Overview
The RL is equipped with 4-wheel independent double-wishbone suspension with coil springs, 4-wheel disc brakes with ventilated front rotors, an Acuradesigned Anti-Lock Braking System (ABS) and stabilizer bars both front and rear. The goals used in developing the RL chassis were to increase overall cornering ability and to make the response of the chassis to driver input as linear and predictable as possible, while at the same time achieving a smooth, well-controlled ride-and reducing noise, vibration and harshness to a remarkable degree.
Low-Friction Double-Wishbone Suspension
The double-wishbone suspension layout of the RL (and all other Acura automobiles) allows precise control of wheel movement, while isolating the damper units from the side-loading and resulting friction inherent in the less advanced McPherson strut design used on some other luxury sedans. The front suspension uses unequal-length upper and lower control arms and a tubular stabilizer bar, while the rear suspension is a combination of a longitudinal trailing arm, three lateral links and a tubular stabilizer. For excellent stability and improved ride quality, added anti-squat and anti-dive geometry were built into the RL suspension. To achieve a compliant ride without compromising handling response or cornering capability, the RL suspension also uses a number of innovations to reduce friction throughout suspension travel. The stabilizer bars use highly efficient ball joints at either end, as well as selflubricating bushings at the sub-frame mounts. The upper arms of both the front and rear suspension have low-friction ball-joint bushings where they attach to the main structure, reducing overall friction while enhancing rigidity of the suspension assembly. The dampers of the RL have an advanced Progressive Valve design, for increased damping control at low damper speeds while retaining quick, fluid response to large impacts. Special, redesigned Teflon seals within all four damper units reduce friction even further, for improved ride quality.
Low Roll Center
To give the RL a stable, predictable feeling during hard cornering, while improving overall lateral acceleration capability, the suspension geometry was designed with lower roll centers than previous Acura luxury sedans. Roll center of the front suspension is 59mm above ground level, and 70mm above ground level at the rear. This has resulted in higher ultimate cornering performance, from 0.77g to 0.80g,as well as more predictable response at the limits of adhesion.
Liquid Rear Trailing Arm Bushing
To reduce road noise and harshness, the bushing at the front of the rear trailing arms is a liquid-filled design, instead of the more conventional rubber-damped bushing.
Braking System
Power-assisted four-wheel disc brakes are standard, with ventilated rotors in front for minimal fade and excellent heat dissipation. Front discs are 280mm in diameter; rear discs are also 280mm across. By fine-tuning the leverage ratio of the brake pedal and the response characteristics of the power-brake vacuum diaphragm, the RL engineering team achieved reduced stopping distances while making brake response more linear and intuitive. Combined with the new "low-creep" torque converter, these refinements also help make it easier to hold the RL at a stop.
Anti-Lock Braking System
A three-channel, four-wheel ABS system is standard. The ABS enhances steering control during hard braking. Speed sensors at each wheel send signals to the ABS control module; if the system detects impending wheel lockup, if first holds, then reduces hydraulic pressure to the affected wheel, letting it regain traction before full braking resumes. The ABS function is also highly effective on split-friction surfaces, in which one side of the vehicle has significantly less traction than the other. In the highly unlikely event of an ABS failure, a warning light is illuminated on the instrument panel. In such a case, the control module cancels the ABS function, allowing the standard braking system to operate normally. The system used in the RL is a new design which weighs 1.3kg less than the previous-generation ABS system.
Rotary-Valve, Variable Power-Assisted Rack-And-Pinion Power Steering
A new rotary valve senses torque applied to the steering wheel and varies power assist accordingly. This valve, in concert with inputs from a speed sensor, adjusts steering assist for easy steering in parking-lot conditions and quick, precise steering feel at speed.
Wheels And Tires
To reduce unsprung mass and to enhance cornering power and handling precision, the RL is equipped with 6.5JJ X 16 cast-aluminum wheels and P215/60 R16 Michelin tires. The tires of the RL are of a special low-rollin gresistance design, which yields outstanding ride characteristics and improved fuel mileage, while achieving excellent handling response and overall grip. The tires are an All-Season design, for enhanced traction on wet roads as well as on dry pavement.