All wheel steering vs front wheel steering

[SamtheLeo]

Hi Guys,

I am not sure if I am using the correctr technical language for the same, but I would like to know

1. How is All wheel steering different from normal Front wheel steering (if that what we call them, else please advise correct terminology). Which is better of the two
2. Do we have any cars/SUV which come in India with all wheel steering.
3. Is it possible to change a front wheel steering to all wheel if it is better.

[neel385]

Other than some Military vehicles and Concept cars, no other vehicle uses all wheel steering. In all wheel steering systems, the front and rear wheels are rotated in opposite directions to turn the vehicle. The OSA-AK SAM carrier used by the IAF and the Army uses this type of steering system.

Not really aware iof any vehicle which has the ability to go from all to to front wheel only!!

Changing the steering system is going to be a rather expensive proposition and that too if you can get someone who has the technical acumen to do it and anyway, why would you want to do it?

[SamtheLeo]

Originally Posted by neel385

Other than some Military vehicles and Concept cars, no other vehicle uses all wheel steering. In all wheel steering systems, the front and rear wheels are rotated in opposite directions to turn the vehicle. The OSA-AK SAM carrier used by the IAF and the Army uses this type of steering system.

Not really aware iof any vehicle which has the ability to go from all to to front wheel only!!

Changing the steering system is going to be a rather expensive proposition and that too if you can get someone who has the technical acumen to do it and anyway, why would you want to do it?

Thanks for reply Neel,

Thats exactly my question
Why an all wheel steering system been developed & what are its benefits. Does it really make an impact on driving???

[Thad E Ginathom]

Honda Prelude was a production car which did* use all-wheel steering; sorry, can't specify year or exact model, my guess is late 80s or 90s.

A Honda expert will be along....




*not in India, I guess.

[iceman91]

1989-1990 prelude has all wheel steering. one for sale on tbhp.
So do a few other cars

[SirAlec]

Originally Posted by neel385

In all wheel steering systems, the front and rear wheels are rotated in opposite directions to turn the vehicle.

I don't think he meant this. I have heard this type only in two vehicle;
one in some old oversize fire engines which needed two divers, one main and other skilled one at the back of the vehicle. Other being a concept by JEEp, which has two V8s one at the front and other at the back.

what he meant by is called active four wheel steering, which can be seen in many vehicle. BMWs, toyota, and mostly nissan.

[doomsday]

Originally Posted by iceman91

1989-1990 prelude has all wheel steering.
So do a few other cars

True. A surprising number of cars have used active 4WS at some point of time. AFAIK, the predecessor to the R32 GT-R, the Skyline GTS. It has been featured on all GT-Rs upto the R34, apart from the Silvias and 300ZX. Nissan calls the system HICAS (Hi Capacity Active Steering).

The 3000GT was another car known for the 4WS, it didn't help its 'weight problems' though which prevented it from becoming a threat to the Supra and the GTRs.

From Honda's stable, the Prelude (late-eighties) and the Accord (early nineties) came equipped with 4WS. It was just a trend in the vehicle dynamics approach, which died a natural death, given the fact that 4WS added more problems rather than solving them- 'funny' handling at limit when rear wheels add to the steering motion, the weight of the system etc. etc. given the fact that it was seen more on vehicles with sporty pretensions and these drawbacks were not acceptable.

However, the 4WS has made a comeback of sorts recently- appearing on the new BMW 7-Series in an attempt to improve its low-speed manouverability by pointing the rear wheels in the opposite direction at low speeds.

[Abbas]

Originally Posted by neel385

In all wheel steering systems, the front and rear wheels are rotated in opposite directions to turn the vehicle.

Monster trucks in the U.S. and trucks used in construction have this kind of steering system. Seen one Volvo truck in kolkatta long back. Its basically used to reduce turning radius. Generally found in large vehicles.

[Bailee_Jatt_Boy]

Most of the contruction trucks the giant ones have this system in them. They ones that I have mostly seen are the ones with 10 tyres the broad ones. A whole lot of them are kenworths I think the idea is to increase the handling of the trucks. the done necessarily change the direction of the rear tyres but actually turn the first three rows of tyres in the same direction. like the one in this picture where the first two rows of tyres would turn



All the monster trucks from the monster truck mania use this system. Look for any clip on you tube and you will see how it helps in enhanced handling.

