I\'ve never quite got to grips with understanding of this and never quite understood the passion for rear wheel drive.
I had a 3 series beemer and got caught in heavy snow at Matlock watching the RAC Rally some years ago. The snow fell fast and stuck and the BM became almost useless. I had to be pushed up a hill bumper to bumper by a Land Rover at one point. Good job it was a company car.
Since then I\'ve preferred front wheel drive and I\'ve had a couple of Passats and now a Megane. Am I missing out on something? Can someone explain to me like I\'m a 3 year old the advantages and disadvantes of both? What is understeer and oversteer? What driving teqhniques should be applied to get the best out of both?
Thanks, I hope this will clear up a long term gap in my knowledge.
Malcolm
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Put simply, understeer is when the front wheels run wide of the intended turn-in path when you steer to go left or right, oversteer is when the rear wheels attempt to do so; in the case of the latter if you don't catch it in time you could/will go into a spin.
That's why understeer is safer as the tendency is to lift off the throttle which allows the car to turn as intended, rather than run wide.
An explanation can be found at numerous sources. Here's one:
www.dur.ac.uk/r.g.bower/PoM/pom/node31.html
A more detailed alternative is at:
www.neleiam.f9.co.uk/Driving_Info/Under_steer/unde...l
One of the key advantages of rear-wheel drive, amongst others, is that the steering and acceleration of a vehicle are separated - as you will realise the front wheels provide both the steering and drive requirements for a front-wheel drive vehicle.
Here's a Telegraph piece about the 3-Series from back in 1998 that could prove of interest to you:
www.telegraph.co.uk/motoring/main.jhtml?xml=/motor...l
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Thanks for that, I\'m wiser now. I\'ve heard something obout accellerating into a bed or out of a bend dependent on whether driving FWD or RWD. Which applies to which please?
Malc
Malcolm
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You should approach corners at a speed comensurate with being aware in good time of possible hidden dangers or being sharper than expected and accelerate out of the corner once you know it is safe to do so.
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Thanks for that, I'm wiser now. I've heard something obout accellerating into a bed or out of a bend dependent on whether
driving FWD or RWD. Which applies to which please?
It's a bit of bar-room fibs here - the fastest way around a corner will work if the car is FWD or RWD get most of your braking done in a straight line corner while keeping the car balanced with power and then accelerate out.
However what you've heard stems from the fact that FWD cars* tend to be more tolerant of going into a corner too fast, RWD cars** don't.
*Not all FWD cars
**Not all RWD cars either!
Gareth
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That's an easy one.
Never accelerate into a bend,
and normally don't accelerate out of it either.
Normally maintain the same speed throughout any bend -
it gives your passengers confidence - they may need it!
Most skids (over- or understeer) are caused by entry speed to bend being too high.
Having got the entry speed right - it may be possible to accelerate out.
This is to be from the apex - so accelerating at same time as straightening the steering. But is, of course, dependant on road surface condition.
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>>Normally maintain the same speed throughout any bend
That could prove somewhat interesting on occasions and not too passenger confidence inspiring at the time.
Older_not_Wiser
One publication that will provide lots of valuable advice and information for you is Road Craft - the police driving manual.
It's readily available and there's probably a copy in your local library.
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"Normally maintain the same speed throughout any bend"
Indeed, this was open to mis-interpretation.
Those words should have been preceeded with:-
"Having judged the correct entry speed, . . ."
Roadcraft. Indeed. I endorse everyone having a copy.
As well as current version, I still retain the 1970's version which was used extensively in my training.
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>>>>>>"Normally maintain the same speed throughout any bend"
Pretty boring on a bike. More fun to get down a gear or two, get all your braking done as required before you lay her over, trail the throttle into the bend, clip the apex, and then accelerate out in a low-ish gear. What I was always taught anyway.
Bikes also under- and oversteer too. Japanese cruisers are very prone to the former. The ones I've tried have been anyway.
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>Pretty boring on a bike.
Indeed. Perhaps in a car also. But what I attempt to get through in any training, decelerating (as in some idiots are still braking as they turn) is a big no-no.
And, as for accelerating into a bend - that's when we find out the effect the charateristics of the vehicle have on the handling.
Probably the hard way.
