| Motoring Discussion > Steering angles | Miscellaneous |
| Thread Author: Number_Cruncher | Replies: 26 |
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New Sun 12 May 13 14:02
Steering angles - Number_Cruncher
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Prompted in another thread by a mention of the old nonsense of "asking front wheels to do too much", I've looked at some steering angles. What I've assumed is a neutral steering vehicle with a 2.5 metre wheelbase, going round a half g corner. For most normal driving, half g cornering is excessive - most driving rarely exceeds 0.4 g. The columns of figures are Speed (mph), from 10mph to 100 mph and the corresponding angle (degrees) the steered wheels must be rotated through. 10 : 35.1587 20 : 8.7897 30 : 3.9065 40 : 2.1974 50 : 1.4063 60 : 0.9766 70 : 0.7175 80 : 0.5494 90 : 0.4341 100 : 0.3516 It's notable that once you're doing more than 30 mph or so, the angle the steered wheels must rotate through is comparable with the slip angle, and for speeds above 60 or so, the angle is becoming very small. In one sense, this fits with our experience as drivers, once the vehicle is up to speed, only tiny inputs are usually required at the steering wheel. If a typical steering ratio is 12:1, steering wheel angles of more than 10 degrees at speeds of 60 mph and above are rare. When watching vehicles cornering at high speed, it's difficult to notice any steering angle at the road wheels themselves. This also goes some way to explain some high speed accidents - if a sudden high speed lane change is required, most drivers use much too much steering angle, and as you can see, will produce excessive lateral accelerations - or, in reality, produce a dangerous high speed skid. In reality, cornering force comes from all 4 wheels on a vehicle - in proportion to the front / rear weight distribution - not solely from the steered wheels. Last edited by: Number_Cruncher on Sun 12 May 13 at 14:06
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New Sun 12 May 13 14:10
Steering angles - Robin O'Reliant
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>> In reality, cornering force comes from all 4 wheels on a vehicle - in proportion >> to the front / rear weight distribution - not solely from the steered wheels. >> >> Interesting, similar to how a motorcycle steers perhaps? |
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New Sun 12 May 13 14:16
Steering angles - ToMoCo
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heh, just at lunch I was mulling over the very same thing. Came up with the same results. Well done. :-) |
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New Sun 12 May 13 14:21
Steering angles - Runfer D'Hills
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Yeah although to be fair, I'm impressed, I find it really hard to use a calculator when I'm hammering down a B road m'self...thing keeps sliding about on the passenger seat. :-) |
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New Sun 12 May 13 15:46
Steering angles - Robin O'Reliant
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Calculator, Humph? A bit of basic maths like that you should be able to do in your head. |
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New Sun 12 May 13 16:05
Steering angles - Runfer D'Hills
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Yes of course, naturally, but NC has rounded it up to only 4 decimal places so they're just estimates really. I'd prefer to be a bit more accurate to be honest... :-) |
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New Sun 12 May 13 16:28
Steering angles - Londoner
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Thanks to NC for taking the trouble to collect and present the data in his usual professional manner. Since he has expertise in the field, I obviously take his views very seriously. I have a follow-up question (addressed to everybody, not just the OP). Why does the steering on RWD cars feel better? Is it because we EXPECT it to, and therefore convince ourselves that it is? I don't think that if I am deluding myself in favouring RWD - but maybe I am. |
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New Sun 12 May 13 16:50
Steering angles - WillDeBeest
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I'm not convinced it does, at least in the two examples I keep at home. True, I seldom drive either hard enough these days to provoke torque steer, which was certainly a feature of previous FWD cars I've had, but in normal cornering the Volvo's steering gives me all the information I could wish for, with a good impression of mechanical connectedness; the Mercedes steering, on the other hand, feels more like asking the butler to ask the knives-and-boots boy to adjust our direction. They're very well trained, and we always seem to get round, but it doesn't feel like just me and the machinery. This can't be just a FWD / RWD dichotomy; there are too many other factors at work. I suspect the LEC will feel pointier once it's wearing at least a couple of Michelin tyres, rather than the Nankook / Nexen cocktail it came with, and it does weigh 300kg more. There's also the blunting effect of the automatic box to consider: it seldom pulls as crisply out of a corner as a manual purposefully snicked into third. So a lot of apples-to-mackerel comparisons, probably. |
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New Sun 12 May 13 17:02
Steering angles - Runfer D'Hills
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Now y'see my E feels really taught on turn in, but in fairness it differs in that it has ( allegedly ) "sports" suspension and beer barrels for wheels. As for holding or selecting the right gear it has the flappy paddles to aid that so all in all it can be set up however you want. I am a complete re-convert to the pleasures of RWD. I'd go so far as to say I actually enjoy driving again having found myself tiring of it a bit sometimes in recent years. |
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New Sun 12 May 13 17:07
Steering angles - WillDeBeest
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| So which bit of that satisfaction is attributable to its being RWD, Humph? |
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New Sun 12 May 13 17:15
Steering angles - Zero
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There is little doubt that RWD and FWD feel different, but I don't think either is more satisfying, both can be enjoyed in their different ways. I suspect Humphs enjoyment may be as a result of the entire package. |