As far as sedans are concerned I have no idea which ones use it. I would think it might be tough to implement this idea effectively in sedans for lack of proper space near rear wheels

[Gasolinejunkie]

Quite a few cars in the late 80s & early 90s had 4WS, I think Honda was the first to start the trend with the 2nd generation Accord and 1st Generation Prelude. And later Nissan had AWS or so they called it in the 300s, R32 & R33 Skyline. Even Mazda had it in the 626 if I’m not wrong.
This is active 4 wheel steering and different manufacturers had different ways of engineering it. Honda had a two steering racks and had speed sensitive steering for both the front & rear. Under 35kmph the rear wheels turned in the opposite direction as the fronts and over 35 they turned the same direction but only a fraction of the angle. Nissan had a bigger power steering pump and had hydraulic lines running to a second steering rack at the rear.
Passive 4 wheel steering is also something that is widely present and unheard of, Mitsubishi had it on their Magna’s and Varadas. This is when the fore lower control arm bushes flex to follow the path of the vehicle, I don’t know what other cars use this technology.

Eventually just like a lot of toys from the 80s 4WS died out because it was a waste of manufacturing cost for the amount of benefits it had. My friend had a 91 Prelude with 4WS and it was a pain to drive. He ended up wrapping it around a tree while taking a corner, and always blamed it on the 4WS but I know it was alcohol!

[Guna]

I had read about 4 wheel sterring way back in 92 but still this doent seem to have made it to mainstream.

This is how the particular version worked as per the article:

In slow speeds, when you turn the steering to left, the front wheels would trun to the left as usual but the rear wheels turn to the right. This will enable very tight turning radius as the center of the turning circle is very close to the car.

As the speed increaes, the degree to which the rear wheel truns is reduced and at one point it becomes null.

Beyond this speed, the rear wheels start turning in the same direction as front but to a lesser degree.

[kaynmantis]

Im no expert here, but I believe 4WS are designed for different purpose. One is to have tight turning radius or make turning possible in normal roads in case of long vehicles. However Cars like the Nissan R34 GT, the 4WS is to counter the understeer that are inherent of AWD 4WD systems.

[SamtheLeo]

Thanks a lot guys, for the knowledge however would this All wheel Steering help in Offroading in any way? Can the driver control which wheels to trun & how much.

Also if we talk about tight turning radius do we have this in F1

[kaynmantis]

Originally Posted by SamtheLeo

Thanks a lot guys, for the knowledge however would this All wheel Steering help in Offroading in any way? Can the driver control which wheels to trun & how much.

Theoratically yes, it may help in offroading if the rear wheels are capable of turning its wheels like the front. This may allow drivers a greater degree to navigate through obstacles. However note, 4WS in performance cars are not meant for tight turning radius, rather they are used for countering under steer or for better traction control. In cars such as the r34, the rear wheel turning controls are automatic and for that matter they only turn a tiny fraction in relation to the front wheels.

The only Rear wheel steering where driver can control the rear wheel I know is an extraordinary long fire truck in the US where there is a second driver at the rear to steer the rear wheels.

Also if we talk about tight turning radius do we have this in F1

No. There is no F1 track where turns are tight enough to warrant a 4WS. Even if its to be used for better traction, the extra weight for such a technology would nullify its purpose.

[neel385]

Originally Posted by SirAlec

I don't think he meant this. I have heard this type only in two vehicle;
one in some old oversize fire engines which needed two divers, one main and other skilled one at the back of the vehicle. Other being a concept by JEEp, which has two V8s one at the front and other at the back.

what he meant by is called active four wheel steering, which can be seen in many vehicle. BMWs, toyota, and mostly nissan.

Actually I exactly meant what i wrote....I think you might be confusing all wheel drive cars with all wheel steering systems. The vehicle I was talking about, the OSA AK carrier, has three pairs of wheels and the front and rear pairs move in opposite directions to turn the vehicle this allowing it to do a spot turn....the same concept was used in the Honda being talked about to ease parking problems in cramped spaces.