So, at start of understanding, constant speed from entry to apex to exit please.
(this, of course, requiring slight increase in gas to maintain speed.)
When that is demonstrably understood, we can consider chasing the Limit Point after the apex.
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Slow in fast out - wroks for me. Also am I the only one who uses the maximum amount of road (even the wrong side where safe) to minimise direction changes? I never see anyone else doing it.
Classic example is a lovely downhill into a left right left combination you can see is clear from the top of the hill with broken centre white lines and wide road. Minimum steering invoved to straight line it, but everyone rigidly sticks to left lurch, right lurch, left lurch.
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I forgot about being in the correct gear for accelerating out of the corner...:-)
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>>I've heard something obout accellerating into a bed
So have I. Mostly my Mother telling me not to when I was younger.
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Malcolm,
My previous explanation of under vs oversteer is at:
www.honestjohn.co.uk/forum/post/index.htm?v=e&t=21...0
Advantage of FWD is that everything is relatively benign and predictable. Advantage of RWD is that one set of tyres is steering and another is pushing. Hence both can work independently and steering is not affected by power delivery, generally fewer compromises.
Disadvantage of RWD cars is that they tend to oversteer if you get it wrong and that can be distressing if you don't know what to do. Disadvantage of FWD is that as only 2 tyres are doing everything, they can't always do it all at the same time so things can go wrong earlier, albeit less distressingly.
FWD and RWD are both equally hopeless at dealing with deep snow. You need 4WD for that, as you found.
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I have never found FWD bad in snow.rwd yes.
Was mech1
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It has been said that oversteer is when the passenger is frightened, and understeer is when the driver is frightened! However, simply put, both cases happen when cornering, and is due to the fact that the tyres slip against the road when cornering - this is normal and this is how they generate grip. Normally you don't feel anything because the slip angle (the angle between the direction the wheel is pointing and the car is going is quite small. When the slip angle gets bigger more grip is generated (and you corner harder), but there comes a point when more slip angle doesn't generate any more cornering force!
That's what's happening with the dynamics of the tyres, what you feel as the driver:
Understeer is when you turn the front wheels more, and they don't grip, the front of the car is ploughing on and you're not going to make that bend, you're not turning hard enough. You wind on more steering but it doesn't make any difference, you're going to slide off the road.
Oversteer is when the back of the car starts to slide out, they make it look easy on Top Gear or the Dukes of Hazzard but the car is going around a tighter corner than you intended to and you're going to spin off the road backwards.
The cure for any skid is to take away what causes it - assuming a steady state corner (no harsh acceleration or braking) then you can stop understeer by lifting gradually off the power, and then when the wheels do regain their grip don't be shocked if the car swerves a bit as it can be quite sudden. Mild understeer can be cured by winding on more steering. To stop oversteer, you can also gradually lift off the power, or you can steer into it - wind OFF the steering, tending to keep the front wheels pointing where you want to go.
Skidding can be caused by braking too hard, accelerating too hard or even cornering too hard for your speed. Depending on the car, it can understeer or oversteer by doing any of these things.
You can also make any car oversteer or understeer, best tried at low speeds on a slippery surface with plenty of run-off area. Skid pan or snowy carpark! Any car will understeer if you accelerate then turn the wheel hard while still accelerating. In extreme cases, you can be winding the wheel more and then back and it doesn't make any difference to the huge arc your car is going around. You can make any car oversteer by braking hard on the entry to a corner and flick the wheel sharply. Back doesn't slide? Try again only this time as you brake flick the wheel left then right very fast, that will unsettle the rear of the car and you'll be oversteering. Hopefully you printed out this reply and you know how to catch the skid. Then you can try it again!
Gareth
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It has been said that oversteer is when the passenger is frightened, and understeer is when the driver is frightened!
LOL!
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I've also heard it said that the difference between understeer and oversteer is that in the latter, you go through the hedge backwards.
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I once did a lot of driving in a LandRover in deep snow, and the interesting thing was that it displayed both characteristics at the same time, having drive at front and back. The result was a kind of crab-wise gait especially on corners. It was unstoppable, but took up quite a lot of road.
