Advantages of 4WD on ordinary saloons?
Discussion
otolith said:
Your four tyres have exactly the same amount of grip. You just can’t use all of it for acceleration if you are only driving two of them. You can’t brake or corner any harder.
Grip and traction are not the same thing.
The two get confused a lot indeed. 4wd adds zero lateral grip, if anything it reduces it slightly because of the added weight and therefore added weight transfer, increasing the effect of centrifugal force. But it does indeed add traction in low friction environments although of course for me addressing the issue at the contact patch is a smarter solution, plus of course 4wd doesn't add anything under braking unlike winter compounds. Obviously a belt and braces approach trumps that but then you have to carry it all year round, although it does make for a point and squirt weapon if you can't be bothered using throttle modulation, which is fair enough.Grip and traction are not the same thing.
nickfrog said:
otolith said:
Your four tyres have exactly the same amount of grip. You just can’t use all of it for acceleration if you are only driving two of them. You can’t brake or corner any harder.
Grip and traction are not the same thing.
The two get confused a lot indeed. 4wd adds zero lateral grip, if anything it reduces it slightly because of the added weight and therefore added weight transfer, increasing the effect of centrifugal force. But it does indeed add traction in low friction environments although of course for me addressing the issue at the contact patch is a smarter solution, plus of course 4wd doesn't add anything under braking unlike winter compounds. Obviously a belt and braces approach trumps that but then you have to carry it all year round, although it does make for a point and squirt weapon if you can't be bothered using throttle modulation, which is fair enough.Grip and traction are not the same thing.
blade7 said:
nickfrog said:
Obviously a belt and braces approach trumps that but then you have to carry it all year round, although it does make for a point and squirt weapon if you can't be bothered using throttle modulation, which is fair enough.
Lol, you do spout some twaddle. Near where I live there's a roundabout on the A1 with a small B road entering either side. There's no slip roads, and in rush hour if you d*cked about modulating the throttle from those B roads you'd get T-boned. With quattro the only thing I have modulate is boost.nickfrog said:
It's well known that Quattro gives infinite traction near where you live. I am not sure you understand what throttle modulation even means, which probably explains why you need 4wd. I'd love to know what part of my post is twaddle though, but not holding my breath.
You know where I live? Is this you stalking me again...My brother raves on and on about winter tyres, on smaller rims than standard etc. but he has an MX5. (Yes that IS true, he exists and has an MX5).
Having owned many cars of differing drivetrains (true also)I can confirm, that on non winter specific tyres AWD has better traction off the line.
Braking is another matter and has zilch/nada to do with how the wheels are driven, unless you are talking about ‘engine breaking’:
Oh the horror!!!
Having owned many cars of differing drivetrains (true also)I can confirm, that on non winter specific tyres AWD has better traction off the line.
Braking is another matter and has zilch/nada to do with how the wheels are driven, unless you are talking about ‘engine breaking’:
Oh the horror!!!
Edited by Hol on Sunday 7th October 18:33
I want awd/4wd for added grip in wet and snowy conditions, yes I’ve managed without it for the last 17yrs and it doesn’t snow half as much as it used to but a few reasons,
On a dry day my gti will happily keep with my mates s3 and there’s not much in it but a few week back on the moors it was raining we were making progress and I genuinely couldn’t keep up after the corners he just fired straight out of them yet in the dry I stay with him, all I got was wheel spin traction control and understeer whereas he just gripped and went!
And secondly he fits winter tyres to his and it managed to get up Sutton bank in rly bad snowy conditions behind a Range Rover and anyone that knows Sutton bank will know how steep it is! My golf on winters doesn’t get anywhere near and for my job I’m going up and down the moors On a regular basis so it will benefit me!
On a dry day my gti will happily keep with my mates s3 and there’s not much in it but a few week back on the moors it was raining we were making progress and I genuinely couldn’t keep up after the corners he just fired straight out of them yet in the dry I stay with him, all I got was wheel spin traction control and understeer whereas he just gripped and went!
And secondly he fits winter tyres to his and it managed to get up Sutton bank in rly bad snowy conditions behind a Range Rover and anyone that knows Sutton bank will know how steep it is! My golf on winters doesn’t get anywhere near and for my job I’m going up and down the moors On a regular basis so it will benefit me!
blade7 said:
You know where I live? Is this you stalking me again...
