2007 Honda CR-V -- Chassis (Pt. 1)

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Overview

Honda has a legendary reputation for making its vehicles fun-to-drive with precise steering, responsive suspension tuning and refined road manners. Precise and quick handling performance also contributes to accident avoidance maneuverability - one of the key reasons Honda pays so much attention to every aspect of the suspension.

onsistent with Honda's Safety for Everyone initiative, the CR-V comes with the highest levels of chassis-related active safety equipment in the segment with Vehicle Stability Assist (VSA) and 4-channel anti-lock braking (ABS), electronic brake distribution and Brake Assist.

Every aspect of the CR-V has moved to an entirely new level from the driver's perspective. Compared to its predecessor, the 2007 Honda CR-V chassis delivers higher levels of sportiness and ride comfort with improvements focusing on enhanced suspension geometry and a lower center of gravity. The changes add up to a new CR-V that is even more responsive and sporty in demanding situations while also increasing its smooth and comfortable ride character.

New CR-V Chassis New Technology and Design

* Lower center of gravity (5 percent)
* 103.1-inch wheelbase (-0.2 inches)
* Wider track (+1.2 inches front/+0.8 inches rear)
* Front MacPherson strut design
* Larger wheels and tires
* Advanced Logic 4-channel ABS system
* Tire pressure monitoring system
* Larger 17-inch wheels (+1 inch) and 225/65R17 all-season tires (larger)
* Larger 11.7-inch ventilated front disc brakes, 12.0-inch solid rear disc brakes

Chassis Summary

* MacPherson Strut front suspension
* Multi-link rear suspension
* Standard VSA, ABS, Brake Assist and Tire Pressure Monitoring System (TPMS)
* Front and rear stabilizer bars

MacPherson Strut Front Suspension

The MacPherson strut front suspension incorporates new geometry with a high caster angle, and inversely wound springs for straight line stability, along with improved toe-control dynamics for sharp and responsive steering. To improve steering rigidity, and reduce friction, the steering gear box was mounted lower. Significant changes to steering angles, bushings, material rigidity, and spring and shock tuning result in amazingly linear suspension movement at the upper limit of vehicle dynamics and flatter cornering. When cornering, the inner wheel remains closer to perpendicular (relative to the ground plane) throughout a greater range of travel, which improves tire adhesion. To improve ride comfort, the compliance angle on the lower control arm was optimized to transmit less harshness. Further enhancements include reduced center offset with the wheel to minimize the potential for torque steer and shimmy (i.e. the tires' ability to transmit pavement irregularities into the suspension)
The front suspension is a specially designed and tuned for compact packaging, supple ride comfort and the long wheel travel and ruggedness necessary to meet harsh roads. The geometry has been optimized with both a high caster angle and "trail," to provide sharp on-center response and stability.

Additional specifics of the front suspension that help to achieve sedan-like handling include:

* High-friction upper strut mount provides a good on-center steering feel, along with increased linearity while reducing steering shimmy
* Asymmetrical coil springs improve steering quality
* Large-diameter lower arm compliance bushing reduces NVH
* Optimized kingpin layout enhances steering feel and linearity
* Large-diameter steering gearbox with rigid bushings adds stiffness and improves linear steer feel
* 20mm front stabilizer bar helps control body roll for flatter cornering

MacPherson Strut Front Suspension

Multi-Link Rear Suspension

The CR-V is equipped with a multi-link rear suspension that helps provide a smoother ride, improved handling and additional cargo space. The dynamics offered by the three-link suspension create excellent stability under cornering and braking. The independent multi-link rear suspension system with aluminum knuckle fits compactly underneath the rear seating and storage areas while providing excellent ride and handling characteristics, with low NVH. The suspension uses large-diameter trailing arm bushings to reduce harshness and improve ride comfort. Front and rear stays increase the subframe mounting point rigidity, improving stability and steer feel.
Multi-Link Rear Suspension

Rear suspension features:

* Anti-squat geometry to reduce pitching under acceleration
* 19mm rear stabilizer bar contributes to flatter cornering

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Springs, Dampers and Stabilizer Bars

The tuning of the suspension is designed to minimize front-end dive during braking and squat under acceleration, as well as reduced body roll when cornering. The spring rates, combined with precise damper tuning, provide a good balance between the CR-V's fun-to-drive character and everyday ride comfort.

As with every vehicle that utilizes a strut suspension design, the strut bears the load of the weight of the vehicle. Drive forces during the suspension's compression stage can sometimes influence steering precision feel because as the springs compress, they exert torsional force in the opposite direction on the steering mechanism and sometimes make the car pull to the side. To neutralize this effect, Honda engineers applied inversely wound (wound in the opposite direction) coil springs to the front struts. Because the two front springs compress in opposite directions, the torsional force they produce cancels each other out, minimizing their effect on steering feel.

Damper construction is a progressive valve design that significantly contributes to a smooth ride and precise handling characteristics. These gas-pressure dampers use a stacked disc-valve arrangement that yields easily and progressively to high-velocity damper piston movement, such as those created by bumps and road impacts; however, the same velocity-sensitive valves present more resistance to the small, low-velocity movement associated with body transient motion at high speed.

