zimmthumps
Full Member
Four-Wheel Steering Makes Pickups More Maneuverable
ORLANDO, Fla. -- It's no argument: The most popular vehicle in America is the pickup truck. The perennial top seller is the Ford F-150, followed by the Chevrolet Silverado. But driving trucks has drawbacks, not the least of which the fact that they are long, and not particularly maneuverable.
New technology is changing that, and like a lot of new technology, it's expensive. But how much would it be worth to you to make an extended-cab pickup, with an overall length of 227.7 inches, turn in the same space required by Saturn sedan, which is 178.1 inches long?
That's exactly what Quadrasteer does for the GMC Sierra Denali pickup. The 2002 Denali, probably the most deluxe pickup truck available, sells for $44,105, and right now, it's the only one with Quadrasteer. That will change for 2003. More on that in a moment.
Quadrasteer revives an idea that Honda and a few other manufacturers tried, and failed, to popularize in the late 1980s, and early 1990s: Four-wheel steering, meaning that the rear wheels steer just like the front wheels do. If you are turning left, for instance, the rear wheels turn just slightly to the right, to swing the rear end around the corner.
But when Honda introduced four-wheel steering on the 1988 Honda Prelude, the difference was not dramatic. The Prelude was already a small, very good-handling car, and while you could tell that the four-wheel steering was working, tests suggested that it did not improve lap times on a race track over a regular Prelude.
And since the Prelude was no problem to park anyway, the extra cost and complexity just wasn't worth it. Honda dropped the four-wheel steering option in 1994, and few noticed. Various forms of four-wheel steering came and went with other manufacturers, such as Nissan, Mazda and Mitsubishi, with even less impact.
Enter Delphi, a technology company that used to be a part of General Motors, but was spun off on its own, retaining GM as its largest customer. Delphi figured that four-wheel steering was a good idea for trucks, not cars.
On the Sierra Denali, four-wheel steering reduces the turning circle (the diameter of a circle made when a vehicle is turning with the steering wheel all the way to one side) by 21 percent, down to just over 37 feet. That's the same as the smallest Saturn.
And it's a very noticeable difference. Make a sharp right turn at an intersection from a narrow road, and the rear wheel doesn't jump over the curb. Parallel park, and the Denali feels like it's a much shorter vehicle.
But the biggest difference is in towing a trailer. At the introduction of Quadrasteer technology at an event in Detroit, GMC laid out a very tight course in a big parking lot, lining the course with pylons. Journalists had the chance to drive the course with the Quadrasteer on, and with it off (a dashboard-mounted switch allows you to turn the feature off if you want).
With the Quadrasteer off, everyone who drove the course took out several of the plastic pylons. With Quadrasteer on, navigating the course was no problem, even for those who had never towed a trailer before. It was a pretty convincing demonstration.
"The impact that four-wheel steering has is enormous," said Sam Mancuso, GMC Sierra bran manager. "It changes the entire driving dynamics."
It's a fairly simple system to understand, but an exceptionally complex system to design. The front wheels use regular hydraulic power steering, but the rear wheels steer using a big electric motor, one at each wheel. Delphi could use regular steering, but the electric motors can operate much faster than hydraulics. With hydraulics, there would be a delay from the time you turn the steering wheel to the time the rear wheels get the message.
At very low speeds, the rear wheels steer in the opposite direction as the front wheels, swinging the rear around like the rear driver on a hook-and-ladder fire truck. At higher speeds, the rear wheels steer in the same direction as the front wheels, aiding lane changes.
All this rear steering is not nearly as severe as the front steering -- when you are stopped, and you turn the steering wheel from side to side, you can see the rear wheels steer slightly, never more than a 12-degree angle, far less than the front wheels can turn. But it doesn't take much to make a difference in the handling.
The downside: Extra weight, cost and complexity. The rear fenders of the Denali are flared out slightly, to help make room for the wheels to steer. But otherwise, this is what is called "transparent technology" -- stuff that works, and works well, but otherwise calls no attention to itself.
For 2003, GMC and Chevrolet are making Quadrasteer available on less expensive extended cab and some crew cab pickups, and even the heavy-duty version of the Suburban SUV. Price has not been announced, but a good guess would be about $4,500 extra, which also includes many other features, such as the Denali's big 6.0-liter V-8 engine.
Is it worth it? If you need a big truck to tow trailers often, or if you have to negotiate tight roads and parking lots, yes. It's a genuine breakthrough.