I can't remember ever stalking you. Look, I know you enjoy being hostile on the internet. You like/need 4wd on road cars and that's great. I don't, whether on the road or on track. Live with it. Ignore my views if they get to you and I'll ignore yours. Deal ?Norfolkandchance said:
Well, we are opposites then. I like tail happy cars. But I realise that some don't. I once sold an E30 325i to a journalist from Evo who crashed it, apparently due to its tail happyness, on a motorway slip road! However, I'm not talking about a 330d, I'm talking about a 320d. And Audis, where the alternative is FWD and therefore not tail happyness.
Was that Stuart Gallagher by any chance?One of my friends had a 2.8 XR4x4 at the same time I had the normal XR4i. It was pretty sure-footed but not as quick in a straight line, bit thirstier and, for me personally, not as much fun to drive
Popular with police though as they could drag cars out the way with the 4wd in wet/muddy conditions
In the dry, RWD cars are absolutely fine. And off the line better than FWD as the weight transfers to the rear and presses the tyres hard to ground. I think FWD cars are more predictable and safer for the average driver who doesn't understand the mechanics of it all. In damp, greasy, poor weather conditions AWD certainly delivers better performance, but then I don't hoon around in those conditions anyway. I'm sure there are have been many accidents in AWD cars where over confidence is to blame.
Interestingly didn't Top Gear pitch a 911 Carrera 2 against the 4WD version and the 2WD car was faster around the (dry) circuit?
I'm sure it was.
Tyre choices are also critical. And this is a big issue, because how many people opt for cheap tyres these days? The car they own once having premium rubber fitted when brand new, now shod with cheap crap negating much of the advantage of the 4WD system come first change.
Interestingly didn't Top Gear pitch a 911 Carrera 2 against the 4WD version and the 2WD car was faster around the (dry) circuit?
I'm sure it was.
Tyre choices are also critical. And this is a big issue, because how many people opt for cheap tyres these days? The car they own once having premium rubber fitted when brand new, now shod with cheap crap negating much of the advantage of the 4WD system come first change.
Edited by Lincsls1 on Sunday 7th October 23:00
nickfrog said:
otolith said:
Your four tyres have exactly the same amount of grip. You just can’t use all of it for acceleration if you are only driving two of them. You can’t brake or corner any harder.
Grip and traction are not the same thing.
The two get confused a lot indeed. 4wd adds zero lateral grip, if anything it reduces it slightly because of the added weight and therefore added weight transfer, increasing the effect of centrifugal force. But it does indeed add traction in low friction environments although of course for me addressing the issue at the contact patch is a smarter solution, plus of course 4wd doesn't add anything under braking unlike winter compounds. Obviously a belt and braces approach trumps that but then you have to carry it all year round, although it does make for a point and squirt weapon if you can't be bothered using throttle modulation, which is fair enough.Grip and traction are not the same thing.
Similar with braking, depending on the 4wd system (probably doesn't apply to haldex on-demand stuff) the torque transfer through the drivetrain can resist the tendency for individual wheels to lock on mixed grip surfaces or when they are unloaded. Will it give you a shorter ABS-activated emergency stopping distance? Nope. But it can help you maintain control and stability in difficult conditions.
In both cases the advantage is less about peak steady-state performance and more about a wider envelope in transient states.
It just seems a nonsense on many cars, fitted with huge wheels and skinny tyres in the middle of Winter. Having the wrong tyres fitted then expect the worse, you may get going with these systems but try stopping and turning just in general and not in an emergency....
Strangely enough I don't know if it is just me but in a majority those driving like "idiots" in poorer conditions tend to be those with some description of AWD/4WD. I am not saying all our but my experience generally says it will be.
I cannot for a moment understand the requirement by those that a RWD in light greasy conditions end up with the TC light illuminating, I think many cars probably would if you go pedal to the metal with little regard to the level of throttle input and the conditions.
Winter tyres does make a difference and my 640D was absolutely fine in both sets of snow it went out in. I did notice many kept their distance I suppose BMW's have this "perception" that it could go wrong at any moment because RWD.
Maybe it is because for a number of years now I have owned only solely RWD vehicles, before that only FWD and never any of the AWD/4WD versions. I have driven some xdrive models in that ownership time, and honestly I hated it, I found the whole system just an interference that had an odd "balance"
If you own RWD (and pretty much any car ignoring drivetrain for a moment) then additionally have a proper alignment done can massively alter the feeling and balance of the car. My MX5 originally was in specification but the rear was all over the show, and explained the skittish behaviour in the wet, one proper alignment later and it was a different car entirely....
