2003 Honda Accord -- Chassis

7/29/2002 2:06:58 PM

In developing the '03 Accord chassis, Honda engineers took on the challenge of providing both world-class dynamic performance and ride comfort. Balancing world-class levels of ride quality, cornering prowess, steering and braking response into one versatile midsize package was no easy task. Establishing the parameters entailed benchmarking an international field of vehicles with the goal of providing a new, more exciting driving experience for Accord owners. Meeting those parameters called for enhancing some areas of the already popular Accord chassis, and a new take on others.

The new Accords retain the basic double-wishbone suspension design that has long made it a favorite. As before, the rear hardware employs an additional multi-link configuration that adds a supplemental lateral link for improved toe control. A totally new front sub-frame, refinements to the front suspension geometry and refinements to the rear sub-frame stiffness and suspension geometry provide a more sophisticated overall character, enhancing body control under acceleration/deceleration, high and low cornering loads and in transient maneuvers. Despite its greatly expanded dynamic envelope, these changes also yield significant improvements in both ride quality and overall isolation.

Accord Chassis Highlights

Improved, Linear Steering

  • Rack and pinion power steering system incorporates new orifice type steering damper for improved high speed feel
  • New steering kickback reduction valve improves steering feel particularly during cornering
  • Improved suspension geometry and body rigidity helps sharpen steering response

Braking

  • Larger front disc brake rotor diameters (all 4-cylinder models and V6 Coupe with manual transmission)
  • Electronic Brake Distribution (EBD) on all Accord models with 4-wheel disc brakes (EX 4-cylinder, all V6 models)
  • ABS is now standard on all Accord models
  • A new Traction Control System for V6 models integrates full-range Electronic Throttle Control (ETC) into a system that reduces wheelspin and improves vehicle dynamics at all vehicle speeds
  • New lightweight, high-efficiency master cylinder
  • New 10-inch brake booster replaces previous 8- and 9-inch tandem setup
  • Pedal feel improved-more positive action
  • Pedal stroke distance reduced

Ride, Handling and Stability

  • All new powertrain mount system provides optimum NVH benefits along with ride and handling enhancements (see NVH section)
  • Revised front suspension geometry slightly lowers the roll axis and improves anti dive/squat characteristics
  • Stiffened rear sub-frame with revised geometry raises the roll axis and increases anti lift characteristics
  • Better roll/pitch control
  • Larger wheels and tires on all models
  • Larger, high-compliance bushings in front lower control arms reduce impact shocks

Chassis Components

Enhanced Geometry
Improving the new Accord's dynamic capabilities entailed significant revisions to its suspension geometry. These modifications were intended to impart a more sophisticated overall character, enhancing body control under acceleration/deceleration, high and low cornering loads and in transient maneuvers as well as improving stability in cornering.

This comprehensive recalibration process involved changing control arm lengths and locating points on both ends of the car. Up front, this resulted in a lowering of the roll center height and a lengthening of the virtual roll arm length. In the rear, roll center height was raised and the virtual roll arm was lengthened. The rear toe curve also was modified.

Collectively, these changes have transformed the Accord's driving dynamics. With steering response quickened and roll and weight jacking curtailed during spirited cornering, the car feels much more planted and balanced. The revised suspension geometry paid similar dividends in reducing the Accord's pitch tendencies. By increasing the front anti-dive/anti-squat and rear anti-lift angles, these undesirable weight transfer motions were reduced by 25 percent under braking and by 29 percent under acceleration.

Double-Wishbone Front Suspension
A key contributor to the Accord's new ride and handling balance is its front double-wishbone suspension. This latest expression of Honda's suspension technology is an evolution of the system used on the previous Accord. The system is comprised of a large lower arm that pivots from the front subframe, with a smaller upper arm that's positioned above the wheel and tire and wraps around the spring/damper unit to pivot on the mounts in the unibody structure.

The front suspension geometry has been reworked to impart a more sophisticated overall character, enhancing body control under acceleration/deceleration, high and low cornering loads and in transient maneuvers as well as improving stability in cornering. 

Five-Link Double-Wishbone Rear Suspension
The Accord's subframe-mounted five-link double wishbone rear suspension is designed to provide precise camber and toe control, exceptional ride compliance and good space efficiency. The system consists of a series of tubular steel links that precisely position the upright that carries each rear wheel through its full suspension motion. The upper and lower links control camber when cornering, so that the tire contact patch remains flat (the optimum position for maximum adhesion) throughout the wheel's range of movement. The lateral links compensate for the inherent toe deviation of independent rear suspensions, which tends to steer the car as it corners (roll steer). As a result, the Accord tracks accurately around curves with no noticeable roll-steer effect.

See the "Body" Tab for more information on the Accord's NVH control features.