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New Sun 12 May 13 17:20
Steering angles - Runfer D'Hills
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| Can't define it to be honest. Just feels right somehow being shoved rather than pulled. |
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New Sun 12 May 13 17:57
Steering angles - WillDeBeest
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...being shoved rather than pulled. But surely you are being shoved in either? The force you experience is exerted mostly by the seat, which is mostly behind you. And the sensations of movement of the car come from the effect of transferring the car body's mass from end to end or side to side, which must depend far more on rates of forward or lateral acceleration than which wheels are driving. The LEC does have less tendency to spin the wheels in a tight, wet turn - although I (inadvertently) managed even that last night, with a yellow warning light to prove it - but that could equally be achieved with a more conservative traction control program. |
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New Mon 13 May 13 08:22
Steering angles - Cliff Pope
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I've hardly ever driven a FWD car, favouring traditional old RWD models, but when I do I am immediately struck by how much hard work it is. One way of describing the difference is it's analogous to steering a flat bottomed dinghy with an outboard compared to a long-keeled boat with a proper rudder. RWD seems more relaxed. The car largely steers itself, and follows the road in a lazy kind of way, with just a light fingertip correction occasionally. On straightening after a corner the wheel spins slowly back to straight ahead, lightly brushing the fingers. Someone watching might imagine that it was only a dummy steering wheel, the real effort being done by someone else. Contrast FWD, which seems to need two hands constantly gripping the wheel, a bit like those scary camera clips in a racing car. If I let go of the wheel after a corner the wheel spins violently back to straight and then overshoots if not gripped firmly. But perhaps I am not comparing comparable cars? The Volvo 240 is relaxed and easy to steer, my daughter's Peugeot 306 feels like hard work. Both have power steering of course. But even the Triumph and the old LandRover have light steering compared with the Peugeot. |
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New Mon 13 May 13 08:59
Steering angles - sooty123
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>> I've hardly ever driven a FWD car, favouring traditional old RWD models, but when I >> do I am immediately struck by how much hard work it is. >> One way of describing the difference is it's analogous to steering a flat bottomed dinghy >> with an outboard compared to a long-keeled boat with a proper rudder. >> >> RWD seems more relaxed. The car largely steers itself, and follows the road in a >> lazy kind of way, with just a light fingertip correction occasionally. On straightening after a >> corner the wheel spins slowly back to straight ahead, lightly brushing the fingers. Someone watching >> might imagine that it was only a dummy steering wheel, the real effort being done >> by someone else. >> >> Contrast FWD, which seems to need two hands constantly gripping the wheel, a bit like >> those scary camera clips in a racing car. If I let go of the wheel >> after a corner the wheel spins violently back to straight and then overshoots if not >> gripped firmly. >> But perhaps I am not comparing comparable cars? The Volvo 240 is relaxed and easy >> to steer, my daughter's Peugeot 306 feels like hard work. Both have power steering of >> course. >> But even the Triumph and the old LandRover have light steering compared with the Peugeot. >> I've never driven a RWD car before, but it sounds like something might have been wrong with the 306? I've driven a couple of 306s and sounds nothing like the ones I've driven particularly with regard to 'which seems to need two hands constantly gripping the wheel, a bit like those scary camera clips in a racing car. If I let go of the wheel after a corner the wheel spins violently back to straight' sounds a bit dangerous to me. Something does sound amiss as you found 'old LandRover have light steering compared with the Peugeot.' I've driven all sorts of LRs and found them all to be rubbish to drive; hard work, heavy steering more like a tractor than a car. |
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New Mon 13 May 13 08:33
Steering angles - TeeCee
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>> Why does the steering on RWD cars feel better? >> Precise and predictable throttle steer. Choose the amount of oversteer you want. |
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New Mon 13 May 13 11:26
Steering angles - WillDeBeest
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Precise and predictable throttle steer. Choose the amount of oversteer you want. Really? I know we read about this stuff, and I've experienced it in karts and in a (FWD) rally-prepared Peugeot 106 on a gravel track, but on public UK roads? If you can see clearly through the corner you can take it at 60 without slowing down, and if you can't then inducing loss of adhesion when there might be something coming the other is on the spectrum between questionable and irresponsible. In any case, modern cars have so much grip, and so many systems to ensure we don't lose it, that I find it hard to think of a real-road situation where TC's throttle-steer could be both achievable and safe. In the days of the Triumph Stag, maybe, but today? |
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New Sun 12 May 13 17:27
Steering angles - No FM2R
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Steering must cause more than no wear. May not be much, but it must be more than none, and mostly to the steering wheels. Driving must cause more than no wear. Again, more than none, and mostly to the driving wheels. Cornering must cause more than no wear, but I'd guess cornering causes wear to all wheels as close to equally as not to matter in the real world. So, do I want the steering and driving on one pair of wheels, or do I prefer the wear more shared? And in any case, I shouldn't think it makes any level of difference to either outweigh other benefits or the importance of personal preference - and I like the feel of RWD more. |
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New Sun 12 May 13 17:57
Steering angles - ....