I will ultimately agree though driving RWD does require more level of concentration and slowing in poorer conditions more, but then only clowns don't slow down in the poorer conditions and leave greater distances between them and other objects.
Strangely enough I don't know if it is just me but in a majority those driving like "idiots" in poorer conditions tend to be those with some description of AWD/4WD. I am not saying all our but my experience generally says it will be.
I cannot for a moment understand the requirement by those that a RWD in light greasy conditions end up with the TC light illuminating, I think many cars probably would if you go pedal to the metal with little regard to the level of throttle input and the conditions.
Winter tyres does make a difference and my 640D was absolutely fine in both sets of snow it went out in. I did notice many kept their distance I suppose BMW's have this "perception" that it could go wrong at any moment because RWD.
Maybe it is because for a number of years now I have owned only solely RWD vehicles, before that only FWD and never any of the AWD/4WD versions. I have driven some xdrive models in that ownership time, and honestly I hated it, I found the whole system just an interference that had an odd "balance"
If you own RWD (and pretty much any car ignoring drivetrain for a moment) then additionally have a proper alignment done can massively alter the feeling and balance of the car. My MX5 originally was in specification but the rear was all over the show, and explained the skittish behaviour in the wet, one proper alignment later and it was a different car entirely....
I will ultimately agree though driving RWD does require more level of concentration and slowing in poorer conditions more, but then only clowns don't slow down in the poorer conditions and leave greater distances between them and other objects.
The other consideration when comparing 2wd/4wd/fwd/rwd systems is the differential types used on both axles.
I think its fair to say that (nearly all) FWD and to a lesser extent RWD cars use open diffs which means when the conditions get slippy the car pretty much becomes a 1WD vehicle!
Out in my van back in the snow, pulled over on to the verge to take a call. One side of van on the snow, the drivers side on good clear road. Could I move off? Nope! The open diff sending all the power to the wheel with no traction. Brilliant stuff!
Now a car with a LSD either FWD or RWD would have locked the axle and in my case wouldn't have got stuck.
There are also many 4WD cars that use open diffs as well and in this scenario the results could easily have been the same!
I think its fair to say that (nearly all) FWD and to a lesser extent RWD cars use open diffs which means when the conditions get slippy the car pretty much becomes a 1WD vehicle!
Out in my van back in the snow, pulled over on to the verge to take a call. One side of van on the snow, the drivers side on good clear road. Could I move off? Nope! The open diff sending all the power to the wheel with no traction. Brilliant stuff!
Now a car with a LSD either FWD or RWD would have locked the axle and in my case wouldn't have got stuck.
There are also many 4WD cars that use open diffs as well and in this scenario the results could easily have been the same!
ghost83 said:
And secondly he fits winter tyres to his and it managed to get up Sutton bank in rly bad snowy conditions behind a Range Rover and anyone that knows Sutton bank will know how steep it is! My golf on winters doesn’t get anywhere near and for my job I’m going up and down the moors On a regular basis so it will benefit me!
Sounds like we're from the same neck of the woods. When people say they've driven their 400hp, semi-slick shod RWD car in snow with 'no trouble at all' I usually assume that means they've negotiated the 3% gradient out of their cul-de-sac followed by a few miles of treated suburban roads with a few patches of slush here and there, then a dual carriageway/motorway which is basically just wet. We need to run a 'Sutton Bank summer tyre/2wd challenge' in the snow to really put these claims to the test!While I do see a benefit to having 4wd on a 'normal' car and would always choose it myself, I would say from a fair bit of experience of driving in snowy conditions in recent years that in order of importance what you want is 1. wInter tyres, 2. decent ground clearance, 3. 4wd. Of course in the south (or even oop north if you don't venture into upland areas) you may go years between seeing any proper snow so ground clearance is not nearly as important.
Norfolkandchance said:
I once sold an E30 325i to a journalist from Evo who crashed it, apparently due to its tail happyness, on a motorway slip road!
In fairness, my E30 325i is the only car I've found myself applying opposite lock on a slip road. They do like to wiggle their arse a bit!4WD can be very impressive, but whether you like the dynamics of how it drives can be very subjective. I've driven some AWD cars that felt good and some I really didn't get on with.
Plus, to paraphrase PJ O'Rourke, "four wheel drive allows you to get yourself mired axle-deep in mud twice as far into the woods as can be achieved with two wheel drive alone".
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