Honda Car Forum

CHASSIS

A challenging and varied urban driving landscape steered development of the RDX chassis. In an urban driving environment, the ability to accelerate, turn and brake quickly - with stability and control - are essential capabilities. But the RDX was also designed to excel on wide-open highways, sweeping mountain roads and long stretches of Interstate.

The design goal for the RDX chassis was to provide the sporty handling of the Acura TSX sports sedan with the versatility of an SUV. These difficult goals for dynamic performance were not easy to achieve because the RDX needed a high eye-point (seating position) to provide the driver and passenger's better visibility in urban traffic conditions. However, the higher the center of gravity a vehicle has, the more difficult it is to provide responsive and nimble handling like a sports sedan.

Acura designers answered this challenge by giving the RDX a low center of gravity and overall chassis specifications rivaling those of a sports sedan. The result is an especially confident experience when changing lanes or cornering.

BEST-IN-CLASS CORNERING

The RDX achieves its mission to provide sports sedan handling while simultaneously one-upping its rivals. When tested on the skidpad, Acura internal measurements show the RDX with SH-AWD™ achieves a maximum lateral acceleration cornering force of 0.85g. This exceeds the cornering performance of the BMW X3 in the same test conditions. Much of the credit for the RDX's cornering performance goes to the SH-AWD™ system. As a result, the RDX provides sharp steering through corners, direct and linear response on winding roads and high speed stability on highways.

SUSPENSION

Acura engineers wanted to create a vehicle that transcended the traditional SUV driving experience. As a result, the RDX is at the top of its class for acceleration, turning and stopping, while delivering excellent ride quality. The SH-AWD™ system plays an important part in this, but so does the 4-wheel independent suspension, which provides compliant handling in the city and confident handling on the highway.

Front Suspension

The RDX front suspension is a specially designed and tuned MacPherson strut arrangement with compact packaging along with the long wheel travel and ruggedness necessary to meet harsh urban roads. The geometry has been optimized with both a high caster angle and "trail" to provide sharp on-center steering response and stability.

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

• High-friction upper strut mount provides good on-center steering feel, along with increased linearity while reducing steering shimmy


• Side-specific, symmetrically wound 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


• 21mm diameter front stabilizer bar helps control body roll for flatter cornering

Rear Suspension

A multi-link independent rear suspension system with aluminum knuckles fit compactly underneath the RDX's rear seating and storage areas while providing excellent ride and handling characteristics along with low NVH. The suspension uses large-diameter trailing arm bushings to reduce harshness and improve ride comfort. A special steel suspension subframe with large "floating" bushings markedly reduces NVH while maintaining stability. Front and rear stays increase the subframe mounting point rigidity, improving stability and steering feel.

Rear suspension features:

• Anti-squat geometry to reduce body pitching while under acceleration


• 19mm diameter rear stabilizer bar helps deliver flatter cornering

STEERING

The Acura RDX has quick-ratio (15.1:1) power rack-and-pinion steering for response like that of a sports sedan. The hydraulically assisted steering is speed sensing, for easy maneuvering at low speeds and maximum feel and driving enjoyment at higher speeds. The curb-to-curb turning diameter of the RDX is 39.2 feet.

To improve steering precision, a stay (or stiffener) supports each end of the steering rack, further improving steering system rigidity. In addition, the rack-and-pinion gearbox has aluminum mounting brackets that, should a severe crash occur, will allow the aluminum brackets to break off when the engine is pushed rearward into the rack-and-pinion gearbox. This breaking action helps reduce intrusion into the interior which helps to improve occupant safety.

WHEELS & TIRES

The RDX was the first Acura model with standard 18-inch wheels and tires. For 2010, the RDX comes with new 18x7.5-inch 10-spoke aluminum wheels paired with Michelin Pilot HX MXM4 P235/55R18 tires. The Michelin high-performance all-season tires are exclusively designed for the RDX, and have optimized sidewall rigidity that maintains vehicle stability in all load conditions. The low-profile tires also provide top class traction and braking in all weather conditions. In addition, an optional dealer-installed 19-inch wheel and tire package is available.

4-WHEEL DISC BRAKES

RDX features 4-wheel disc brakes with 11.7-inch diameter brake rotors in front and 12.0-inch diameter rotors in the rear. For 2010, changes to the brake booster and servo deliver even better brake pedal feel along with less initial brake "grabbiness". In addition, the brake system makes use of revised rear brake pad actuation that delivers less drag and longer pad life; also added to the mix are Geomet-coated rotors for improved looks and added rust prevention.

