vlad_a

Andy, VDIM is just that good. With FWD bias, traction control keeps thing contained all the time. I believe lights flash only under harsh interference.

A few weeks ago, I was driving the RX in a heavy snow storm. It was pretty uneventful, particularly since I'm running winter tires on both of my cars now.
I then had to pick up my IS from the parking lot at work. I jumped into the IS, turned off traction control (as I usually do) and gave it gas. That caught me by surprise. By that time, I was used to RX just going going about its business. I had to readjust at how "loose" the car was without VDIM engaged and AWD. A few doughnuts in the parking lot accomplished this task.

vlad_a

Got plenty of snow and unplowed roads this AM. VDIM went about its business, fully transparent, and w/o any indication of its work, other than keeping the vehicle going where intended. It starts beeping and flashing only if it is unable to fulfill driver requests.

abscam

Bit of a delay in my question, but relatively new 2011 RX450H driver, living in the SF Bay Area. Heading to Truckee in the Winter in the 450H? Can I do it? What tires would you recommend, or should I skip it and just take the Merc GL450 w/ obviously better 4WD options?

I'm in the market for tires anyway, mainly highway commute, but would want M+S just in case I get up into Truckee in some snow. Thanks for the input.

kitlz

Welcome to CL, abscam. I'd suggest taking a look at the 3RX tire thread here for recommendations from fellow members. Or check out reviews on CL sponsor Tire Rack. Between the two you can find some great tire recommendations.

falconer

Abscam,
Regardless of the tires you choose, when traveling in the Sierras in the winter you will still need to carry chains to be legal, FYI.

oohpapi44

iTrader: (1)

Really depends on what you plan to do in the snow as well. Commute = RX450. Real fun in the snow = GL450

NateJG

I noticed that, in my 2013 450h AWD, Snow Mode kept the rear motor engaged until approximately 37* MPH - and for me, living on a lake and forced to navigate 25 MPH winding roads for about 4 miles as I leave/arrive, I enjoy having AWD engaged while at 25 MPH.

I was (and still am) a little concerned that the Computer Nanny might override my wishes if I ever have the misfortune of running off the road and wanting to simply "GO GO GO" out of trouble; however, here in Michigan's worst winter in a generation this past winter - I never got anywhere close to stuck!

The street just off my driveway is normally not a choice in winter/snow; however I continuously "tested" the car by stopping mid way up the incline on ice/snow and then starting up the hill.

While other Hybrid owners may agree with me that a push on the accelerator is but a mere request (as opposed to an order), the car ALWAYS went slowly up with the hill with barely perceptible wheel spin - regardless of how hard I tromped on the accelerator.

I even stopped many times while descending it and other normally bad choices for road inclines - and stepped on the "request pedal" in reverse - only to have it slowly, but effectively, back up the incline - with little perceptible wheel spin.

My RXh was my first choice over the Dodge 4x4 Ram this past year in snow (except for when I didn't want to get it dirty).

When not in Snow Mode, I found the front wheels more prone to slippage - however, the traction control did effectively take over. Snow Mode was more pleasant a driving experience.

I am very impressed.

(26 left)

*Originally posted as 27 MPH. We had our first real snow of this year's season last week, and I again "tested" the car on slippery slopes. It's simply amazing. Backing up slopes; Driving up slopes; Doesn't seem to matter which. It just goes with virtually no wheel spin (although speed is minimal when very slippery) in Snow Mode.

MellonC00

sorry to bring up an old thread...... I realize the snow mode engages the rear motor a little longer as Nate states above. But I'm wondering if the car retards the timing or reduces system power in general making the car feel more lethargic to counter any sudden jolt of acceleration/wheelspin.

NateJG

I doubt that timing is an issue, since thrust is largely electric motor related - and my experience (I live in rural Michigan) on ice and snow has been that it's virtually impossible for me to spin the tires when in snow mode.

As an example, the roadway out of my neighborhood is a 12.3% grade (7 degrees) - and most two-wheel-drive cars have trouble ascending the road in snow - and many AWD cars have trouble on packed snow.

I have tested my '13 RXh AWD many times on that grade by stopping midway and starting or backing up the incline in both the regular, and snow modes - with throttle pedal position of little significance - meaning: I can slowly hit the throttle, or modestly hit the throttle, or floor the throttle with the same result - the wheels slowly turn (not spin wildly) and the car moves up the hill.

It's the most amazing thing I've driven in my 51 years of Michigan driving.

I have considered and even worried about whether or not the electro-nannies would prevent me from "powering" through snow if I were to find myself suddenly off road (by shutting off the power to the wheels like I've experienced in my other Traction Control Equiped vehicles); however, and fortunately, my car has never left the roadway nor have I found myself in snow deep enough to cause trouble.

I find that, while driving in Snow Mode, the front wheels stay planted better than not in Snow Mode -- likely due to the computer not having to wait until there's a slip of the front wheels before supplementing the forward motion with the rear motor.

I have not ever read any review from any owner with an RXh FWD to see how it functions in Snow Mode (Question: is there a Snow Mode in the FWD RXh?).

As for the issue of whether or not it feels more lethargic - I'd have to say that, perhaps, it is on the same level as is the ECO mode -- which I find perfectly acceptable for winter driving - but a bit less than I prefer for day to day traffic/driving (I spend approximately 75% of my driving time in regular mode, less than 5% in Sport, and therefore a bit more than 20% in ECO - depending upon my mood, traffic, and need for speed variation).

Helpful?

Update ten minutes later: I went and re-read my 2014 post; and apologize for largely repeating what I said then (at least my story hasn't changed much, grin).

MellonC00

This is very important info. Knowing this, I'll try to take the car up to the mountains this winter for ski trips. Thank you for the detailed explanation.

MellonC00

Question. Is the front or rear transaxle considered e-limited slip differential? Or are they considered open?

vlad_a

Both are open and VDIM does a poor job simulating LSD functionality for front axle under full throttle, resulting in torque-steer (not specific to driving conditions).
Center diff, or lack there of, is an interesting one, as it is all electrons. It very well could have been a "locking" type, but the rear motor is too weak for it to be effective.

F250

I can verify that my 2010 FWD RX450h does in fact have Snow Mode. I cannot, however, speak to its performance difference between ON or OFF settings.

MellonC00

this is something I'm not very good with. Why don't cars just come with LSDs? If there a severe weight penalty for LSD vs. open?

vlad_a

There are too many complexities to deal with. Differentials exist for a reason - if all wheels turn at the same speed, vehicle will only be able to go straight.
If LSD is too restrictive, it will create forces that attempt to send the car into a skid.
There are may different LSD implementations. Some wear out too fast, others need extra maintenance.
Torsen is the most common and robust, but it starts acting just like an open diff if one of wheels has zero traction.
Bottom line, all of the above incur extra cost that most customers would not be willing to foot.

Typical Lexus customer will think LSD has little to do with traction.