1987 Acura Legend Coupe Chassis
The performance potential of the Legend Coupe required a fully independent suspension system that would provide excellent directional stability and control over a wide variety of road surfaces, speeds and conditions. It was designed to provide good road feel and responsiveness as well as a high degree of passenger comfort. Stiffer front and rear springs and dampers are used than on the 4-Door Sedan to improve handling and transient response.
The Legend Coupe uses a double wishbone front suspension. It has a number of advantages: low shock absorber friction; improved camber control; and a compact design which allows more underhood space and a lower hoodline. It also minimizes toe change and bump steer under load and over uneven surfaces.
With the double wishbone system excellent camber control is possible and the shock absorbers, as they are not load-bearing, operate more effectively. The upper arm is angled for proper anti-dive control. For added high speed directional stability, caster trail was increased from 8.8 to 11.3mm. Toe change is minimized by a high degree of parallelism between the lower control arm and tie rod.
A major difference between the Coupe's and the Sedan's front suspension is the use of ball-end instead of bushed stabilizer bar links. They provide less friction and quicker response than rubber bushings because there is no deflection under load.
Also, the Coupe's wishbones are mounted lower to drop roll center heights. This decreases understeer and promotes more neutral handling characteristics.
The Legend Coupe's rear suspension is fully independent. It uses double wishbones and a trailing arm. The spring/damper unit has no locating function which reduces damper friction, making it possible to tune damper rates more precisely.
Rear suspension geometry incorporates built-in camber change to improve cornering power by keeping the wheel/tire more perpendicular to the road surface. This design also reduces lift under braking. Rear tread is 40mm wider than the Sedan's.
The Legend Coupe uses power assisted rack-and-pinion steering with a quick steering ratio of 15.9:1, 3.03 turns lock-to-lock, and a turning circle of 11.12 meters (36.5 ft.). The system is road-speed sensitive in that power assist progressively diminishes as speed increases: maximum assist is available for low speed maneuvering and parking, while at cruising speeds assist is reduced to maintain road feel. For driver comfort, the steering column is adjustable, except in SRS equipped versions.
The Legend Coupe is equipped with four-wheel disc: brakes. Power assist is provided by a 10-inch vacuum servo, unit, and the braking system incorporates a proportioning valve. Dual diagonal hydraulic circuits are used to prevent the total loss of braking power. In the event of hydraulic failure in one circuit, one front brake and its opposite rear brake remain operative.
The 282 mm (11.1-inch) diameter front discs are vel1tilated; the 260 mm (10.2-inch) diameter rear discs are solid and the rear brake calipers incorporate a mechanical parking brake. Total front brake swept area is 1399.4 sq. cms (216.9 sq. in.) and total rear brake swept area is 1106.9 sq. cms (171.6 sq. in.).
The Legend Coupe's Anti-Lock Braking (ALB) system is covered in the ALB/SRS section.
WHEELS AND TIRES
To complement the Legend's power and handling capability, performance-oriented Michelin MXV 205/60 VR15 radial tires are used. They're mounted on unidirectional, light alloy, 5.5JJ x 15 wheels.