Lexus RC F Speed sensing steering

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Sup.

So I was wondering about the speed sensing power steering. I am having trouble understanding how this system works in this car. I know it detects speed, but my question is the steering stiffness. I know Sport/Sport+ mode stiffens the steering, but I want to know for those who own this car: At higher speeds, is turning the wheel harder than turning it at low speeds? Or does it keep the same amount of stiffness no matter the speed? Thanks if anyone can answer!
 

Sulu

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Sup.

So I was wondering about the speed sensing power steering. I am having trouble understanding how this system works in this car. I know it detects speed, but my question is the steering stiffness. I know Sport/Sport+ mode stiffens the steering, but I want to know for those who own this car: At higher speeds, is turning the wheel harder than turning it at low speeds? Or does it keep the same amount of stiffness no matter the speed? Thanks if anyone can answer!
I do not know the details of how the speed-sensing power steering works on the RC F; I would assume that it works in a similar fashion to all other speed-sensitive power steering systems out there.

At slow speeds (and low momentum), there is maximum assist to the steering, making the steering feel (very) light. As speed increases, power assist gradually lessens, to a minimum assist (perhaps even no assist) at high speeds (and high momentum), so steering effort should theoretically feel heavier.

But despite the lessening power assist as speed increases, steering effort may not feel heavier because steering typically feels lighter as speed and momentum increase (if power assist remains constant).
 
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I do not know the details of how the speed-sensing power steering works on the RC F; I would assume that it works in a similar fashion to all other speed-sensitive power steering systems out there.

At slow speeds (and low momentum), there is maximum assist to the steering, making the steering feel (very) light. As speed increases, power assist gradually lessens, to a minimum assist (perhaps even no assist) at high speeds (and high momentum), so steering effort should theoretically feel heavier.

But despite the lessening power assist as speed increases, steering effort may not feel heavier because steering typically feels lighter as speed and momentum increase (if power assist remains constant).
Well, when driving a car without power steering at higher speeds, the wheel doesn't feel 'heavy', but it does require some effort to turn. Now I would assume that, keeping the same level of stiffness, the steeringl would feel very light at even high speeds. I would think this would destroy the whole idea of a speed sensing system, since it's supposed to get heavier at higher speeds.
 
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Ian Schmidt

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I don't know the details of the Lexus system, but I know in my LS the steering effort feels generally similar from 0 to 100+ MPH. The wheel never feels either heavy or light to turn, it's somewhere in between. I would guess in the RC it might be tuned differently, but maybe go test drive one and see for yourself?
 

suxeL

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Does anyone know if this has a ratio changer where at parking speeds the lock to lock turns was far less then when at highway speeds.
 
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I don't know the details of the Lexus system, but I know in my LS the steering effort feels generally similar from 0 to 100+ MPH. The wheel never feels either heavy or light to turn, it's somewhere in between. I would guess in the RC it might be tuned differently, but maybe go test drive one and see for yourself?
Actually, what year is your LS? The 2010 LS460 actually has VGRS steering, not vehicle-speed-sensing power steering. VGRS does detect speed, but it changes the gear ratios as your speed increases. And, as far as test drives, I'm too young to drive. I honestly just want to know a lot about these cars, since they are my favorite.
 

Sulu

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Well, when driving a car without power steering at higher speeds, the wheel doesn't feel 'heavy', but it does require some effort to turn. Now I would assume that, keeping the same level of stiffness, the steeringl would feel very light at even high speeds. I would think this would destroy the whole idea of a speed sensing system, since it's supposed to get heavier at higher speeds.
I am not sure what you mean by "stiffness"; I equate it with heaviness. If the steering wheel feels stiff to turn, it requires some heft to turn it and the steering feels heavy.

If there is only a little power assist (or no power assist) to the steering, the steering will feel quite heavy at low, parking lot speeds and feel lighter (less stiff) at highway speeds. This was the case with my 1987 Toyota Corolla, which had no power steering. The steering felt incredibly stiff and heavy at low, parking lot speeds (requiring quite a bit of heft to turn the steering wheel) and felt lighter (not terribly light but very controllable) at highway speeds.

If, however, there is a lot of power assist to the steering (in other words it is "over-boosted"), it will be light at parking lot speeds and feel incredibly light -- and twitchy -- at highway speeds. This was the case with my 2010 Toyota Corolla (the first generation of Corolla, if I remember correctly, to have electronic power assisted steering, rather than hydraulic power assist). The steering was light (but controllable) at low, parking lot speeds and fingertip-light -- and incredibly sensitive and twitchy -- at highway speeds.

Speed-sensitive power assisted steering was designed to reduce this lightness (and sensitivity) at high speeds while still offering light steering feel at low, parking lot speeds, by gradually reducing the level of power assist as speed increases. I suppose that this reduction of power assist can be tuned: Reduce a little and the steering feel remains light, even at high speeds (I could see luxury sedans such as the LS having variable-assist power steering with lower sensitivity to speed); reduce a lot and the steering feel is light at low speeds but becomes quite a bit heavier at high speeds (I could see sports cars such as the RC F having variable-assist power steering with higher sensitivity to speed).
 
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I am not sure what you mean by "stiffness"; I equate it with heaviness. If the steering wheel feels stiff to turn, it requires some heft to turn it and the steering feels heavy.

If there is only a little power assist (or no power assist) to the steering, the steering will feel quite heavy at low, parking lot speeds and feel lighter (less stiff) at highway speeds. This was the case with my 1987 Toyota Corolla, which had no power steering. The steering felt incredibly stiff and heavy at low, parking lot speeds (requiring quite a bit of heft to turn the steering wheel) and felt lighter (not terribly light but very controllable) at highway speeds.

If, however, there is a lot of power assist to the steering (in other words it is "over-boosted"), it will be light at parking lot speeds and feel incredibly light -- and twitchy -- at highway speeds. This was the case with my 2010 Toyota Corolla (the first generation of Corolla, if I remember correctly, to have electronic power assisted steering, rather than hydraulic power assist). The steering was light (but controllable) at low, parking lot speeds and fingertip-light -- and incredibly sensitive and twitchy -- at highway speeds.

Speed-sensitive power assisted steering was designed to reduce this lightness (and sensitivity) at high speeds while still offering light steering feel at low, parking lot speeds, by gradually reducing the level of power assist as speed increases. I suppose that this reduction of power assist can be tuned: Reduce a little and the steering feel remains light, even at high speeds (I could see luxury sedans such as the LS having variable-assist power steering with lower sensitivity to speed); reduce a lot and the steering feel is light at low speeds but becomes quite a bit heavier at high speeds (I could see sports cars such as the RC F having variable-assist power steering with higher sensitivity to speed).
Well, after reading a little more, it seems like the steering weight might change slightly at higher speeds (to be a little more stuff than at low speeds)
 
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