Modern electric power steering
Discussion
Am I the only one thinking about building a slower rack for my modern? I have a number of cars, & find the old ones, with much slower racks more drivable at high speed.
I used to tune the suspension & steering of other peoples racing cars back in the day when I was racing F1 & F2 cars.
Many had a dreadful rack produced by Lynx engineering, which had go-kart directness. It was impossible to drive quickly around fast corners as you only had to blink to turn hard right or left. For high speed cornering you need to be able to adjust the angle of your front road wheels by a degree or so at times, to maintain car balance.
I had quite a few fit much slower racks to their open wheelers, & with no other modification, all bar one reduced their lap times by a couple of seconds at places like Warwick Farm, with 1M 30S lap times.
I have a number of cars, & find the Honda S2000 is a great car, badly spoiled by it's too light, too direct steering. Changing the weight on it would be totally useless, as it is so ridiculously direct that it is again go kart like, & actually dangerous at really high speed. I believe this is why so many of these cars die at places like Newberg ring. They are too hard to balance when fine changes of road wheel angles are almost impossible to make.
I wondered if I was just out of date, so made a point of watching the F1s through the hairpin at Monaco, where the photography allows it. Just as in my day, every single car required full crossed arms, plus a little bit more to get round it.
My Honda would require no more than 20 degrees of steering wheel turn to get around the same corner. These, & most modern cars are now dangerous at really high speeds, as they are totally compromised to suburban right angle cornering. Perhaps it is a good thing that speed limits have become ridiculously low. It is all that is saving so many in their shopping trolleys.
I used to tune the suspension & steering of other peoples racing cars back in the day when I was racing F1 & F2 cars.
Many had a dreadful rack produced by Lynx engineering, which had go-kart directness. It was impossible to drive quickly around fast corners as you only had to blink to turn hard right or left. For high speed cornering you need to be able to adjust the angle of your front road wheels by a degree or so at times, to maintain car balance.
I had quite a few fit much slower racks to their open wheelers, & with no other modification, all bar one reduced their lap times by a couple of seconds at places like Warwick Farm, with 1M 30S lap times.
I have a number of cars, & find the Honda S2000 is a great car, badly spoiled by it's too light, too direct steering. Changing the weight on it would be totally useless, as it is so ridiculously direct that it is again go kart like, & actually dangerous at really high speed. I believe this is why so many of these cars die at places like Newberg ring. They are too hard to balance when fine changes of road wheel angles are almost impossible to make.
I wondered if I was just out of date, so made a point of watching the F1s through the hairpin at Monaco, where the photography allows it. Just as in my day, every single car required full crossed arms, plus a little bit more to get round it.
My Honda would require no more than 20 degrees of steering wheel turn to get around the same corner. These, & most modern cars are now dangerous at really high speeds, as they are totally compromised to suburban right angle cornering. Perhaps it is a good thing that speed limits have become ridiculously low. It is all that is saving so many in their shopping trolleys.
Three things spring to mind here:
1) Suspension Setup/Geometry: I'm no expert on this, but I suspect much of the directness that you mention in modern cars is down to suspension geometry, rather than steering ratio. The most stable and calm cars at speed that I've driven have often had relatively quick racks - Caterhams, Lotuses and even single seaters, whereas most of the cars that I've driven that are darty at speed have been quite mundane modern hatchbacks and saloons (most modern Alfas for example and also many Vauxhalls), with sporty pretences. Many modern cars have this deliberately non linear response to make them feel sporty (i.e. super responsive), with mild control use for the average driver - i.e. small steering angles, or small throttle or brake pedal movement. My wife's Civic Type R is so jumpy and darty to initial control movement that it's really very distracting - it's probably the only thing I dislike about the car. True sports cars and racing cars generally don't have this, and thus feel much calmer, although the response is there if you want it, it's just that the controls are linear and calmer.
2) Centre of Gravity Location: The other thing worth considering is the height of the CofG and the springs and dampers. It's the fashion now for cars to have quite high centre of gravity, which can a) make any steering movements seem greater because of how high you sit and how far you move for any given roll angle of the car (like being in a crow's nest rather than on the deck of a ship) and b) This high CofG will cause greater instability for a given amount of roll.