ORLANDO, Fla. -- It's no argument: The most popular vehicle in America is the pickup truck. The perennial top seller is the Ford F-150, followed by the Chevrolet Silverado. But driving trucks has drawbacks, not the least of which the fact that they are long, and not particularly maneuverable.
New technology is changing that, and like a lot of new technology, it's expensive. But how much would it be worth to you to make an extended-cab pickup, with an overall length of 227.7 inches, turn in the same space required by Saturn sedan, which is 178.1 inches long?
That's exactly what Quadrasteer does for the GMC Sierra Denali pickup. The 2002 Denali, probably the most deluxe pickup truck available, sells for $44,105, and right now, it's the only one with Quadrasteer. That will change for 2003. More on that in a moment.
Quadrasteer revives an idea that Honda and a few other manufacturers tried, and failed, to popularize in the late 1980s, and early 1990s: Four-wheel steering, meaning that the rear wheels steer just like the front wheels do. If you are turning left, for instance, the rear wheels turn just slightly to the right, to swing the rear end around the corner.
But when Honda introduced four-wheel steering on the 1988 Honda Prelude, the difference was not dramatic. The Prelude was already a small, very good-handling car, and while you could tell that the four-wheel steering was working, tests suggested that it did not improve lap times on a race track over a regular Prelude.
And since the Prelude was no problem to park anyway, the extra cost and complexity just wasn't worth it. Honda dropped the four-wheel steering option in 1994, and few noticed. Various forms of four-wheel steering came and went with other manufacturers, such as Nissan, Mazda and Mitsubishi, with even less impact.
Enter Delphi, a technology company that used to be a part of General Motors, but was spun off on its own, retaining GM as its largest customer. Delphi figured that four-wheel steering was a good idea for trucks, not cars.
On the Sierra Denali, four-wheel steering reduces the turning circle (the diameter of a circle made when a vehicle is turning with the steering wheel all the way to one side) by 21 percent, down to just over 37 feet. That's the same as the smallest Saturn.
And it's a very noticeable difference. Make a sharp right turn at an intersection from a narrow road, and the rear wheel doesn't jump over the curb. Parallel park, and the Denali feels like it's a much shorter vehicle.
But the biggest difference is in towing a trailer. At the introduction of Quadrasteer technology at an event in Detroit, GMC laid out a very tight course in a big parking lot, lining the course with pylons. Journalists had the chance to drive the course with the Quadrasteer on, and with it off (a dashboard-mounted switch allows you to turn the feature off if you want).
With the Quadrasteer off, everyone who drove the course took out several of the plastic pylons. With Quadrasteer on, navigating the course was no problem, even for those who had never towed a trailer before. It was a pretty convincing demonstration.
"The impact that four-wheel steering has is enormous," said Sam Mancuso, GMC Sierra bran manager. "It changes the entire driving dynamics."
It's a fairly simple system to understand, but an exceptionally complex system to design. The front wheels use regular hydraulic power steering, but the rear wheels steer using a big electric motor, one at each wheel. Delphi could use regular steering, but the electric motors can operate much faster than hydraulics. With hydraulics, there would be a delay from the time you turn the steering wheel to the time the rear wheels get the message.
At very low speeds, the rear wheels steer in the opposite direction as the front wheels, swinging the rear around like the rear driver on a hook-and-ladder fire truck. At higher speeds, the rear wheels steer in the same direction as the front wheels, aiding lane changes.
All this rear steering is not nearly as severe as the front steering -- when you are stopped, and you turn the steering wheel from side to side, you can see the rear wheels steer slightly, never more than a 12-degree angle, far less than the front wheels can turn. But it doesn't take much to make a difference in the handling.
The downside: Extra weight, cost and complexity. The rear fenders of the Denali are flared out slightly, to help make room for the wheels to steer. But otherwise, this is what is called "transparent technology" -- stuff that works, and works well, but otherwise calls no attention to itself.
For 2003, GMC and Chevrolet are making Quadrasteer available on less expensive extended cab and some crew cab pickups, and even the heavy-duty version of the Suburban SUV. Price has not been announced, but a good guess would be about $4,500 extra, which also includes many other features, such as the Denali's big 6.0-liter V-8 engine.
Is it worth it? If you need a big truck to tow trailers often, or if you have to negotiate tight roads and parking lots, yes. It's a genuine breakthrough.