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>> Prompted in another thread by a mention of the old nonsense of "asking front wheels >> to do too much", I've looked at some steering angles. >> Always gets a reaction ;-) Of course its rubbish but always gets trotted out to justify RWD. |
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New Sun 12 May 13 18:30
Steering angles - Runfer D'Hills
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Like I said, I can't define it but I know what I mean, if you see what I mean... I perhaps delude myself that I can "feel" the road through the steering wheel and the forces driving the car with my backside and it just feels better with RWD to me. We all have our little peccadillos though I suppose. |
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New Sun 12 May 13 19:14
Steering angles - WillDeBeest
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| Indeed so, Humph. Mine like rolled oats, treacle and beer. What do you feed yours on? |
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New Sun 12 May 13 19:32
Steering angles - Number_Cruncher
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>>Interesting, similar to how a motorcycle steers perhaps? Yes - I suppose it's easier to see that a motorcycle rear wheel must be contributing cornering force pro-rata. The 4 decimal places were just how the numbers came out of MATLAB, I certainly don't trust the numbers to anything like that level of accuracy! All sorts of complications get in the way, perhaps one of the largest being the way that the tyres will adopt some slip angle as soon as there's some cornering force. One of the main messages I try to teach my students is the importance of reducing the vehicle's mass, and being in control of where the centre of mass actually lies - both front/rear, and up/down. In this regard, front wheel drive cars tend to be front heavy, and it is this which explains most of their behaviour with respect to driving feel and dynamics. Although BMW tend to make a big song and dance about 50/50 weight distribution, MB RWD cars tend to be pretty close to this condition too. |
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New Mon 13 May 13 01:19
Steering angles - Armel Coussine
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Although it's obvious, N-C, you nowhere point out that a half g corner at 10mph is quite sharp - has a small radius - while a half g corner at 100 has a much, much bigger radius. A car cornering at high speed on any road has virtually invisible steering angles, even when a touch of opposite lock is needed (owing perhaps to road unevenness and knackered dampers - they nearly all are when seriously needed in a non-sporting car that's done some miles). Hard to spot unless you are in the vehicle or actually driving it. And what does 'the steering angle is comparable to the slip angle' mean? It can't be the same as the slip angle, because if it was the car wouldn't turn at all, as e.g. on black ice. If what you mean is that the steering angle is in some way proportional to the slip angle, then fine... but it should always be much the same if the lateral g is the same, provided the road surface is smooth (at very high speeds, a ripply surface will unsettle a car and increase slip angles, especially if it has knackered dampers/suspension bushes etc., see above). 'Steering wheel angles of more than 10 degrees at speeds of 60mph and above are rare'. Well of course they are. Who wants exaggerated slip angles, tyre squeal and possible loss of control? Violent evasive action pn any road at any sort of cruising speed is a very high-risk moment. Sends a lot of innocents into the scenery or up trees. You know a lot N_C, I don't doubt it for a moment. But this sort of thing reminds me of why I gave up science at 16 and chose chattering and yibbling instead. The bleeding obvious to four decimal places? Do me a favour. But as I say, you have much to tell us. Last edited by: Armel Coussine on Mon 13 May 13 at 01:21
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New Mon 13 May 13 01:29
Steering angles - Armel Coussine
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An interesting thing about cornering on a two-wheeled vehicle, pushbike or motorbike, is that the first steering movement is in the wrong direction, to make the bike 'lean' in the direction of the corner. After that a very small steering input in the right direction, balancing the bike's speed and the radius of the corner, lasts until the bike is running straight again. Radical slip angles are to be avoided at all costs on a bike. Ask any biker, anyone who often rides even a pushbike, or watch terrifying superbike racing on the box. This too is obvious if you think about it, the initial turn in the wrong direction (or so I have been told). But I have never, ever, been able to identify the action or the moment when riding any kind of bike. It's very subtle and wholly instinctive. Last edited by: Armel Coussine on Mon 13 May 13 at 01:32
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New Mon 13 May 13 06:51
Steering angles - swiss tony
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>> This too is obvious if you think about it, the initial turn in the wrong >> direction (or so I have been told). But I have never, ever, been able to >> identify the action or the moment when riding any kind of bike. It's very subtle >> and wholly instinctive. >> It's a light push on the handlebar.. Right to go right, left to go left, then let the bike run, until it's time to change direction again. If you give a 'very small steering input in the right direction' the the bike will sit up, and run straight again.... You can on some bikes feel it trying to drop to one side, if you push the bar whist stationary. |
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New Mon 13 May 13 06:58
Steering angles - swiss tony
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| There are of course other matters such as weight transference (hence the racers getting 'off' the bike) but that's enough for time time in the morning lol. |
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New Mon 13 May 13 19:58
Steering angles - Lygonos
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FWD or RWD nothwithstanding I do somewhat regret not buying a new Integra Type R soon after qualifying in the late 90s. £20k for a car when my salary was £15,800pa (+ 40% shift allowance for 32hrs/wk overtime) just seemed a bit excessive and I kept my pop-up headlamped Prelude 2 more years. |
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