3) Steering Input Force vs Angle Lastly, it's often not steering wheel input angle that is the problem with high speed instability, it's steering wheel input force. The fact that a single seater only has just over 1 turn lock to lock is usually entirely negated by the fact that the steering's very heavy, whereas a hatchback with ePAS designed for dry steering in a town centre car park would have really light steering. Put the same force into both cars' steering wheels with your hands and guess which one responds with more steering angle at the wheels! This effect would probably totally negate any difference in steering ratio.
Combine the three points above and you get quite a nasty recipe. I really hate most modern road cars!!
1) Suspension Setup/Geometry: I'm no expert on this, but I suspect much of the directness that you mention in modern cars is down to suspension geometry, rather than steering ratio. The most stable and calm cars at speed that I've driven have often had relatively quick racks - Caterhams, Lotuses and even single seaters, whereas most of the cars that I've driven that are darty at speed have been quite mundane modern hatchbacks and saloons (most modern Alfas for example and also many Vauxhalls), with sporty pretences. Many modern cars have this deliberately non linear response to make them feel sporty (i.e. super responsive), with mild control use for the average driver - i.e. small steering angles, or small throttle or brake pedal movement. My wife's Civic Type R is so jumpy and darty to initial control movement that it's really very distracting - it's probably the only thing I dislike about the car. True sports cars and racing cars generally don't have this, and thus feel much calmer, although the response is there if you want it, it's just that the controls are linear and calmer.
2) Centre of Gravity Location: The other thing worth considering is the height of the CofG and the springs and dampers. It's the fashion now for cars to have quite high centre of gravity, which can a) make any steering movements seem greater because of how high you sit and how far you move for any given roll angle of the car (like being in a crow's nest rather than on the deck of a ship) and b) This high CofG will cause greater instability for a given amount of roll.
3) Steering Input Force vs Angle Lastly, it's often not steering wheel input angle that is the problem with high speed instability, it's steering wheel input force. The fact that a single seater only has just over 1 turn lock to lock is usually entirely negated by the fact that the steering's very heavy, whereas a hatchback with ePAS designed for dry steering in a town centre car park would have really light steering. Put the same force into both cars' steering wheels with your hands and guess which one responds with more steering angle at the wheels! This effect would probably totally negate any difference in steering ratio.
Combine the three points above and you get quite a nasty recipe. I really hate most modern road cars!!
Edited by RobM77 on Thursday 12th February 15:46
RobM77 said:
I'm no expert on this, but I suspect much of the directness that you mention in modern cars is down to suspension geometry, rather than steering ratio. The most stable and calm cars at speed that I've driven have often had relatively quick racks - Caterhams, Lotuses and even single seaters, whereas most of the cars that I've driven that are darty at speed have been quite mundane modern hatchbacks and saloons (most modern Alfas for example and also many Vauxhalls), with sporty pretences. Many modern cars have this deliberately non linear response to make them feel sporty (i.e. super responsive), with mild control use for the average driver - i.e. small steering angles, or small throttle or brake pedal movement. My wife's Civic Type R is so jumpy and darty to initial control movement that it's really very distracting - it's probably the only thing I dislike about the car. True sports cars and racing cars generally don't have this, and thus feel much calmer, although the response is there if you want it, it's just that the controls are linear and calmer.
I can't help the OP but that's an interesting post RobM77, thanks. Oli.
RobM77 said:
1) Suspension Setup/Geometry: I'm no expert on this, but I suspect much of the directness that you mention in modern cars is down to suspension geometry, rather than steering ratio.
You only need to look at the ratio's of some of the new EPS equipped cars to see that it's predominately rack ratio with EPS.The new EPS steering in the F** series BMW's is now down to only 2 turns lock to lock, and it's horrible. Blimey, back in the day, the works spec 'quick' racks on BDA Escorts and Sunbeams etc was only 2.2 turns, so yes, I'd agree with the OP, too fast a ratio combined with zero feel makes for rubbish steering in most of these modern EPS cars.
aeropilot said:
RobM77 said:
1) Suspension Setup/Geometry: I'm no expert on this, but I suspect much of the directness that you mention in modern cars is down to suspension geometry, rather than steering ratio.
