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Comment by whelp_24 | Hacker News Reader

why do steer by wire at all? Is it cheaper somehow?

It means where you put the steering wheel doesn't have to have a firewall penetration and mechanical linkage through to the engines. That's a lot of mechanical joints which need to be continuous, and need greasing, sealing and have limits on relative angles between them that you don't need - as well as they have to have enough strength to transmit the forces involved.

By contrast, with steer-by-wire your system is essentially a black box you bolt on somewhere and then a more compact set of motors which can be coupled to the wheels at whatever is mechanically optimal.

The main reason not to do it is because your control systems need to be perfect. Conversely, above a certain vehicle mass, it's also not realistic to think that a human would be able to control the car anyway if the power steering failed, or that control system failures would still be devastating (i.e. if the power steering starts fighting you, you're going to lose).

Big rigs used to not have power steering, i think with adrenaline you'll be able to steer. I do concede that the power steering fighting you would be bad

I just want feedback from the road, wires don't give me that

You can absolutely get feedback from steer-by-wire. Ask any racing sim enthusiast. Those racing sim wheels can provide enough feedback to rip the wheel out of your hands.

That "feedback" doesn't meet my poorly framed hyperbole. I'm intimately familiar as a driver; both in sims and Real Fast Cars.

At what point does it go from feedback to lies? Some computer saying "yep, this is what's happening", if you're lucky.

I'll yield that has been the trend for eons. That said, I don't want more of it.

What lead to my first comment is the understanding that Tesla doing something where it's... different wires.

Bus vs Ethernet or whatever. It sounds even more muted/numb.

I don't want a real car to feel like a sim. It's getting harder to tell the difference for the wrong reasons.

It's not that the simulators are closing the gap, but that the cars are becoming simulators. Lowering standards is definitely one way to meet them.

Take your "we have feedback at home" and keep it

I'm half joking through most of this, by the way. The problem is there but I'm deliberately overstating it

It's important to keep in mind what the actual market for the vehicle is. It's not a sports car. Road feel is an anti-goal, it's undesirable in this market. Just like it's undesirable in the market for the Lexus - luxury SUVs. All you want here is some dynamic weighting for cornering loads and even then not that much of it.

Yea, that's fair. Antithetical, these 'boats' are likely well served by not feeling as much

I'd appreciate more feel in something basic like an Altima. Not even for remotely high performance situations

I can already hear the road, I might as well feel it /s

More importantly, how my tires are reacting to it. For something so underpowered they spin in the wet from a complete stop, something awful.

It's kind of nice to still be able to steer a car that is disabled and needs to be pushed around. Not always feasible depending on the disability, of course.

Yes, tow trucks are great, but sometimes it's handy to push a car out of the way while waiting for a tow.

Allows you to vary the steering ratio dynamically (how many "turns" lock to lock). Means a lot less arm twiddling during lower speed maneuvers, and can gradually increase the ratio as speed increases. Traditional mechanically linked steering racks (electric or hydraulic) don't do this and are the same number of turns lock to lock regardless of speed - they can only dynamically vary the amount of power assist, not the ratio. It's been something car manufacturers have wanted to do for a while.

Another benefit in theory is packaging - you can free up more space for cabin, front trunk or motors etc when you don't have to route a physical steering column.

You also don't need a collapsible steering column, as there is no steering column.

BMW had this on mechanically linked system for 20 years. It's called "Active Steering" in their marketing speak.

It's not really the same at all in practice though. With steer by wire you can get the lock to lock literally as little as you like - 150 degrees at low speed lock to lock in the Lexus system for example. In theory it could go from one extreme to the other in a single degree, its just software, although obviously no one sane would implement this. Active Steering on BMWs doesn't get remotely close to 150 degree low speed lock to lock.

It's a system that changes the ratio of the steering wheel rotation to the wheel angle dynamically while still mechanically linking the wheels to the steering wheel. It does not have the same parameters as Lexus system but many other things differ between BMWs and Lexuses too.

I’ve been driving a BMW with the variable ratio steering rack for over 10 years. It’s great. But it’s only variable ratio, not a dynamic ratio. Don’t confuse the two.

A variable ratio is just a regular rack and pinion setup, except the teeth on the rack are more narrowly spaced at the centre. It’s pre-defined, fixed and static. 30 degrees of steering input will always result in the same movement of the front wheels. It’s mechanically fixed.

The Cybertruck is a truly dynamic steering ratio. 30 degrees of steering input will result in a different outcome depending on othe variables such as road speed.

