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Car Steering Takes Bold New Turn

August 27, 1987|PAUL DEAN | Times Staff Writer

Some marketing experts see it as the safest, most significant driving development since disc brakes. Others, recalling such ephemeral revolutions as the rotary engine and the digital dashboard, aren't buying the premise.

Californians will get to decide for themselves Tuesday when Honda showrooms start selling the 1988 Prelude 4WS--the first production car in America to offer optional four-wheel steering.

"We are confident it will be as accepted as, say, anti-lock brakes . . . as a growing thing until it's a fairly significant option," said Tom Elliott, senior vice president of operations for Gardena-based American Honda. In the coming model year, he said, 15% to 20% of Prelude production for the United States will be equipped with the option.

If Honda's estimates hold firm, about 16,000 Americans will buy four-wheel-steering Preludes in a factory options package that includes alloy wheels and power door locks and adds $1,400 to the car's sticker price of $16,500. In Japan, where the option has been available since spring, more than 80% of Honda Prelude buyers have purchased the handling option.

The selling point of the system is simple: Since the car's rear wheels turn to follow the front ones, the results are tighter, flatter, quicker, and at high speeds, safer turns.

Call it stereo steering.

Some companies are betting a bundle on the system as the industry lead-in to cars of the '90s. Others are waiting to see if it will survive the model year.

Mazda, whose four-wheel steering sales are also soaring in Japan, plans to introduce the 4WS Mazda 626 to the United States in October. But its initial shipment will be only 200 4WS cars a month. "We believe that four-wheel steering is indeed the wave of the future," said a spokesman, "What you're seeing from us is a very cautious, almost tentative move toward that wave of the future."

Nissan, which pioneered four-wheel steering in Japan in 1985, has sold 40,000 4WS Skylines (or 40% of the model run) since then. "But we have no immediate plans to bring it to the U.S.," a spokesman said.

Mitsubishi, already in labor with the system's second generation, will start offering a four-wheel steering, four-wheel drive, four-wheel independent suspension car to Japanese customers in October, 1988. "But as far as the U.S. market is concerned, that (4WS sales) is on hold," a representative said.

Chrysler is studying four-wheel steering but has no production plans. General Motors has examined about 15 systems, has shortlisted three, but is producing none.

'Not Convinced'

Ford has examined the concept, a company spokesman said, "but we're not convinced we need to shove it into a Taurus just yet. A decade ago we'd jump into anything the competition came up with. But five years ago we started working way ahead, taking everything a little slower and a little easier."

"We're definitely approaching it with caution," said Douglas Smith, former director of GM's four-wheel steering program. "Because it's another control system and that gets into the product-liability area. I think it (4WS) is going to happen. But I don't think it's going to be on every car nor will it be as widespread as the automatic (anti-lock) braking system."

Despite its apparent novelty, four-wheel steering is as old as an all-terrain-but-mostly-mountainside vehicle that Mercedes built for the German military in 1935. A British race car experimented with the system in the '50s. And hook-and-ladder fire trucks--albeit aided by a tail-end driver and a second steering wheel--have been effectively demonstrating four-wheel steering since the Great Chicago Fire.

The problem with two-wheel steering is this: when a conventional car's front wheels turn, a lateral force is generated at the front end, a yawing motion is created around the vehicle's center of gravity, the fixed rear wheels are dragged around with the rest of the car and there's a belated addition to the generation of lateral force. Plus the vehicle changes direction.

All of which makes for slower, wider turns with an uncomfortable, even dangerous shift of the balance of the moving vehicle when abruptly handled at higher speeds. That's what makes cars spin into the boonies or go wheels up in the middle of the Harbor Freeway.

With four-wheel steering, when the rear wheels move in the same direction as the front wheels, the development of lateral force is simultaneous, yaw is reduced, and the car responds quicker to the turn. You can make a U-turn a u-turn.

The means: Honda has gone basic with a purely mechanical system. The standard rack-and-pinion steering unit is mated by a drive shaft coupled to a set of planetary gears housed at the rear. Turning the steering wheel moves the front wheels; the eccentric drive shaft turns the planetary gears that move tie rods turning the rear wheels.

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