You only need to look at the ratio's of some of the new EPS equipped cars to see that it's predominately rack ratio with EPS.The new EPS steering in the F** series BMW's is now down to only 2 turns lock to lock, and it's horrible. Blimey, back in the day, the works spec 'quick' racks on BDA Escorts and Sunbeams etc was only 2.2 turns, so yes, I'd agree with the OP, too fast a ratio combined with zero feel makes for rubbish steering in most of these modern EPS cars.
source: http://blog.caranddriver.com/a-tale-of-two-bmw-3-s...
The big difference is the rate that lateral loads can build up on modern cars with extremely low profile tyres, and extremely "laterally stiff" suspension systems. Ie, you turn the handwheel by 15 degrees, the front wheels turn by 1degree, which on an old car with tall sidewalls and rubbery suspension would just result in a load of deflection in those parts, and very little lateral load and hence little yaw. With a modern, 1deg of steering road wheel leads to a MASSIVE and immediate yaw build up. This makes them actually easier to drive, once you have learnt to tame your inputs, because this lack of delay also means the phase delay is minimised, and that non linearity is what used to catch a lot of drivers out.
The real reason people crash there moderns is that they have no idea how to drive, have never ever got close to the limits of the car under controlled conditions, have never been taught to "feel" for the grip available, and hence, when a car pulls out on them, they just yank on half a turn of handwheel and the car promptly just driver clean off the road!
In reality, though, i've not driven a modern car that i would call "dangerous" at high speed. Frankly, with modern chassis, and the additional safety net of electronic stability control, you have got to be an epic numpty to loose control of one (of course, people do.........)
The real reason people crash there moderns is that they have no idea how to drive, have never ever got close to the limits of the car under controlled conditions, have never been taught to "feel" for the grip available, and hence, when a car pulls out on them, they just yank on half a turn of handwheel and the car promptly just driver clean off the road!
In reality, though, i've not driven a modern car that i would call "dangerous" at high speed. Frankly, with modern chassis, and the additional safety net of electronic stability control, you have got to be an epic numpty to loose control of one (of course, people do.........)
Max_Torque said:
The big difference is the rate that lateral loads can build up on modern cars with extremely low profile tyres, and extremely "laterally stiff" suspension systems. Ie, you turn the handwheel by 15 degrees, the front wheels turn by 1degree, which on an old car with tall sidewalls and rubbery suspension would just result in a load of deflection in those parts, and very little lateral load and hence little yaw. With a modern, 1deg of steering road wheel leads to a MASSIVE and immediate yaw build up. This makes them actually easier to drive, once you have learnt to tame your inputs, because this lack of delay also means the phase delay is minimised, and that non linearity is what used to catch a lot of drivers out.
The real reason people crash there moderns is that they have no idea how to drive, have never ever got close to the limits of the car under controlled conditions, have never been taught to "feel" for the grip available, and hence, when a car pulls out on them, they just yank on half a turn of handwheel and the car promptly just driver clean off the road!
In reality, though, i've not driven a modern car that i would call "dangerous" at high speed. Frankly, with modern chassis, and the additional safety net of electronic stability control, you have got to be an epic numpty to loose control of one (of course, people do.........)
Whilst that's true (although see below), the effects that I describe above certainly exist. Vauxhall and Alfa, as mentioned, make cars that have a lot of initial steering response, which then fades into woolly understeer as lateral force builds up. I suspect it might be the toe values changing throughout suspension deflection? (by design). It's a very noticeable trait. My wife's CTR also, as mentioned above, is like a hyperactive rabbit in the initial movement of steering, throttle and brake, but once that initial period's over is perfectly linear like the standard Civic - I find it genuinely hard to drive because of it. The throttle is obviously just a 'sport' throttle mapping, and the brakes are over-served to give the superficial feeling of power (as most modern cars are), but the steering does it too...The real reason people crash there moderns is that they have no idea how to drive, have never ever got close to the limits of the car under controlled conditions, have never been taught to "feel" for the grip available, and hence, when a car pulls out on them, they just yank on half a turn of handwheel and the car promptly just driver clean off the road!
In reality, though, i've not driven a modern car that i would call "dangerous" at high speed. Frankly, with modern chassis, and the additional safety net of electronic stability control, you have got to be an epic numpty to loose control of one (of course, people do.........)
