4-Wheel steering

firsttruck

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Will Quadrasteer have a second life for Extreme Towing and Handling & ** crab steer **
Quadrasteer, it was a travesty the way Delphi and GM dropped the ball on the greatest truck improvement ever invented. MrTruck tells the story of Quadrasteer. ZF has a rear steer project that may finish the job Quadrasteer started.
MrTruckTV
Sep 7, 2019

MrTruckTV wrote several articles about Quadrasteer, see this one: https://mrtruck.com/qstour1.htm had a website QuadrasteerClub.com, See Andre Smirnov's review of ZF rear steer:
ZF produces steering systems for cars, trucks & buses
Twice the steering power: ZF launches next generation AKC active rear axle steering system in volume production
Latest Generation AKC offers rear steering angle of up to ten degrees
Steer-by-wire" rear axle steering improves agility of longer electric vehicles
2020-Oct-14
https://press.zf.com/press/en/releases/release_20547.html
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alan auerbach

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I tried to find a video of this, but failed. Maybe the 3 point tractor turn has another name?

I kept getting videos about 3 point hitches on tractors...
Never heard "3-pt turn" ON A TRACTOR but sometimes "brake turn." Whatever it's called, the shorter the wheelbase the more effective the technique -- and wheelbase is short on tractors, long on the CT.
 
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Luke42

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Never heard "3-pt turn" but sometimes "brake turn." Whatever it's called, the shorter the wheelbase the more effective the technique -- and wheelbase is short on tractors, long on the CT.
As a licensed driver, you've likely performed a 3-point turn, even if you call it something else:
 

alan auerbach

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I tried to find a video of this, but failed. Maybe the 3 point tractor turn has another name?

I kept getting videos about 3 point hitches on tractors...
Be glad to explain.

Tractors have huge rears usually with aggressive tread, often with weights. That's what gives them the traction that their name comes from. The fronts are more car-size, and lightly loaded. So making a sharp turn, especially a 180, depends on those little fronts.

So most tractors have brakes on the rears only, and (except for the non-serious ones) have two side-by-side brake pedals, one for each rear, that can be linked (so pressing either pedal operates both brakes) or separated (so you press either one to brake on that side only). To make a tractor turn, you'd brake-lock the "inner" rear, which then serves as a pivot.

This differential braking works less effectively on relatively long vehicles like the CT and those lacking the extra traction in the rears, so I doubt I'd pay extra to have it. Even on my tractor I use it maybe once a year.
 

alan auerbach

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One poster above listed higher payload as one advantage of rear steer. I can't see that because fixed wheels are less delicate and therefore can carry more weight than movable ones. That's why your car's front end often needs service whereas the back end hardly ever does, and why the load-bearing wheels on forklifts are not the ones that steer.
 

Crissa

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Fixed are less delicate, but... that goes out the window with air shock suspension. I don't know how load limit is determined, but I'm told that control is a part of it, not just good ol' dumb stiffness.

-Crissa
 

firsttruck

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One poster above listed higher payload as one advantage of rear steer. I can't see that because fixed wheels are less delicate and therefore can carry more weight than movable ones. That's why your car's front end often needs service whereas the back end hardly ever does, and why the load-bearing wheels on forklifts are not the ones that steer.
The main truck example is GM Quadrasteer. If you ordered the Quadrasteer for GM Sierra/Chev Silverado the max payload & towing limits were higher than if you did not buy the option. Other options lowered the limits.
 

jhogan2424

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Fixed are less delicate, but... that goes out the window with air shock suspension. I don't know how load limit is determined, but I'm told that control is a part of it, not just good ol' dumb stiffness.

-Crissa
Yes this is correct. Max load rating has other factors involved such as trailer sway at X speed with X tongue weight etc. The 4WS can help correct trailer sway to a certain degree so that adds to the maximum.
 

firsttruck

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Yes this is correct. Max load rating has other factors involved such as trailer sway at X speed with X tongue weight etc. The 4WS can help correct trailer sway to a certain degree so that adds to the maximum.

Is 4WS really correcting sway? I think of it more as 4WS helps prevent sway from happening because the 4WS movement is easier for the trailer to follow without over shooting the path.
 

Crissa

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Is 4WS really correcting sway? I think of it more as 4WS helps prevent sway from happening because the 4WS movement is easier for the trailer to follow without over shooting the path.
There's threads from last year showing quadrasteer trucks doing evasive maneuvers.

-Crissa
 

ldjessee

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I want 4WS for towing, how much easier it is to back a trailer around, etc.

Offroading would be number two...

And making it easier to park in tight parking lots is a consideration as well.
 

kev12345

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ZF produces steering systems for cars, trucks & buses
Twice the steering power: ZF launches next generation AKC active rear axle steering system in volume production
Latest Generation AKC offers rear steering angle of up to ten degrees
Steer-by-wire" rear axle steering improves agility of longer electric vehicles
2020-Oct-14
https://press.zf.com/press/en/releases/release_20547.html
didn't realize rear wheel steering offered such a huge benefit to sway control. anyone who has ever been whipped around by their trailer would gladly pay extra for this safety feature. I know I would!
 

jcryer3

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A tight turning radius is extremely important. I do not care how they achieve it.
 

rr6013

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Rear Wheel Steering(RWS) didn’t see it coming. Useful? Sure. $2k useful - no.

The BIG utility gained by Jeep is it has 21’ turning radius(‘03 Rubicon). That changed my offroad experience compared to wrangling turnaround in tight places. SO YES. Cybertruck RWS with 21’ turning radius! Bring it.

Otherwise, why go to the trouble, expense and complication to implement RWS half-assed. Its a truck. It’ll have to be treated as a truck, instead of out turning the Jeeps.
 
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