Active Steering is dynamic. It's not in every BMW though, you can test if your car has it by turning the steering wheel when stopped: it should only require 2 turns between locks with AS.

It has rear wheel steering, so there would be a lot of linkage needed to do that mechanically. That said, GM has been doing rear wheel hydraulic steering for a couple decades and the front steering is still mechanical in those (at least historically, not sure if that has changed with their EV lineup).

Just about every car manufacture has done rear steer at some point I believe. Nissan had it done initially with a Hydraulic system then electric.

Probably. I know Dodge and Mitsubishi have done it too.

Hmmm.. I would guess decoupling would allow variable ratio steering based on speed or preferences.

Electric power assist already allows that. It's probably cheaper, lighter and maybe safer to have no steering column.

They almost always only vary the amount of power assistance, not the ratio. The ratio is fixed on virtually all electrically power assisted steering racks ever shipped. There is still a fixed mechanical linkage - decoupling this is what allows the ratio to be dynamically adjusted. To date only a handful of Lexus production cars have had dynamic variable ratio and decoupled steering via drive by wire.

Electric power steering is essentially the same in use as traditional hydraulic systems - they just replace the hydraulic assistance with electric motors.

The big advantage of decoupling and steer by wire is dynamic variable ratio, as well as packaging - no steering column to worry about making space for.

and you could invert X :)

Nah, there are variable ratio mechanical systems. On a rack and pinion setup, for instance, you vary the spacing of the teeth on the rack. ZF's been doing this for decades.

Generally speaking almost all mechanical steering systems are not dynamic though, you are missing the point entirely. It can't change the spacing of the teeth on the fly - steer by wire effectively does. The number of turns lock to lock on a mechanical system is almost always the same, regardless of speed.

With steer by wire, you can easily implement say one turn lock to lock at low speed for easier parking, increasing to 2-3 turns at highway speeds for stability. Which is essentially exactly what the recent Lexus model with such a system does. At low speed it can turn its wheels from one extreme to the other in just 150 degrees of steering wheel rotation - no hand over hand turning etc. 150 degrees is essentially unthinkable on a mechanical rack and pinion system, as it would make the car incredibly twitchy on a highway.

> https://www.motortrend.com/reviews/2023-lexus-rz450e-steer-b...

  It can't change the spacing of the teeth on the fly.

Geez, Elon really ought to start a goalpost moving company. But hey I'll play: yes, yes it can. That's precisely what BMW's active steering is, yes it's mechanical, yes it varies the ratio depending on speed, and yes it's been around for a couple decades now.

BMW active steer doesn't get remotely close to 150 degrees lock to lock when maneuvering (minimum rotation reached is ~720 degrees/2 turns), or offer the infinite and instant range of adjustability you can get with a drive by wire system. But sure, it's just the same. I couldn't care less whether the system is on a Tesla or not, its just abundantly clear there are some design and packaging advantages when you lose the mechanical link in anything with a steering wheel.

The vast, vast majority of rack and pinion systems ever made, both old and modern, don't adjust number of turns lock to lock at all, whereas the ability to essentially infinitely adjust it is inherent in all drive by wire steering systems.

Before we change the goalposts again it's worth noting that Tesla (and to a lesser extent Lexus) make vehicles where the primary focus is on the gadgets and BMW's focus is on the driver interface.

  BMW active steer doesn't get remotely close to 150 degrees lock to
  lock when maneuvering

Well, no. Super fast steering ratios are not an advantage, they're a necessary evil with a square steering control. There's nothing inherent in the BMW design that would prevent such a fast ratio beyond the reputation for emulating analog interfaces with quite a bit of fidelity. It speaks more to the intended use (gadget vs car) than to the underlying technology itself.

  its just abundantly clear there are some design and packaging
  advantages when you lose the mechanical link in anything with
  a steering wheel.

Every time I see this I wonder if the commentor has seen a hydraulic power steering pump. They're tiny as hydraulic and pneumatic drives are often quite a bit smaller than comparable electric ones (e.g. cordless vs pneumatic power tools). The only clear advantage that electric steering offers is one of efficiency (as a result of not driving a hydraulic pump all of the time). The rest is largely a series of trade offs, especially if you look at recirculating ball / worm gear vs rack and pinion drives.

> Every time I see this I wonder if the commentor has seen a hydraulic power steering pump. They're tiny as hydraulic and pneumatic drives are often quite a bit smaller than comparable electric ones (e.g. cordless vs pneumatic power tools).

