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View Full Version : AWD versus 4WD what is the truth?


NP2004
12-05-2007, 09:52 AM
I am in the market for a Suv/Sav and wanted to know what are the pros and cons of Awd versus 4wd? I know all the luxury Sav/Suv manufacturers like BMW, MB, Acura and Audi etc. use AWD rather than 4wd. Does that mean these trucks are only made for paved roads and cant do any off road traveling? Are they less capable in the snow or in mud than 4wd trucks since you cant lock into 4wd? I know X5's arent made for serious off roading like a H2 or H3 but how capable are they off road before damaging the vehicle?

Big "J"
12-05-2007, 02:59 PM
From what I understand.... and take this with a grain of salt, that AWD is on all the time. No switching it off as you could with 4WD in a Hummer.

So, depending on your driving habits and the conditions the X5 should handle what ever it gets to a point much like any Hummer.

I personally haven't taken mine off road and probably won't but, if inclement weather hits I'm prepared.

iversonm
12-05-2007, 03:24 PM
In the old days, 4wd systems typically were meant for off road only, as the they did not have differentials in the transfer case. (i.e. between the front and rear axles). You also could lock the hubs on the axles, locking the differentials together, so all 4 wheels turned at the same speed.

This is not useful on dry pavement. More sophisticated systems had a center differential and was designed for continuous use on dry pavement. This was called AWD to differentiate itself from the previous 4WD systems.

As with anything, the distinction between the systems have blurred to the point that the definitions are mostly irrelevant. Pickup trucks have transfer cases that can operate in 2WD, full time AWD, or the old fashioned 4WD.

iversonm
12-05-2007, 03:26 PM
From what I understand.... and take this with a grain of salt, that AWD is on all the time. No switching it off as you could with 4WD in a Hummer.


Actually, the Hummer (H1) has a pretty slick AWD system using Torsen differentials. It can deliver 100% of the torque to 1 wheel with the other three in the air. I have one of the differentials in my office.

Starab
12-11-2007, 10:49 AM
AWD > can be permanently 4 wheel drive system
OR
Active AWD > Usually front Wheel drive eg. Acura MDX OR can be Rear wheel drive eg.xi
This system changes to AWD depending on Road conditions.

4WD > may have Switch > You control 4WD whenever you want.
OR
4WD > has no switch > Permanent 4 wheel drive

jumboSushi
12-14-2007, 01:08 PM
For daily driving, the AWD eats more gas than the 4WD, AWD accelerate slower than 4WD, but AWD performace better on snow or rain. If you have good driving skill, you will find out 4WD are more fun to drive !!

Starab
12-15-2007, 06:19 AM
1-AWD eats more gas than the 4WD,
2-AWD accelerate slower than 4WD,
3-AWD performace better on snow or rain.

1-AWD eats more gas than the 4WD = If AWD is permanent on your car, otherwise 4WD eats more gas than Active AWD, Usually AWDs are FWDs(Honda/Acura) or RWDs (BMWxi) and changes to AWD as needed
2-AWD accelerate slower than 4WD = when it is active AWD
3-Plus AWD is smoother than 4WD

werewolf
01-16-2008, 03:35 PM
BMW X5 traction systems in the X5 differ depending on the year of the X5.

Early versions are AWD with a fixed 35/65 split front to rear wheels. Traction control (DSC) is a combination of the computer controlling the ABS/brakes to regain traction. Compared to competitive products, this really was not that great a design. BTW I have this design

Later versions have X-drive where traction can be directed front wheels to back or vice versa depending on grip. This is still AWD

The best SUVs (from a legitimate off road/tough driving condition perspective) have 2WD, AWD, and 4WD Hi / Low options. Cars that have this include Toyota Landcruisers (oversea models) Infiniti QX4, Chevy Trailblazers etc. Hummer too? These SUV models are built on truck designs. But you are lugging around additional hardware and weight for this..gas penalty

The joy of AWD is that it is always on. The joy of 4WD is that it does perform better in off road/low traction situations.

The Acura/Honda version of AWD works pretty well for most situations. Part-time AWD

IMO tires are the single biggest factor in most low traction situations (snow on road rather than mud off-roading). BMW doesn't equip x5s with very capable off road/low traction tires.

jimsaq
01-21-2008, 01:30 AM
I am in the market for a Suv/Sav and wanted to know what are the pros and cons of Awd versus 4wd? I know all the luxury Sav/Suv manufacturers like BMW, MB, Acura and Audi etc. use AWD rather than 4wd.


The definitions cross over into each other's territory to some degree and if you've never had much exposure to the terms and the vehicles over the years it can be confusing.

wikipedia does a pretty good job of explaining the terms in my opinion:
http://en.wikipedia.org/wiki/4wd


Does that mean these trucks are only made for paved roads and cant do any off road traveling?
not at all - but they will not be as capable after a point, as some other vehicles may be


Are they less capable in the snow or in mud than 4wd trucks since you cant lock into 4wd?
they may be less capable in snow or mud than some other vehicles, but not due to not being able to be locked into 4wd. they are designed by default to always be providing torque to the front and rear ends, so in effect, they are already 'locked' into 4wd - the difference is that torque is not always split 50/50 between the front and rear like a traditional 4wd - the computer system can vary the amount of torque between the front and rear, and can indirectly vary the amount of torque getting to the ground at each wheel by communicating with the abs and possibly other systems to brake individual wheels.


I know X5's arent made for serious off roading like a H2 or H3 but how capable are they off road before damaging the vehicle?
here is where subjectiveness really comes into it. everyone has a different idea of what serious offroading is, and it's usually based soley on an individual's own exposure to terrain - sometimes even by proxy. one thing's for sure - nearly everyone will think that their own version of serious is the global definition of serious :) I go 4wd'ing every other weekend, and I know that when I think back to terrain I might've thought was serious say 6 months ago, I often chuckle at how tame it seems now when I drive it again.

I would say that an X5 is 'quite' capable (subjective again) as anything else on terrain that is only rough enough so as to not come into contact with the underside, if you get what I mean. anything worse than that you will start having issues - but this is essentially true for any vehicle off-road.

the other main factor is the tyres. these vehicles will rarely, if ever, have tyres which work anywhere near as well offroad as they do onroad which will greatly impact their ability to maintain traction off road. this is why I change tyres on my 4wd (nissan patrol) when I go for a weekend of driving in the rough stuff. during the week I run all-terrains, which are said to be 80% road 20% off road. come friday night, I swap out to much larger and chunkier bias ply tyres which are practically useless on bitumen but absolutely fantastic off road.


http://jason.qgl.org/images/4wd/random/_MG_4315-4-web-sml.jpg



in a nutshell, an X5 really isn't an off-road vehicle in a strict sense of the term. but certainly, due to it's AWD system and traction control etc, it will do much better off bitumen than a 2wd vehicle.

I won't take mine off-road, not even onto a good dirt road - I wouldn't want the paint chipped from stones flicking up :) I'm keeping my nissan patrol for off road