geko29

This:

Is in reference to a comment that was a direct reply to this (I even quoted it, so I'm not sure why you're confused):

How exactly does your comment about supercars eating other cars for breakfast have ANYTHING to do with inclement weather? I mean really, who drives their $1.6M, 16 cylinder quad-turbo hypercar in 6" of snow?

I'd also point out that if you would describe Nurburgring as "perfect pavement", we're not talking about the same track. It's an incredibly harsh and bumpy track, which many drivers liken to driving on gravel at triple-digit speeds.

...and zero more traction when trying to steer or stop, which in most cases, are FAR more important with regards to safety in inclement weather than acceleration. In fact, these two critical aspects actually get worse due to the additional weight.

My position is that I don't believe the modest increase in traction/acceleration in slippery conditions 40 days out of the year is a good tradeoff for making the driving experience worse the other 325 days of the year, and operation and maintenance more expensive 365 days per year. Especially considering that, for nearly an order of magnitude less than the cost of an AWD system, I put on snow tires that improve ALL THREE aspects of traction/driving safety in slippery conditions (not just acceleration), and make my very-expensive summer tires (which also improve all three traction functions the other 9 months of the year) last longer as a bonus.

Safer+more fun+ less money=win

Quadro

So you never saw super cars driven on snow, right?

Watch this, where Bentley Continental V8 eats Ferrari FF for breakfast due to superior AWD system despite having 150 less HP and being heavier -- how does that body with your comment that AWD is only useful when you have too much HP?


If additional weight of AWD was detrimental to overall handling compared to RWD you would see RWD cars beating AWD cars in a rally all the time -- except you don't. Snow or not.

Och

iTrader: (3)

That is not necessarily the case. Unless you have a car with a modern torque vectoring system, having AWD might mean a lot less traction trying to get moving. It takes a lot less torque to make front wheels of a car to start slipping on take off, and with a traditional differential/transfer case once these front wheels start slipping, no more torque can't send to rear wheels. The problem is even more pronounced when you're exiting a corner, you can't really get on the throttle without spinning the front tires, which results in sever understeer and premature tire overheat and wear. Essentially a car with traditional AWD system will behave like FWD - for which around 250hp is the practical limit that it can handle.

This is why most high power cars S600, M5, lambos, porsches most AMG models until recent only came with RWD. Nowadays they are employing fancy torque vectoring systems similar to Nissan GTRs and Acura SH-AWD.

For your average 200-300hp sedan I would steer away from AWD, unless you do a lot of winter driving. AWD models are often heavier and slower, use more gas, require more maintenance, and have higher ground clearance which results in large tire gaps and overall SUVish stance.

Quadro

Yeah and once one of your rear wheels start slipping in an RWD car the other wheel will get no more torque either so what's your point? If your point is that in AWD with open diff one wheel loosing traction is enough to get you stranded then I'll give this to you but I may also point out that RWD can't event sent the torque to the front wheels to begin with and if you have not enough traction under your rear wheels then you're stuck for good too so which one would you rather take?

The problem you're describing have nothing to do directly with AWD but rather a behavior you get with open differential. If you read a coupe pages back you'll see a link comparing different AWD implementations and that's exactly why full-time 4WD with Torsen ranks so high because it can actually sent more torque to the wheels which have traction when other wheels are slipping. The problem of some wheels having no traction at all is solved by having locking differentials and/or various electronic systems applying brakes to the slipping wheels.

Of course you can take the worst/lamest AWD implementations out there and make example out of these all day long all you want but their weaknesses have nothing to do with AWD per se, just particular AWD implementation.

Whitigir

I hear the best AWD is Acura SH-AWD...after that is Symetrical Subaru ?

I hear Lexus AWD is like almost no comparision to any other brands on the market

Och

iTrader: (3)

It's not about getting you stranded, but front wheels lose traction easier because they are doing double duty. Also, high power cars often run staggered setups - you just can't putt massive, grippy wheels upfront. This is why you don't want traditional AWD setup in a high performance oriented car, as the front wheels will just keep losing traction prematurely under throttle.


Torsen LSD has been around for decades, and until recent it was pretty much the standard for AWD systems with LSD. The problem is, it can only send so much more torque to the wheels that have tractions vs the slipping wheels. i think its around 30% of so. With high power cars thats not nearly enough, and LSD being a purely mechanical system still does not deal with adverse effects of slipping wheels - so you get all the beauties of FWD such as understeer, torque steer, premature tire wear, etc.

Well, many manufacturers don't even have any description of their AWD systems on their website or service manuals. With Lexus sedans in particular, there's no information to be found oh how the system works. For all you know, it might very well be a pretty lame implementation.

Just to be very clear, I have no problem with modern torque vectoring AWD systems, and I am a big fan of Acura's SH-AWD. It is an advanced, intelligent system that provides for better handling, better traction in adverse weather, and doubles down as very capable vehicle stability control system.

Quadro

I see what you saying but I think it can go either way. For example, when you're stuck, having the ability to position the front wheels under different angle can give you a benefit because wheels can find more traction that way and get you out while your rear wheels are fixed and there is nothing you can do. The bottom line is you can keep imagining infinite number of conditions under which one system performs better compared to another but proper AWD/4WD system will beat any of them.