The pump or motor size is totally irrelevant to this discussion and to the packaging advantages.

There is no steering column with steer by wire. If you have seen a mechanical steering column, as found in all hydraulic and electric power steering systems, it requires a significant amount of space to route from cabin to the front wheels, and you are limited in the paths and angles it can take to reach the rack. This is completely gone in steer by wire - that's the packaging advantage - not the pump, not the motors.

Taken to the extreme, you can do designs that are completely impossible with mechanical steering columns - see the Canoo design for example, which uses steer by wire to create a cabin that would literally be impossible with a steering column:

https://www.canoo.com/canoo/

You could even design interiors that can switch from left hand to right hand drive, with a sliding steering wheel. It also reduces the cost of shipping left and right hand drive variants, as you no longer need to engineer space on both the left and right sides of the car to fit the column for different markets.

But no need to take only my word for it; ZF, as in your earlier examples, also make the exact same arguments about packaging (and also about infinite adjustability, fwiw):

> "SbW's (Steer by Wire) additional advantages include gaining space in general and new design options in the cockpit... There is now more legroom because there is no longer a steering structure running through it."

> "In terms of steering experiences – from sporty-direct to comfortable-relaxed – every setting is possible in the same car. The system can also translate the same steering wheel movement variably depending on the driving situation, i.e. for parking and at low city speeds, the wheels angle (very) strongly for the change of direction, while they angle only slightly at high highway speeds."

https://www.zf.com/mobile/en/technologies/vehicle_motion_con...

> "we can make the steering ratio completely variable depending on the driving situation – unlike the fixed steering ratios used for a mechanical connection between the steering wheel and the front wheels"

> "Installing steer-by-wire steering systems reduces the assembly effort needed to build today's right-and left-hand drive versions of the same passenger car model."

https://www.zf.com/mobile/en/technologies/vehicle_motion_con...

  If you have seen a mechanical steering column

I have in fact had to remove the column on one of my cars, mostly to deal with the attached electronics. It's a relatively small device with a couple of u-joints.

  see the Canoo design for example, which uses steer by wire to create a
  cabin that would literally be impossible with a steering column

See the first three generations of Volkswagen vans.

There is literally air between the steering wheel and the rest of the car in the Canoo, as well as significantly more front leg room - its nothing like the VW, which has an almighty big steering column between the drivers legs. Unless of course ZF and the rest of the car industry are also wrong about it taking less room to package and permitting new designs?

If you have seen a column - congratulations, you will then know it needs room to route to the wheels, and is restricted in the paths it can take to get there quite significantly, vs of course plain ole wires that can snake any way you like. Those restrictions are exactly why your VW vans have a column between the drivers legs.

This is getting genuinely funny now, however I think I'm about done with this one. Enjoy the rest of your day.

… have you not seen the inside of a Volkswagen (or any other rear/mid engine) van/bus?

Sure have!

Again, one mighty big steering column, present on the T2, T3, "the first three generations of Volkswagen vans" etc etc.

> https://www.cnet.com/a/img/resize/309b66cd757b35f8a47ba3d385...

Are you just ignoring the ZF articles now they don't fit your arguments anymore? Again - it's not just me saying this!

The Canoo - no column, and a ton of front cabin space:

> https://i.pinimg.com/originals/96/28/33/96283349b392b1da2f0f...

https://www.zf.com/mobile/en/technologies/vehicle_motion_con...

As far as I know there is no technological problem for BMW system to have whatever desired rate of adjustability and speed of reaction. It uses planetary gearset with adjuster motor connected to one of the gears - a bot similar to how Toyota Prius's transmission works. So it's more a question of how manufacturer decided it should feel for the user.

I meant decoupled variable ratio, not mechanical variable ratio[1], not power assist.

sort of like turning mouse acceleration on and off.

[1] https://en.wikipedia.org/wiki/Steering_ratio#Variable-ratio_...

No matter what we think about FSD, Tesla's end goal are robotaxis – eventually probably with no steering wheels. Steer by wire is a stepping stone in that direction.

Steer by wire is cheaper to produce, as it allows you to reduce costs for RHD markets (e.g. Australia, New Zealand, UK, Thailand, Indonesia, Japan, etc).

For example, Ford F-150 and RAM 1500 trucks from the US are exported to Australia where they need to undergo an expensive conversion process before they can be sold. This is why a base model F-150 is US$74000 in Australia.

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