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Oversteer is a Volvo 360 injection with Pirelli tyres that have poor wet traction attached to a car with a reputation for oversteer in damp conditions ..... and ending up sliding on your side for several metres ! Ouch ..... :-(
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Wasn't it Top Gear that did a little demonstration, Hammond on his knees with Dinky toys, to show that oversteer is better because you don't see the tree that kills you?
Whereas with understeer, you see it hurtling towards you, of course...
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..or hurtling towards it as the case may be....:-)
Seriously, to really find out at first hand and in safety, if you know of anyone who owns a reasonably sized area of firm ground who would be prepared to let you loose, you'll find out how much fun power slides can be, the difference between understeer and oversteer and how to correct a skid; it's well worthwhile.
Otherwise there are courses available that will provide such facilities.
I've been lucky enough to use the facilities of test tracks, race tracks and airfields to enjoy such fun - thoroughly recommended.
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It's also worth popping out in heavy snow, if one can drive carefully enough, to a local supermarket or retail park for a bit of low speed sliding.
Providing one is sensible, its a safe way to practice under and oversteer and get used to feeling the car "out of control" IYSWIM
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Just a bit unfortunate it doesn't snow all that often..
I had intended to suggest these type of areas but, unfortunately, apart from the fact that many supermarkets are now open 24 hours a day, such "razzing around" as its termed, usually attracts police attention as a result of Security contacting them.
Shame, as it's a great way for many people to learn in safety if the area is large enough and there's no one around.
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Large gravel carparks as found at posh country hotels also work.
When it snows, there's no need to go the the supermarket. Just stand and watch everyone else go by. You'll see quite enough sliding around to make you want to put the keys away.
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It's also worth popping out in heavy snow, if one can drive carefully enough, to a local supermarket or retail park for a bit of low speed sliding. Providing one is sensible, its a safe way to practice under and oversteer and get used to feeling the car "out of control" IYSWIM
'Low speed' and 'sensible' should be your watchwords - take it from one who ignored this and wrote of his first car, a '53 Ford Prefect, which ended it's days by sliding backwards into a telegraph pole while I was 'playing' on an ice-covered car park. It wasn't supposed to go round 180 degrees!
After the impact my friend in the passenger seat was doubled over groaning in agony and clutching his belly. I was terrified, thinking I'd injured him. Turned out that the large rubber torch that had been on the dashboard had shot back and hit him in a very tender part of his anatomy!
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towards it...
Sorry, too much influence from Einstein. Or perhaps the world revolves around me. Whatever.
........
I've tried a Maserati 4200 on a skid pan, with and without electronics. So much fun they had to lever me out of the driving seat.
Best fun was managing to keep it in a straight line with the electronics off, then watching F-i-L try to do the same but promptly depart stage left!
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I think I have got the hang of this now, but can anyone explain to me what motoring correspondants mean when they describe a car that understeers as having "nose-wide" understeer. I have noticed it in a few articles and I have always wondered.
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Because the nose of the car drifts "wide" of the turn in an oversteer.
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Talking of "drift", whatever happened to the "four wheel drift"? Used to be thrilling watching film of the likes of Fangio, Hawthorn, Collins, Moss etc executing a four wheel drift. Nowadays, F1 cars go round corners like Scalextric cars.
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Marvellous. Only half a day after posting the query, there is the article written up & posted on the net at
www.xxxxxxxxxx.net/forum/cms_view_article.php?aid=8
I just hope everybody who contributed was telling the truth. (Next time he posts, everybody, tell a \'different version\' of the truth...)
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Cheeky little!
Oi, Malcolm, some credits and referred site traffic if you expect to remain on this forum, thank you.
No Dosh
Backroom Moderator
mailto:moderators@honestjohn.co.uk
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Do we need an IHAQ thread re copyright?
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I think someone had better remove that link--it doesn't seem like the kind of thing that would do much good for this site any more.
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Talking of "drift", whatever happened to the "four wheel drift"?
they got bigger, wider, softer compound tyres which allow them to corner faster, but less excitingly.
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The aerodynamic mean that the downforce only works when the car is going forwards, the moment the car starts going sideways the wings don't work, so the keep the car pointing in the right direction to obtain maximum grip through the corner.
Its another good reason to drastically reduce the wing size in F1. Would make for much more interesting racing and would also allow for more overtaking.