Whilst I wouldn't describe modern cars as dangerous, I wouldn't want to have to avoid anything in one. I had a Peugeot 208 the other day as a courtesy car and if you wiggled the steering left and right at 30mph on a wide empty straight road there was such a delay in response that after a few seconds to allow the effect to build, you were steering right whilst the car was moving left! You could also turn the wheel one way in isolation and then wait a noticeable period before the front end responded. The stability at high speed feels shocking as well in most modern cars - in a mk1 Corsa for example you could swerve to avoid something at 60mph (not that I'd recommend that, but that's another discussion entirely) - in the latest Corsa the dam thing's so high up I reckon you'd get into serious trouble if you tried a similar manoeuvre because the car's mass is rolling around all over the place.
RobM77 said:
Whilst that's true (although see below), the effects that I describe above certainly exist. Vauxhall and Alfa, as mentioned, make cars that have a lot of initial steering response, which then fades into woolly understeer as lateral force builds up. I suspect it might be the toe values changing throughout suspension deflection? (by design). It's a very noticeable trait. My wife's CTR also, as mentioned above, is like a hyperactive rabbit in the initial movement of steering, throttle and brake, but once that initial period's over is perfectly linear like the standard Civic - I find it genuinely hard to drive because of it. The throttle is obviously just a 'sport' throttle mapping, and the brakes are over-served to give the superficial feeling of power (as most modern cars are), but the steering does it too...
Whilst I wouldn't describe modern cars as dangerous, I wouldn't want to have to avoid anything in one. I had a Peugeot 208 the other day as a courtesy car and if you wiggled the steering left and right at 30mph on a wide empty straight road there was such a delay in response that after a few seconds to allow the effect to build, you were steering right whilst the car was moving left! You could also turn the wheel one way in isolation and then wait a noticeable period before the front end responded. The stability at high speed feels shocking as well in most modern cars - in a mk1 Corsa for example you could swerve to avoid something at 60mph (not that I'd recommend that, but that's another discussion entirely) - in the latest Corsa the dam thing's so high up I reckon you'd get into serious trouble if you tried a similar manoeuvre because the car's mass is rolling around all over the place.
Most of a cars "steering" response actually comes from the rear suspension......... And yes, some manufacturers do build in a reduction in rear toe as lateral forces build to make the car seem "eager" and yet still have ultimate stability.Whilst I wouldn't describe modern cars as dangerous, I wouldn't want to have to avoid anything in one. I had a Peugeot 208 the other day as a courtesy car and if you wiggled the steering left and right at 30mph on a wide empty straight road there was such a delay in response that after a few seconds to allow the effect to build, you were steering right whilst the car was moving left! You could also turn the wheel one way in isolation and then wait a noticeable period before the front end responded. The stability at high speed feels shocking as well in most modern cars - in a mk1 Corsa for example you could swerve to avoid something at 60mph (not that I'd recommend that, but that's another discussion entirely) - in the latest Corsa the dam thing's so high up I reckon you'd get into serious trouble if you tried a similar manoeuvre because the car's mass is rolling around all over the place.
I'm sorry, but, no way will a corsa "fall over"! If might feel like it, but modern cars are objectively at least 2 times better at "swerving around" things that old (>10 yo) ones!
Thanks, that's exactly the phenomenon I was trying to describe. I hate any sort of non-linearity like that.
I wasn't suggesting a modern car would actually fall over, but the fashion for high up cars feels very dangerous to me - I just don't feel that cars like that would be capable of any predictable and controllable emergency action if it should be required.
I wasn't suggesting a modern car would actually fall over, but the fashion for high up cars feels very dangerous to me - I just don't feel that cars like that would be capable of any predictable and controllable emergency action if it should be required.
Max_Torque said:
RobM77 said:
Whilst that's true (although see below), the effects that I describe above certainly exist. Vauxhall and Alfa, as mentioned, make cars that have a lot of initial steering response, which then fades into woolly understeer as lateral force builds up. I suspect it might be the toe values changing throughout suspension deflection? (by design). It's a very noticeable trait. My wife's CTR also, as mentioned above, is like a hyperactive rabbit in the initial movement of steering, throttle and brake, but once that initial period's over is perfectly linear like the standard Civic - I find it genuinely hard to drive because of it. The throttle is obviously just a 'sport' throttle mapping, and the brakes are over-served to give the superficial feeling of power (as most modern cars are), but the steering does it too...
