Fwd Vs. Awd

[Bourbonjim]

I am preparing to purchase an RX for my wife, and am debating the merits of FWD vs. AWD. We live in Southern Indiana where we get maybe 12 in. or so of snow per year. I drive an ES300 and have never had the first problem. What are your opinions, experiences, or preferences.

Thanks,

Bourbonjim

[wwest]

First, the RX300 is not really AWD since they are front torque biased by about a 95/5 F/R ratio in normal use. If a circumstance of virtually continuous slippage (something on the order of tens of seconds) of the front driven wheels happens to occur then the VC will tighten up to about a 75/25 F/R ratio.

On 01 and later models, at least until the 04 MY, VSC/Trac became standard and thereby the "predominantly driven" front wheels can NEVER endure a continuous slippage condition since the brakes are virtually instantly applied to any slipping wheel and the engine is automatically dethrottled (to prevent brake overheating and rotor warpage) if the condition persists.

When the 04 model came out Lexus acknowledged that VSC/Trac had made the VC used in previous models useless and dropped its use altogether. The 04 model uses a simple open type center differential with the brakes used exclusively for torque apportionment. The 04 also uses a more disparate F/R final drive ratio seemingly making the F/R torque distribution closer to 98/2.

The bottom line to all that is the FWD with VSC/Trac will undoubtedly give you just as good adverse roadbed traction as would the AWD version.

But if you really want to find an SUV with excellent overall performance in adverse roadbed conditions then have a look at something that is predominantly RWD biased and one in which you start out using rear snowchains and then install front snowchains only in extreme circumstances.

But there is something else to remember. They is NO SUV, nor any regular passenger vehicle, that will reliably get up and go in the kind of wintertime weather we have had here in Seattle three times in the past 14 years absent the use of studded tires or snowchains.

If your travel countryside is flat then maybe...

During the wintertime there is always a set of snowchains stowed in the back of my 01 AWD RX. I used them the first time about a month ago now and they paid for themselves.

[lodown]

verry informitave i thought this rx300 didnt feal like my 4w drive yukon

[tds]

Here we go again :)

I live north of Toronto in Canada and we get a lot of snow. I installed 4 snow tires on my 2001 RX300 AWD and the winter performance is simply outstanding. I never get stuck and my traction control rarely comes on.

When compared to the winter performance of my rear drive 91 LS400 (again with 4 winter tires) I have around 1000 percent more traction (my guestimate :)

Remember that the AWD is used not only for deep snow, but also for ice and extremely slippery conditions. Because it is AWD the vehicle is balanced in extremely slippery situations, and balanced means stable and less likely to skid out.

Regardless of any of this remember that you cannot violate the laws of physics regardless of how many wheels you have driven. This is why it is usually the 4WD/AWD vehicles who are first in the ditch every winter. They have no clue how slippery it really is when they start out and they tend to overdrive the vehicle for existing conditions. They find this out when they try and steer around a curve or brake to a stop...they can accelerate better than a 2WD vehicle, but they cannot steer or stop any better (i.e. AWD/4WD is out of the equation for stopping and steering).

The long and short of it is that Lexus have done a great job with their AWD RX300. I highly recommend the AWD version even though the gas mileage is a little bit less and the maintenance is a little bit more.

[wwest]

"AWD/4WD is out of the equation for stopping and steering..."

NOT!

When attempting to change direction on a slippery surface with FWD or front torque biased AWD the engine drive or lag torque will often interfere.

Toyota has already wised up and realized the serious nature of 4WD during braking and stopping or slowing quickly. Their newest 4WD system cannot be activated unless the transmission is in first gear and the "transfer case" is in low range.

Before abandoning FWD alltogether Cadillac was using an over-running clutch within the transmission so the front "driven" wheels didn't reflect the engine lag torque to the roadbed.

And now most modern day FWD and front biased AWD vehicles use automatic transmissions that shift upwards, or maybe even into neutral, during any coasting, slowing or stopping event, Highlander and RX included, to help avoid loss of control on adverse roadbed surfaces.