High Capacity Front Compliance Bushings
New and substantially larger compliance bushings fitted to the Accord's front lower control arms help improve overall comfort by allowing significantly more fore and aft "give" in the front suspension. On small bumps, pavement seams and patches, the performance of these new bushings is a critical component of overall ride quality and road isolation. 

Rack and Pinion Steering With Improved Stability and Reduced Kickback
The Accord's well-weighted and highly responsive power rack-and-pinion steering system provides an exceptionally linear and consistent feel regardless of pavement conditions. The Accord's power assist is steering-torque sensitive; hydraulic boost is applied to the system in direct proportion to the amount of force (torque) created between the tire and the road as the wheel is steered.

As the force increases, the system increases the amount of power assist accordingly. Regardless of speed, an increase in effort is countered by an increase in boost (for example, if the wheels encounter a rough surface with a greater coefficient of friction).

To provide the Accord's steering with a high level of useful feedback without excessive harshness, the system incorporates two new features. The first is a steering damper that smoothes the level of assist provided by the power steering pump, with the benefit of improved steering stability at higher speeds and an improved "feel" throughout all speeds. A kickback reduction valve also has been added to reduce harsh feedback felt through the steering wheel over rough or uneven surfaces, especially during cornering. With conventional steering systems, steering kickback increases in intensity as lateral g-forces and steering torque increase. The Accord's new system substantially reduces the rate of kickback increase.

Upgraded Braking Systems

Stopping power has been enhanced across the Accord lineup. In addition to multiple hardware refinements that enhance stability and help trim braking distances, both the Sedan and Coupe now boast best-in-class pedal feel and stroke. ABS has been made standard equipment on all Accords.

Other key changes include a single, high-efficiency 10-inch booster in place of the 8-inch/9-inch tandem unit used previously; a lighter, more efficient master cylinder; and a new front disc package with increased rotor sizes. On 4-cylinder Accords, the diameter dimension rises from 10.2 to 11.1 inches, equal to that found on automatic transmission V-6 models. That spec jumps from 11.1 to 11.8 inches on the V6 Coupe with 6-speed manual transmission.

Precision optimization of mechanical and hydraulic pressure ratios in the new system yields major improvements to the pedal feel and stroke under both low- and high-effort stopping situations. Brake stroke on the new Accord has been reduced by 11 percent compared to the 2002 model and is now comparable to the best European cars.

ABS
The new Accord's standard ABS system employs four wheel-speed sensors and three control channels. The speed sensor at each wheel sends signals to the ABS control unit, which in turn independently modulates the brake fluid pressure to each front wheel and the rear wheels in tandem. This system enhances the driver's ability to maintain steering control during hard stops on all types of surfaces. The ABS function is particularly effective on split-friction surfaces in which the wheels on one side of the vehicle have significantly less traction than those on the other side.

Electronic Brake Distribution (EBD)
The new EBD system used with 4 wheel disc brakes (EX 4-cylinder and all V6 models) complements the function of the ABS by adjusting braking force front-to-rear depending on passenger (or cargo) positioning to deliver enhanced stability and stopping performance. When brake force is applied, the ABS computer's EBD function estimates the proper distribution of braking pressure based on the difference between the front wheel and rear wheel speeds. Hydraulic pressure to the rear wheel brakes is adjusted via the oil pressure controlling actuator. With a heavy payload under hard braking, the maximum amount of braking force is applied to the rear wheels.

V6 Traction Control System
A new, state-of-the-art traction control system is standard equipment on all V6 Accords. Computer controlled and driver-selectable, this new-generation TCS improves Accords handling, stability and traction at all speeds and with all types of low-grip road conditions. Unlike the previous system that only interfaced with the Accord's ABS circuitry at speeds under 25 mph, this new-generation TCS also incorporates full-range throttle control that prevents undesirable wheel-spin regardless of vehicle velocity and extends active braking control up to 53 mph.

Increased Tire Sizes
To take full advantage of their improved dynamic capabilities, all Accords are now fitted with larger, more performance-oriented all-season tires that enhance ride and handling characteristics. These upgrades appear on both 4-cylinder and V6 models. The most dramatic change is found on the EX V6 Coupe, which is shod with 215/50R17 rubber when fitted with the new 6-speed manual transmission.

Accord Sedan Tire Sizes

'03 Accord

'02 Accord

DX 4-cylinder

P195/65R15

P195/70R14

LX 4-cylinder

P205/65R15

P195/65R15

EX 4-cylinder

P205/60R16

P205/65R15

LX/EX V6

P205/60R16

P205/65R15

Accord Coupe Tire Sizes

'03 Accord

'02 Accord

LX 4-cylinder

P205/65R15

P195/65R15

EX 4-cylinder

P205/60R16

P205/65R15

LX V-6

P205/60R16

P205/65R15

EX V-6

P205/60R16

P205/60R16

EX V-6 6 M/T

P215/50R17

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