The sooner they ban all wings the better.
--
I read often, only post occasionally
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"Cheeky little!"
Yes, but he's given me a great idea for making some money from articles on central heating problems, boilers, removing suncream from upholstery etc!!
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Its quite simple really. Its all about slip angles. Understeer is where the slip angle at the front is larger than the rear during steady state constant speed cornnering- ie just enough throttle is applied to maintain entry speed. Oversteer is the reverse. Few road cars truely oversteer.
In rear wheel drive cars, a drive can provoke power oversteer, this is where an increase in throttle "outguns" the rear tyres and they loose traction. Thus, very skillful drivers can correct for natural uindersteer in a rear wheel drive car.
Understeer can be conbatted in both front and rear wheel drive cars via trail braking.
Spikeyhead has already explained the most important reason why f1 cars are not seen to slide. Another reason is tyre technology and type. Modern low profile slicks creat peak cornering traction at lower slip angles than old fashioned tyres, hence if they were to slide more they would have less grip.
Understeer is not liked in racing as in two wheel drive cars once there is understeer applying more throttle usually makes it worse, so you cannot accelerate out the corner as fast, which reduces the all important exit speed.
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Or even Chapter 5 of Stuart's recommended book.
The one that says
"Because skidding should never be practiced on a public road, there are no suggestions for practising techniques in this chapter"
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Unreserved apologies. Article now removed from Bangernomics.net.
I will place a link to the HJ site by way of further apology. I\'m sorry again for being a little overkeen to populate my new site.
Further I would like to say that my site is totally free for all use and I make it clear that support of site advertisers and sponsors is appreciated to help cover hosting and development costs only.
Anyone can contribute relvant articles on my site and be fully credited and include a link back to their own site in every article. This is standard and built into the system.
My site is dedicated to everything about used cars under £5000. Users may advertise cars for sale in a powerful classifieds system totally free. There are no restriction, they are no special requirements on dealers using the system and anyone can include up to 5 pictures on any ad.
There is a forum of course and a dealer directory categorised by county. Dealers can link to their own sites free of charge too.
Malcolm
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Please also amend your username and refrain from advertising your site within your signature.
Thank you.
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I have apologised, removed the article and placed a link to HJ on my site.
Malcolm
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In an understeer, aren't you supposed to jab the brakes briefly? This causes the front of the car to job; more weight on tyres and hence more grip. I'm sure I saw it in a video about how to control a car on snow.
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I assume you are thinking of cadence braking which, before the advent of ABS, was a method used to help the tyres to grip in slippery or tricky situations.
It's done by pushing the brake pedal on and off rapidly but does take practice to perfect. ABS does the same thing but far, far more efficiently...:-)
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In an understeer, aren't you supposed to jab the brakes briefly? This causes the front of the car to job; more weight on tyres and hence more grip.
This can work, but it's a braver person than me (or with lots of run-off area) who tries it! It can also provoke the car into snap oversteer, so gradually backing off the power is the best way around, carefully winding on a bit more lock if you feel the need to. Beware though, that when the tyres do grip again it can be quite sharp, so more steering lock can make the rear slide too.
Gareth
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Is that the smell of smoke coming out of Mr Hall's ears I detect in my nostrils ?
--
Matthew Kelly
No, not that one.
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bangernomics.tripod.com/book.htm
Mr Ruppert's more likely - whose word it is. Mr Hall merely borrowed the word with permission.
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Oh, and now that Malcolm has removed the articles cribbed directly from Mr hall's site...
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'It's also worth popping out in heavy snow, if one can drive carefully enough, to a local supermarket or retail park for a bit of low speed sliding.'
I remember SWMBO driving to Safeways just after xmas.
It had snowed the night before & although the main roads were clear as they had been gritted, Safeways car park was still covered in snow with ice underneath.
SWMBO started to turn into a parking bay in her heavy Citroen CX estate, but the tyres had other ideas.
SWMBO assured me she was only doing about 5mph when the car hit the curb whith the tyre at 90 degrees to same.
The solid forged lower suspension arm still managed to bend under the strain & SWMBO came home with a red face complaining that the steering didn't feel right.
One new lower suspension arm & wheel later, all was fine for SWMBO's next outing.
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