Advantages of 4WD on ordinary saloons?

[tonyb1968]

I'm confused by your reply here, what part is myth and what part is fact? If the first sentence is myth then everything after that is what people have been saying, if its all myth... well, then you have not listened to many on here.

ericmcn said:

Myth:

All-wheel drive systems do not increase the ‘grip’ of a tyre. Four-wheel drives have a traction advantage over two wheel drives because all four tyres can contribute but, ultimately, the grip of a vehicle is dictated by the performance of the rubber on the road.

This particularly applies to during cornering where the speed of the car is governed, not by the driven wheels, but more by the weight-distribution of the car, centre of gravity, tyre performance and suspension system.

There are exceptions to all of the examples given, and the above is intended only as a general guide to help you start thinking about which layout best fits your requirements, but as always, the best approach is to get out there and start test driving.

[GravelBen]

nickfrog said:

And what happened there https://www.youtube.com/watch?v=STaximkaQxo?

Wrong type of ice ? Wrong type of LSD ? I thought 4wd brought stability too ? And that's where 4wd is supposed to excel at (pure traction).

Or could it be on the wrong tyre ?

That one is a pretty extreme example to be fair, the Forester is wearing these tyres (and from memory of comments on the original video, quite worn ones):



If anything its impressive that it got up the hill at all wearing rubber like that in those conditions.

I'd be much more interested in a comparison with a 4wd car on normal all-round tyres (or even an SUV on all-terrains), because thats what most people with regular 4wd cars tend to actually use.

[tonyb1968]

GravelBen said:

nickfrog said:

And what happened there https://www.youtube.com/watch?v=STaximkaQxo?

Wrong type of ice ? Wrong type of LSD ? I thought 4wd brought stability too ? And that's where 4wd is supposed to excel at (pure traction).

Or could it be on the wrong tyre ?

That one is a pretty extreme example to be fair, the Forester is wearing these tyres (and from memory of comments on the original video, quite worn ones):



If anything its impressive that it got up the hill at all wearing rubber like that in those conditions.

I'd be much more interested in a comparison with a 4wd car on normal all-round tyres (or even an SUV on all-terrains), because thats what most people with regular 4wd cars tend to actually use.

These are the reason I nearly curbed my brand new alloy wheels on my Subaru in the snow!

[ericmcn]

Subaru Legacies love snow...this would give the BMW a decent run for its money

https://www.youtube.com/watch?v=eBGhnPCaLYU

[nickfrog]

ericmcn said:

most of the bashing is probably done by people who dont own an AWD...

Myth:

All-wheel drive systems do not increase the ‘grip’ of a tyre. Four-wheel drives have a traction advantage over two wheel drives because all four tyres can contribute but, ultimately, the grip of a vehicle is dictated by the performance of the rubber on the road.

Eric, thanks for posting this, I am so glad we got there in the end, however many pages it took, it would have been worth it

Now, will you need another 30 odd pages to look into the traction circle ?

[Mr Tidy]

ericmcn said:

Subaru Legacies love snow...this would give the BMW a decent run for its money

https://www.youtube.com/watch?v=eBGhnPCaLYU

I'm sure it would be better than most BMWs - but then it has 4WD and must be on winter tyres to be able to perform like that!

So have we finally reached the point where we agree that in snow the ultimate choice is a 4WD on winters, but a 2WD on winters is a better option than a 4WD on summers? I really hope so!

[Flibble]

ericmcn said:

many cars have no soul now, gutless and no driver engagement whatsoever, the legacy is a joy to drive - otherwise i would not have it over 2 years. a bloke on UK Legacy had this to say about the much 'loved' BMW 530d, its probaby similar case for many other marques nowadays.

BRZ no AWD and not fast enough, same as the GT86 - I like the BRZ though as its quite rare.

Odd you should say that, given the BRZ is as fast as your Legacy and almost certainly much faster round corners, not to mention better handling.

Mr Tidy said:

ericmcn said:

Subaru Legacies love snow...this would give the BMW a decent run for its money

https://www.youtube.com/watch?v=eBGhnPCaLYU

I'm sure it would be better than most BMWs - but then it has 4WD and must be on winter tyres to be able to perform like that!

So have we finally reached the point where we agree that in snow the ultimate choice is a 4WD on winters, but a 2WD on winters is a better option than a 4WD on summers? I really hope so!

It shouldn't be too contentious to say that any car on winters is going to beat any car on summers, regardless of driven wheels. Unless you're eric of course, in which case a tired old Legacy beats all comers.

[ericmcn]

nickfrog said:

Eric, thanks for posting this, I am so glad we got there in the end, however many pages it took, it would have been worth it

Now, will you need another 30 odd pages to look into the traction circle ?

its pretty common knowledge, however without winter tyres a AWD still handles better in all conditions over a FWD/RDW with similar tyres, if you put on snow tyres, well then its in a different league entirely to navigate snow and ice

[ericmcn]

Flibble said:

ericmcn said:

many cars have no soul now, gutless and no driver engagement whatsoever, the legacy is a joy to drive - otherwise i would not have it over 2 years. a bloke on UK Legacy had this to say about the much 'loved' BMW 530d, its probaby similar case for many other marques nowadays.

BRZ no AWD and not fast enough, same as the GT86 - I like the BRZ though as its quite rare.

Odd you should say that, given the BRZ is as fast as your Legacy and almost certainly much faster round corners, not to mention better handling.

I will stick to my Legacy with AWD, thank you - Sounds far better too.