An Anti-lock Braking System (ABS) with Electronic Brake force Distribution (EBD) is standard on the RDX. ABS helps the driver retain vehicle control during hard braking and EBD automatically proportions brake power to the rear brakes according to the vehicle load and driving conditions, helping to improve stopping performance.

The RDX also has Brake Assist, which uses a microprocessor that recognizes the driver's intention to quickly and forcefully apply the brakes in a panic stop situation. In this case, Brake Assist immediately supplements the braking force, enabling the best braking performance in the moment when it's most needed. Brake Assist only supplements the driver's intentions, and its function terminates immediately when the driver releases the brake pedal.

VEHICLE STABILITY ASSIST WITH TRACTION CONTROL

Vehicle Stability Assist™ (VSA®) is included as standard equipment on the RDX. By continually monitoring the vehicle's operating parameters (such as vehicle speed, throttle position, steering angle, individual wheel speeds, lateral g and yaw rate), VSA® detects if the vehicle is about to oversteer or understeer. To help correct either of these situations, 4-channel VSA® automatically reduces the engine's torque output as needed, and applies one or more brakes individually, to help stabilize the chassis. The response is so quick that the instability may be corrected even before the driver knows that it is occurring. With the SH-AWD™ model, Traction Control is integrated into the VSA® to help the RDX accelerate smoothly on slippery surfaces. If required, Traction Control can be disabled.

TIRE PRESSURE MONITORING SYSTEM

Acura RDX has an onboard Tire Pressure Monitoring System (TPMS) that warns the driver if the air pressure decreases significantly in any tire. The system helps reduce the chance of damaging a tire or losing control of the vehicle due to low air pressure. This is important because a slow leak, such as one that might be caused by a nail or road debris, might not be easily detectable but could over time cause significant air loss resulting in loss of grip or potentially a blowout.

TPMS uses a sensor mounted in each wheel that continually monitors tire pressure and sends a coded signal to the TPMS electronic control unit (ECU). The process begins with a signal initiator located on the chassis just inboard of each tire. The initiator sends a unique signal for each TPMS sensor. Then the TPMS sensor sends tire pressure data to the TPMS ECU, which compares the values for each tire's pressure against an acceptable range of pressures.

On the RDX the Multi-Information Display (MID) shows the location of the tire that is experiencing significant pressure loss.

On the RDX with Technology Package, the TPMS system can simultaneously display the air pressure in all four tires via the MID, making it simple to locate a low-pressure tire.

FUEL TANK AND DRIVING RANGE

The RDX's 18-gallon fuel tank is located in a protected position under the body and forward of the rear wheels. Based on the EPA's estimated city/highway fuel economy* of 17/22 mpg (SH-AWD™) and 19/24 (2WD) means that on the highway the RDX can cover nearly 400 miles (SH-AWD™) or about 430 miles (2WD) on one tank of fuel.

*Based on 2010 EPA mileage estimates, reflecting new EPA fuel economy methods beginning with 2008 models. Use for comparison purposes only. Do not compare to models before 2008. Your actual mileage will vary depending on how you drive and maintain your vehicle.

1,500-POUND TOW RATING

For added utility, the RDX has a 1,500-pound tow rating when equipped with the available towing package. The tow rating makes the RDX capable of pulling items such as a small camping trailer, or a personal watercraft or motorcycle trailer.

ECOLOGY

Like all products from Honda of America Manufacturing's facility in Marysville, Ohio, the RDX follows strict guidelines for environmental care - both in the manufacturing process and in the actual vehicle components. The following is a partial list of significant environmental processes used in creating the RDX that reduce its long-term environmental impact.

• More than 90-percent of RDX parts are made of recyclable materials


• The use of non-chromed tanned leather (in leather-equipped models) reduces hazardous waste generation during the tanning process, and it can be composted at the end of the vehicle's life


• Elimination of PVC material in most interior parts (door lining, seat trim, shift knob, etc.) and exterior parts (roof and door moldings, weather strips and tubes) improves recycling ability


• Halogen is eliminated from fire-retardant materials


• Wheel balance weights and electro-deposition paints do not contain any lead


• Use of molded-in color plastics reduces paint emissions


• Replacement of ABS plastic with polypropylene material (such as in the center console, instrument panel and doors) reduces emissions during plastic manufacturing