And I do agree that that is the main issue. People see the word AWD without realizing that there are many ways the system can be implemented. In sedans and even some SUVs (AWD RX) the implementation is pretty lame and underwhelming indeed but that's also why people shouldn't put stigma on all AWD just because they drove an AWD RX and discovered that it's primarily an FWD car until front wheel slip is detected at which point it might be already too late.

But the cars that Lexus says can go off-road, namely GX and LX, have very strong implementation with full-time 4WD, locking Torsen centre differential and A-TRAC to brake wheels which completely lost traction to keep you going even when some wheels are hanging in the air. That system is head and shoulders above compared to what they have in, say, Lexus RX but GX/LX cost different money too.

Och

iTrader: (3)

I wasn't arguing that part, there's no argument that in bad weather AWD system will outperform RWD. I was strictly talking about dry pavement traction in high power vehicles.


Well, its also important to remember that trucks with part time 4WD systems, while very capable require special knowledge and some experience from the driver. Have an unfamiliar driver activate center lock and drive at highway speeds on pavement, and mechanical damage will occur, or worse yet it can result in a spinout around a sharp curve and cause an accident.

Quadro

True but GX/LX don't have that problem, they are designed to be in 4WD all the time (hence they are full-time 4WD) including highway speeds on pavement. 4WD in GX/LX can not be disabled so there is nothing to enable - they don't add any additional complexity for the driver.

yowps3

AWD improves weight distribution on otherwise FWD application

Infra

iTrader: (1)

The mass of a vehicle has no effect on it's ability to stop, pretty much. The increase in momentum is offset by an increase in the friction force.

Steering is a different issue because only the traction on the front axle matters, so the change in weight distribution matters more than the magnitude increase in weight.

It's pretty common for trucks to haul around ballast in their beds in the winter simply because the additional mass significantly increases traction on the rear wheels in ALL aspects of driving (both more mass for cornering & more rear-biased mass for acceleration).

Infra

iTrader: (1)

Nearly every full-time AWD car with an open differential in the middle has EDL (brakes) to increase the torque required to rotate slipping wheels, allowing torque to be sent to the wheels with grip. The same occurs with a Torsen. Newer diffs like Audi's crown gear have a clutch pack that will automatically send torque front/rear without needing EDL.

There is not a case where a modern AWD system will have one axle slip and be unable to move. TC is required in every car sold today, which will allow the rear wheels to receive torque.

Och

iTrader: (3)

Yes, but don't forget that while stability control systems can simulate LSD effect by applying brakes to slipping wheels, they also severely cut throttle when slip occurs. That's not what you want for high performance driving.

SW17LS

I think it obviously depends a lot on which Lexus we're talking about.

My GS is AWD. I chose AWD because...I didn't have a choice. in my region RWD in any Lexus that offers AWD is a special order. So, no RWD IS, GS or LS. Had I had a choice I would have chosen RWD.

The reason for that is what others have mentioned here, RWD offers the best driving feel in general. Obviously in the snow thats not the case, but I have the Jeep to drive in the snow so I don't need the Lexus for that. Plus, AWD costs more, reduces performance...for some ability I don't need. Moot point since Lexus' allocation plan made the decision for me. Could have gotten a RWD 5 Series or E Class easily. A6 I would take the AWD over the FWD, obviously. My Jeep is QTI which is just their basic AWD system with no low range or any driver selectable settings. Oddly enough driving both the Jeep and the GS around on a normal day, the Jeep feels more RWD-like than the Lexus. You can definitely feel that the Jeep goes 100% torque to the rear while the Lexus only goes 70%.

Now, If I only had one car I'd feel differently. I've had RWD cars in the snow, without winter tires they are a handful and we don't get enough snow and our temps are not cold enough to warrant the expense and hassle of winter tires.

When it comes to SUVs, I simply do not understand why someone would buy a 2WD SUV. My cousin lived in FL when he bought his Jeep and its 2WD...because that was the low hanging fruit down there. Tried to talk him into getting 4WD. Now he's moved back to WV and he got his 2WD (FWD even worse) Jeep stuck in a ditch. I don't understand buying an SUV unless you get AWD/4WD....

JDR76

I'm in a similar situation where the availability of 2WD models in my area is severely limited. With that said, I would have opted for AWD in my IS350 regardless, and here are my reasons:

- Prompt acceleration in the rain. I live in a wet and hilly climate. I've owned many rear and front wheel drive cars. Go into downtown Seattle, and sit at a stop light on a steep up hill in the rain. The light turns green and in a 2WD car your tires will spin as you get started. Also, one of the turns out of my neighborhood requires a hard right hand turn onto a 50 mph highway. Try to pull out there too quickly, and again, you'll spin your tires.

- Snow. We do not get a lot of snow here, luckily. But my office building is at the bottom of a 1 mile long 18% grade. Even a dusting of snow and people get stuck. I don't want to be one of those people. We also take fairly frequent trips to the mountains and across the local mountain pass in the winter, and that extra traction really does come in handy on less traveled side streets.

Agree or disagree, but those are my reasons. The tradeoffs I see are the initial up front cost of the AWD in the purchase price, an EPA 1 mpg combined hit, and, depending upon the publication and test results, around .1 second additional time to 60 mph. For all the confidence that gives me, I can live with it.

Now my wife's car is an AWD RX350. For many of the same reasons above, but also because like SW13GS, I cannot find it in myself to purchase a 2WD SUV.