Legacy

Engine power 243 bhp
Engine size 3000 cc
Brochure Engine size 3.0 litres
Acceleration (0-60mph) 6.5 seconds
Top speed 151 mph
Drivetrain Four Wheel Drive

BRZ

Engine power 197 bhp
Engine size 1998 cc
Brochure Engine size 2.0 litres
Acceleration (0-60mph) 7.6 seconds
Top speed 140 mph
Drivetrain Rear Wheel Drive

[schmalex]

gizlaroc said:

Thank fk he didn't buy an Audi A6 diesel, he probably wouldn't be with us anymore.


The F11 is a bit dull compared to the E61, but it is a luxury barge, that is the point of it.
Why the 530d and not the 530i or 535i?

I have a 535i. It’s one of the most dull cars I’ve ever owned.

I drive my Panda 4x4 whenever I can as it’s so much more fun!

[InitialDave]

ericmcn said:

its pretty common knowledge, however without winter tyres a AWD still handles better in all conditions over a FWD/RDW with similar tyres, if you put on snow tyres, well then its in a different league entirely to navigate snow and ice

So you have quietly segued into accepting that tyres matter, I supppse that's something.

But no, AWD does not handle better in all conditions than FWD/RWD.

Edited by InitialDave on Friday 19th October 08:23

[anonymous-user]

ericmcn said:

its pretty common knowledge, however without winter tyres a AWD still handles better in all conditions over a FWD/RDW with similar tyres, if you put on snow tyres, well then its in a different league entirely to navigate snow and ice

Not in all, some. And ‘better’ equals more safely.

[Finlandia]

Took some time, but we got there in the end. Any car on winter tyres is better than any other car on summer tyres when driving on ice and snow.

As for the M5 and 530D, I know the feeling all too well, I was sorely disappointed in the Mondeo i test drove, I thought it would have a little bit of the same as the GT, you know both being Ford and petrol...

[996TT02]

ericmcn said:

Disadvantages

Front-drive cars use a device called a ‘constant velocity’ joint or CV joint which allows the drive shaft to turn with the steering wheels but the limited dexterity of the CV joint also has a limitation on maximum steering angle and turning circle.

All the rest is really quite spot on, but the above - well, not for practical purposes, no.

A CV joint can handle quite extreme angles - you only need to handle a halfshaft to realise that it can handle greater angles than the actual ones allowed by the suspension design and related lock-stops.

But extreme steering angles are not that desirable anyway even if one eliminates issues such as tyre rub etc. I once owned a Triumph Spitfire and that is capable of more extreme angles than the norm. On full lock, in a gravel car park, the car tended to push through the gravel rather than steer. This while manoeuvering, not hooning.

In reality viable steering angles are limited by bodywork, not CV joints, even though theoretically you are correct.

[gizlaroc]

schmalex said:

I have a 535i. It’s one of the most dull cars I’ve ever owned.

I drive my Panda 4x4 whenever I can as it’s so much more fun!

Yeah, I had a 335i, I found that dull and went back to a NA M3.

But, I also have a 530d Touring, just imagine your 535i with a diesel engine in it. Eurgghh!!

[Flibble]

ericmcn said:

I will stick to my Legacy with AWD, thank you - Sounds far better too.

Legacy

Engine power 243 bhp
Engine size 3000 cc
Brochure Engine size 3.0 litres
Acceleration (0-60mph) 6.5 seconds
Top speed 151 mph
Drivetrain Four Wheel Drive

BRZ

Engine power 197 bhp
Engine size 1998 cc
Brochure Engine size 2.0 litres
Acceleration (0-60mph) 7.6 seconds
Top speed 140 mph
Drivetrain Rear Wheel Drive

You're quoting the auto gearbox there. Manual is faster (shorter ratios). Variously tested here at around 6.4s: https://www.0-60specs.com/subaru-brz-0-60-times/

Also power to weight:
BRZ: 197 bhp / 1.25t = 157.6 bhp/ton
Legacy: 243 BHP / 1.44t = 168.75 bhp/ton

Pretty close, and once you take into account higher drivetrain losses for the Legacy you can see why the 0-60 times are almost identical.
Better aero on the BRZ too if we're comparing.

[mcpoot]

Nanook said:

I'm glad our resident fanboy likes his car, but has anyone else here driven one? The NA 6 cylinder?

Tedious does not cover it. I mean it's a really dull car.

Eric is ........ well he's just Eric being Eric.

A Spec-B may not be the world beater some proclaim it to be but dull it's not. Drives just like an Impreza only larger but maybe you find them dull too.

[downhillmalins]

x-drive variants and the like have been common place on the continent for quite a while. Just have been less popular/ not available in the UK market till reasonably recently, last 5 years or so I'd say they have become popular here.

I remember seeing a battered old xdrive e46 in a french ski resort a while back and loads of them around Munich.

[neil1jnr]

gizlaroc said:

schmalex said:

I have a 535i. It’s one of the most dull cars I’ve ever owned.

I drive my Panda 4x4 whenever I can as it’s so much more fun!

Yeah, I had a 335i, I found that dull and went back to a NA M3.

But, I also have a 530d Touring, just imagine your 535i with a diesel engine in it. Eurgghh!!

I have 535d. It isn't the best drivers car, but does it's job well on the 90 mile a day commute. I'd prefer the diesel over a 535i if I am honest...but would prefer a 5 series over an equivalent A6 in the majority of cases. Imagine an A6 in comparison to the 5 series...

[InitialDave]

mcpoot said:

Drives just like an Impreza only larger but maybe you find them dull too.

That sounds like what I'd expect, and yes, I did. Competent enough, but not very interesting to drive.