque steering needed to be minimized. By adding a damper fork, Honda managed to separate the knuckle from the damper which were previously a single unit, and enable separate movement. By positioning the steering axis closer to the wheel center, a major cause of torque steering, the amount of center offset, was drastically reduced.
Conventional strut suspension has long center offset
Dual axis strut suspension adds a damper fork to drastically reduce center offset
Drastically reduced torque steering realized superb driving stability
The result was a drastic reduction in torque steering that occurred during sudden take-off or acceleration, and even with acceleration during turning, superb handling was attained through excellent driving stability and steering feel.
Suspension structure
Road holding performance
Conventional strut suspension
Loses road holding performance in high-speed turns
As large centrifugal force is applied while turning, the car’s tires on the outside of the turn tend to roll outwards, reducing the tires’ road holding performance. To prevent this, the best method is to lean on the suspension and vary the camber angle to keep the tires perpendicular to the road. The problem with conventional strut suspension was that the amount of camber variation was small, which limited the degree of road holding performance that could be attained.
Difference in turning performance according to road holding
Adding damper forks, optimizing caster angle
With conventional strut suspension, the damper axis and steering axis is the same angle, due to its structure. With dual axis strut suspension, the added damper fork separates the two axes, allowing more freedom in setting the steering axis. By tilting the steering axis back further than a conventional suspension, a larger caster angle could be set.
Conventional strut suspension with identical damper axis and steering axis angles
With dual axis strut suspension, steering axis tilts further back than the damper axis, enabling a larger caster angle
Better road handling dramatically improves
Cornering limit performance and high-speed straight-line stability
By increasing the variability of camber while turning, road holding while steering is improved, and by optimum damper axis angle setting, enabling ideal contraction characteristics. This resulted in dramatically improved cornering limit performance, and also drastically improved high-speed straight-line stability.
Conclusion
Contributing to achieving the monumental task of becoming the fastest*1 front-wheel drive
Torque steering and road holding performance during turning were issues for a long time, when developing higher performing front-wheel drive sports cars.
These issues have been overcome thanks to Honda’s dual axis strut suspension.
By separating and optimizing the axes for steering and maintaining the car’s ground clearance, torque steering has been dramatically reduced, and cornering performance has been drastically improved. These advantages are the unique features of the dual axis strut suspension.
The 2015 Civic Type R (FK2) and 2017 Civic Type R (FK8) are equipped with dual axis strut suspension, playing a large role in achieving the fastest*1 lap time*2 for a front-wheel drive car at the Nurburgring.
*1 Honda research. 2015 model as of September 2015, and 2017 model as of April 2017.
*2 2015 model lap time: 7 min 50.63 s (timed in May 2014). 2017 model lap time: 7 min 43.80 s (timed in April 2017). Both times by Honda, using pre-production development models.
