Last post on Jul 06, 2013 at 3:20 AM
You are in the Toyota 4Runner
What is this discussion about?
Toyota 4Runner, SUV
Jul 02, 2004 (4:39 pm)
Prior to owning my '03, AWD, V8 4Runner Limited with X-REAS, I put 50,000 miles on a 2002 4WD Explorer XLT (and before that, almost as many miles on a girlfriend's '97 Explorer Sport). In my experience, the Explorers (especially the '97) were far more top-heavy and prone to roll and pitch. When driving the Fords, if I started (for example) into a freeway or highway curve going just a little too fast, I would immediately feel the vehicle beginning to teeter and understeer. (Those of you who're familiar with this teetering sensation know that it's not pleasant!)
By contrast, my X-REAS, AWD 4Runner negotiates the same curves (at the same or even higher speeds) with tremendous stability, surefootedness, and without any teetering or impending roll sensations whatsoever. Now mind you, I'm not about the business of trying to see just how far I can push the 4Runner, because it certainly has its limits. I'm merely saying that compared with the Fords; the X-REAS, AWD 4Runner is the most stable, well-mannered, maneuverable, safe, and above all, FORGIVING sport utility vehicle I've had the pleasure of driving (and I've put over 19,000 miles on mine so far).
Quoting Toyota's literature: "X-REAS links each of the vehicle's shocks to their diagonal counterpart via a gas/hydraulic chamber-- front-left to rear-right, and front-right to rear-left. During cornering or traveling on a bumpy surface, the gas/hydraulic chamber acts like a bank, 'borrowing' fluid from the cross-linked shock bearing the least amount of force, and 'loaning' it to the shock sustaining the greatest amount of force. This helps the 4Runner's wheels maintain contact with the driving surface and helps lessen vehicle body roll and pitch..."
Let's suppose you're heading into a rightward highway curve just a little too fast or "hot" in a top-heavy, lesser SUV that lacks X-REAS (such as the new Explorers). As you enter the curve, the lesser vehicle will begin to teeter to the left, and you will feel the vehicle's top-heavy body beginning to roll to the left. You will also feel it starting to understeer and wanting to travel to the left, possibly running off the road unless the appropriate corrective actions are taken. At this point, an inexperienced SUV driver may try to OVERSTEER the vehicle back to the RIGHT (back into the curve), and this may very well cause the vehicle to completely roll over. (In my experience, the most appropriate corrective action in this situation would be to first begin gently but assertively applying smooth and steady braking in order to slow the vehicle fairly quickly, thus quickly bleeding off the offending angular momentum The more the vehicle is slowed down, the more it will permit and tolerate being steered back to the right.)
As the above rollover scenario unfolds in your mind, note that as the lesser SUV begins to teeter and roll to the left, the shocks on the same side of the vehicle are becoming evermore compressed and overloaded with stress and weight. Meanwhile, the shocks on the right-side of the vehicle are becoming ever more extended and unloaded as the right side of the vehicle begins to lift up in the course of the vehicle's leftward teeter and roll. In this situation, as the right-side shocks decompress and extend themselves, they may tend to further TIP the vehicle's precarious attitude towards a leftward rollover.
Next, consider this same scenario with the X-REAS *safety* technology in place. Here, the left-side X-REAS shocks would progressively stiffen as the X-REAS system dynamically strives to correct these force imbalences by diagonally cross-transferring hydraulic/gas pressure into the left-side shocks, thus directly COUNTERING the leftward rollover forces and angular momentum. At the same time, X-REAS is temporarily transferring hydraulic/gas pressure AWAY from the right-side shocks, thus reducing their tendency to "bounce" the vehicle back towards the leftward tipping if/when the vehicle's body should roll back to the right in the course of corrective actions on the part of the driver.
In my opinion, X-REAS works as claimed, and then some. Indeed, I do a great deal of freeway driving, and I've had several close calls in my 4Runner, in which someone abruptly pulled out closely in front of me, right in my path. At these times, I've instinctively taken emergency evasive actions, and thankfully I've not been involved in any accidents, thanks in large measure to the truly remarkable stability of my X-REAS, AWD 4Runner. Indeed, this magnificent vehicle often feels like it's Michelin Cross Terrains are "glued" to the road, and I've simply never driven another SUV with this degree of performance.
That said, when we're suddenly faced with this type of split-second hazard, I don't care how good a driver you are-- your first instinct will likely be to (1) abruptly jerk the wheel in an effort to steer out of the impending collision, and (2) aggressively apply the brakes. (In fact, if we can train ourselves to do so, I believe that within the world of "microseconds", the very first countermeasure should be assertive BRAKING, followed a "microsecond" later by reasonable attempts at evasive steering maneuvers.) At any rate, any time you jerk the wheel of an SUV in an effort to avoid calamity, you risk rolling the vehicle and possibly killing yourself and others. But as I've opined above, it is my humble opinion that the X-REAS equipped, AWD 4Runner is the most FORGIVING, SAFE, NIMBLE, MANEUVERABLE, SUREFOOTED and ROADWORTHY truck I've ever had the pleasure of driving.
X-REAS is our good friend. While its many virtues may not often be so "obvious" in the course of more mundane day-to-day driving... those same virtues, especially the enormous SAFETY value of X-REAS, should become quite evident if you ever need to call upon it. In my opinion, those who would claim that X-REAS is hype, don't yet really know what they're talking about. If your 4Runner has X-REAS and you're not yet "impressed" by it, perhaps you have yet to encounter (or to fully recognize and appreciate) the many moment-to-moment situations where X-REAS is actually at work, unobtrusively and adeptly assisting you, the driver.
I rest my case.