The CR-V has front and rear stabilizer bars to reduce body roll during cornering. The diameter of the solid front stabilizer bar measures 20 mm. The solid rear stabilizer bar measures 19 mm.

Steering System

The variable speed sensitive rack-and-pinion power steering system features quick gear ratios for sharp and rapid transitions with a quick and light response. Previously a high-mounted steering box setup, the entire steering system is located lower in the vehicle with short length tie-rods to improve input geometry (i.e. more direct) into the front suspension. A speed sensitive hydraulic power steering system provides more power boost at low speeds for easier maneuvering and less boost at higher speeds for a direct steering feel and improved economy. All models have a tilt and telescope steering wheel column. The minimum turning diameter is 37.8 feet, curb-to-curb.

2007

2006
Steering ratio, overall
15.7

16.4
Turns, lock-to-lock
2.96

3.20

Braking System with Advanced Logic 4-Channel ABS and Brake Assist

The CR-V is equipped with a 4-channel anti-lock braking system (ABS) with Electronic Brake Distribution (EBD) and Brake Assist. Stopping power is routed through robust ventilated front disc brakes and solid rear disc brakes. The 4-channel ABS with EBD independently modulates braking power at each wheel, as opposed to the more common 3-channel system that modulates the front wheels independently and the rear wheels with relatively equal braking force. The new 4-channel capability allows the rear wheels to react independently while cornering, representing a significant enhancement to the ABS system's ability to influence vehicle stability and safety.

Electronic Brake Distribution proportions brake power to the rear wheels based on algorithms that determine vehicle weight distribution. Further additions to the braking system include a new ABS control module (that applies the new 4-channel features) and a relatively large 10.5-inch power brake booster that improves pedal feel. Higher pedal rigidity with a decreased pedal stroke provides a more immediate braking response. Bottom line, the CR-V stops with greater authority and added control.

A function of the VSA system, the CR-V can also recognize emergency braking situations and enhance braking assist when needed - a function called Brake Assist. This feature can be especially helpful when the driver is unable to press the brake strongly. When the driver uses the brakes in a panic stop fashion, a pressure sensor recognizes braking system operation beyond a specific value for pedal stroke and speed. Then, the VSA modulator pump assists braking pressure to increase braking force and shorten the braking distance.

For 2007, the ventilated front disc brakes are 11.7 inches and the solid rear disc brakes are 12.0 inches. The front disc thickness equals 1.1 inches (28mm) and the rear disc thickness equals 0.35 inch (9mm).

Vehicle Stability Assist (VSA)

For enhanced control during acceleration, cornering, and sudden collision-avoidance maneuvers, the CR-V is equipped with a 4-channel Vehicle Stability Assist (VSA) system that works in conjunction with the drive-by-wire throttle and ABS systems. VSA enhances vehicle stability by applying brake force to each of the four disc brakes independently while also managing the throttle and ignition systems.

An additional benefit is the limited-slip differential effect the system provides for the front wheels by applying braking force to a slipping wheel thereby redirecting driving force to the wheel with more traction. Analyzing data that is constantly received from seven sensors monitoring speed, steering input lateral G forces, and yaw rate, the VSA system compares the driver's control inputs with the vehicle's actual response. If the actual response is outside a predicted response range, VSA automatically intervenes with an appropriate corrective action. In the case of oversteer, VSA applies braking to the outside front and rear wheels to counter the unintended yawing effect. If understeer is detected, VSA applies braking to the inside front and rear wheels and reduces engine power to help bring the car back onto the driver's intended course.

The VSA system in the CR-V has been carefully calibrated to add handling stability and predictability with minimal intrusion to the driving experience. Its operation is designed to be transparent, so drivers may not even notice when VSA is working. Whenever the system is actively enhancing the vehicle's stability, an indicator light flashes on the instrument panel. In addition, VSA's stability enhancement and traction control can be turned off with a cockpit switch while still leaving the ABS fully functional.

Wheels and Tires

The 2007 CR-V rides on 17-inch, five-bolt steel wheels as standard equipment on LX models, and exclusive alloy wheels are standard equipment on EX and EX-L models. A tire pressure monitoring system is standard equipment. The tire size is 225/65R17, representing a larger tire size that emphasizes a powerful stance.

Tire Pressure Monitoring System

A direct Tire Pressure Monitoring System (TPMS) alerts the driver when it detects that tire pressure in one or more tires drops significantly below the recommended pressure. A series of four sensors (one per tire) captures and relays information to the CR-V's ECU. If the system detects that tire pressure is significantly low, a low tire pressure indicator (located in the instrument panel meter cluster) will illuminate.

Towing Information

The 2007 CR-V has a towing capacity of 1,500-pounds. That makes the CR-V capable of pulling a small camping trailer, personal watercraft or motorcycle trailer. The CR-V can also be flat-towed behind an RV when following the proper procedures described in the owners manual.