Whilst I wouldn't describe modern cars as dangerous, I wouldn't want to have to avoid anything in one. I had a Peugeot 208 the other day as a courtesy car and if you wiggled the steering left and right at 30mph on a wide empty straight road there was such a delay in response that after a few seconds to allow the effect to build, you were steering right whilst the car was moving left! You could also turn the wheel one way in isolation and then wait a noticeable period before the front end responded. The stability at high speed feels shocking as well in most modern cars - in a mk1 Corsa for example you could swerve to avoid something at 60mph (not that I'd recommend that, but that's another discussion entirely) - in the latest Corsa the dam thing's so high up I reckon you'd get into serious trouble if you tried a similar manoeuvre because the car's mass is rolling around all over the place.
Most of a cars "steering" response actually comes from the rear suspension......... And yes, some manufacturers do build in a reduction in rear toe as lateral forces build to make the car seem "eager" and yet still have ultimate stability.Whilst I wouldn't describe modern cars as dangerous, I wouldn't want to have to avoid anything in one. I had a Peugeot 208 the other day as a courtesy car and if you wiggled the steering left and right at 30mph on a wide empty straight road there was such a delay in response that after a few seconds to allow the effect to build, you were steering right whilst the car was moving left! You could also turn the wheel one way in isolation and then wait a noticeable period before the front end responded. The stability at high speed feels shocking as well in most modern cars - in a mk1 Corsa for example you could swerve to avoid something at 60mph (not that I'd recommend that, but that's another discussion entirely) - in the latest Corsa the dam thing's so high up I reckon you'd get into serious trouble if you tried a similar manoeuvre because the car's mass is rolling around all over the place.
I'm sorry, but, no way will a corsa "fall over"! If might feel like it, but modern cars are objectively at least 2 times better at "swerving around" things that old (>10 yo) ones!
Firstly, 'turns lock to lock' is not the same as the steering ratio.
The S2000 has a 13.something:1 ratio, which is pretty darn fast. It is commonly blasted for it's pack of feel.
The RX8 has a very similar Showa EPS rack, but a significantly slower 16:1 ratio. Never heard any criticisms of the RX8 steering. The suspensions setups are very similar, so although it's doesn't rule the chassis out of the list of factors contributing to better steering feel, it certainly makes a good case for that longer steering ratio....
The S2000 has a 13.something:1 ratio, which is pretty darn fast. It is commonly blasted for it's pack of feel.
The RX8 has a very similar Showa EPS rack, but a significantly slower 16:1 ratio. Never heard any criticisms of the RX8 steering. The suspensions setups are very similar, so although it's doesn't rule the chassis out of the list of factors contributing to better steering feel, it certainly makes a good case for that longer steering ratio....
Kozy said:
Firstly, 'turns lock to lock' is not the same as the steering ratio.
Years ago a manufacturer sold a sporty version of one of their mundane models. The steering ratio of the sporty variant was the same as the standard variant, but in an attempt to convince people it was better they simply restricted the rack length, reducing the number of turns lock to lock.Debaser said:
Kozy said:
Firstly, 'turns lock to lock' is not the same as the steering ratio.
Years ago a manufacturer sold a sporty version of one of their mundane models. The steering ratio of the sporty variant was the same as the standard variant, but in an attempt to convince people it was better they simply restricted the rack length, reducing the number of turns lock to lock.(because the "extra" cog mean't the gear box stuck out under the nearside chassis leg, and required an additional rack stop to prevent the nearside front wheel from rubbing on it on full right lock....)
Debaser said:
Years ago a manufacturer sold a sporty version of one of their mundane models. The steering ratio of the sporty variant was the same as the standard variant, but in an attempt to convince people it was better they simply restricted the rack length, reducing the number of turns lock to lock.
so it was better then!Max_Torque said:
And if you drove a Peugeot 306 Gti-6, you had more lock turning left than you did turning right!!
(because the "extra" cog mean't the gear box stuck out under the nearside chassis leg, and required an additional rack stop to prevent the nearside front wheel from rubbing on it on full right lock....)
Yes, a friend had one and kept getting caught out in car parks!(because the "extra" cog mean't the gear box stuck out under the nearside chassis leg, and required an additional rack stop to prevent the nearside front wheel from rubbing on it on full right lock....)
Gassing Station | General Gassing | Top of Page | What's New | My Stuff