Jul 02, 2004 (8:37 pm)
Or it could be that a 4Runner on Michelins simply is a much better handling SUV that a Ford Explorer. X-REAS may have very little to do with it.
#10009 of 11429 Re: 10004 of 10008 RE: V6 or V8
Jul 02, 2004 (9:47 pm)
Actually, the towing capacity of the V-6 is rated at 5,000 pounds (weight-carrying). As a side note, I have a 2004 V-6 SR5 2WD - I've had it since January, and have 7,260 miles on it - and I am plenty/very happy with it; zero problems to date. /Ron
#10010 of 11429 RE: by markjenn
Jul 03, 2004 (3:47 am)
Tires has almost nothing to do with reducing body roll.
A few months ago, MSNBC did a special about SUVs and their propensity to roll over. Their was a test (performed by NHTSA, I believe) that showed both a 4Runner with and without X-REAS. The S-REAS equipped 4Runner performed much better at the slalom and in the emergency lane change maneuver.
There was also a video link showing the X-REAS in action on the MSNBC site, but unfortunately, the article and video are no longer available.
The X-REAS is not just for show. There is a clear demonstable advantage in having it.
#10011 of 11429 RE: Re: 10004 of 10008 RE: V6 or V8 by hlron
Jul 03, 2004 (3:48 am)
You are correct. The V6 can tow 5000 lbs. I must have made a typo
#10012 of 11429 RE: by markjenn [alfster1 #10010]
Jul 03, 2004 (7:32 am)
"Tires has almost nothing to do with reducing body roll."
I whole heartily disagree with you on that statement, it is part of of the total handling makeup. You get some tires with weak sidewalls, and/or improperly inflated and you will definitely experience more body roll in just about any vehicle. Not to mention cornering and just about any kind of road handling manners can be improved with better threads on the ground.
I do like and believe in the X-REAS setup, and plan to get it on my 4R.
#10013 of 11429 4Runner on NBC and anti-roll
Jul 03, 2004 (10:09 am)
IIRC, the differences in roll behavior in the different tests were due to VSC, not X-Reas. However I think that X-Reas would indeed help.
Also, I think the biggest roll danger isn't from the first quick or hard turn you make. It's from the compensating turn you make the other way after you've avoided what you were trying to avoid (or the turn you make to straighten out after you've turned too far). The problem is is the momentum in the body roll as it's trying to roll back upright after being disturbed by the first hard turn. During the second turn it adds to the tendency of the vehicle to roll. VSC and X-Reas, I think, tend to prevent this, though they do it in different ways. VSC probably helps control turning, while X-Reas lessens body roll.
If you want to understand this better, just imagine accidently drifting off of the right side of the pavement due to falling asleep, inattention, etc. When the wheels get off the pavement you jerk the wheel hard/fast back to the left to get back on the road. Then you find you've over-corrected and may be in danger of veering into the oncoming lane or going off the other edge of the road. You yank the wheel hard/fast back to the right. Imagine the side forces and body roll sequence in this case and you'll see what I mean.
#10014 of 11429 X-REAS +/- VSC, etc.
Jul 03, 2004 (4:44 pm)
Correct me if I'm wrong, but doesn't an alarm sound in the cabin (accompanied by the VSC icon illuminating) when the VSC and/or TC kicks in? So far, during my previous evasive maneuvers on dry pavement, I've not yet heard any alarm, which leads me to think that at least in those particular situations, X-REAS was working without the additional aid of VSC(?).
Regarding the role that tires play in this debate, I would mention that my 2002 Explorer was also equipped with Michelin Cross Terrains (my favorite tires). Also, I would think that the past issues with certain Firestone SUV tires would seem to suggest that tires which are over-inflated, oversized, or prone to catastrophic failure, are likely to be important contributing factors in some rollover accidents.
Corancher raises some interesting points regarding the likely succession of steering countermeasures, along with their possible consequences. To this I would say that in my previously posted scenario, I actually addressed this to a limited extent when I wrote: "At the same time, X-REAS is temporarily transferring hydraulic/gas pressure AWAY from the right-side shocks, thus reducing their tendency to "bounce" the vehicle back towards the leftward tipping if/when the vehicle's body should roll back to the right in the course of corrective actions on the part of the driver...."
I believe a key point here would be that evasive steering maneuvers (or other sudden perturbations) in an SUV may be likely to send the vehicle into an "OSCILLATING" pattern of unwanted motion, including various combinations of roll and counter-roll (rotation about an axis); pitch (up-down); and yaw (side to side). Once these oscillating movements are set in motion, the vehicle is, of course, in an unstable and precarious attitude.
Aside from certain driving countermeasures (which may be unreliable), I believe that X-REAS and the new 4Runner's other on-board safety systems (e.g., VSC and TC) greatly increase the chances for a safe and successful recovery. Systems such as X-REAS (and VSC/TC) serve to not only DAMPEN and quell these unstable oscillations and assist in bringing the vehicle back to a safer attitude; they likely also help to buffer, "TRIM", and COMPENSATE for many over-exuberant (or ill advised) inputs from the driver. In addition, I'm inclined to believe that 4Runners additionally equipped with AWD may be even more capable of a safe recovery, even on dry pavement.
In my opinion, herein rests the true ingenuity and technological prowess of the new 4Runners, especially when more fully equipped. Its advanced on-board safety systems are in some ways analogous to those in the world's safest aircraft. Indeed, among SUVs, the new 4Runners (and Lexus siblings) are without peers.
#10016 of 11429 Question for stove1
Jul 03, 2004 (8:36 pm)
Stove1, could you elaborate on your suggestion to wait for the '05
V-8 with VTEC.