Mr Johnson

Thwak: Was that a bitslap?!? :eek:

Sorry bit, I'm afraid wwest is correct. A LSD will help in any condition where one wheel has more traction than another. That's the beauty of it, one side slips causing the other side to start getting power.

wwest: There are two problems with a TRAC only solution in my mind. First if it only uses the brakes a TRAC system can be overpowered by the engine (the equivalent of a brake torque lauch at the track). The brakes won't hold the car and brakes overheat. If you have both brakes and throttle control then the system will dramatically reduce power but won't bring it right back on. Ever make a right turn in front of traffic with the TRAC on, punch it and watch as the TRAC cuts the power and the traffic from behind gets closer and closer?!? :eek: I have and it's not pretty. The TRAC system doesn't give you power back until it feels it's "safe" to do so. I'd rather let my foot and a LSD do the deciding.

This leads me to my biggest problem with the system. It doesn't add anything but rather takes it away. Just like TRAC vs AWD you don't have extra traction you just get a brake and reduced engine power to keep you on the road. That's why a lot of the "baby" SUVs can't navigate various off-road courses that "real" 4WD or AWD system SUVs can. Now for 90-95% of the driving done a TRAC system is cheap and works wonders (which is why many automakers used them). But if you are after perfomance you really *need* a LSD. That's why you'll get one, probably in concert with a TRAC system, in everything from Vettes, Porsches, BMWs and AMG Mercedes. There's nothing like being able to put the extra power down and then have the TRAC/VSC system for whatever backup you might want.

People who drive with me for the first time usually ask what that VSC off light on my dash means! It means watch out for the rear-end sliding....

gwu128: I have two similar questions. Wet weather with wide tires != good time. Did you have the TRAC on? You need to be careful, especially with a TC, in the wet. I am bummed if in fact the S03 don't work that well in the wet as those are the tires I was going to use when I get my new wheels.

Peter

RON430

LSD, VSC, TC, and a bunch more abbreviations. LSD works to transfer some amount of torque to the wheel that still has some traction (if I remember right, street cars have somewhere between 25 and 40% transfer). Assuming the wheel that is not spinning has much more traction. If you think LSD means never breaking traction, you are very wrong. In low traction situations you can get LSDs not knowing whether to lockup or go blind as it transfers back and forth alternately breaking both tires loose. Listen to bitkahuna, 300 hp, TC, 275 tires, and a WET road surface make life interesting. Before investing in additional fancy hardware, a driving course with some wet skidpad time might help. To figure you will always be able to nail a GS4, regardless of road conditions, and maintain traction, is just asking for the impossible.

Now for the stupid human tricks. This issue got me interested in the fancy electronics our GS comes with. On the way home tonight, I had a driving rainstorm to contend with. I have a 2k1 GS430 with stock 225/55-16 tires (Michelin) and only bilsteins added on (for now). I had three lanes with myself in the middle lane and no one around. VSC "on". From a dead stop - wide open throttle - shaking as I assume the VSC was cycling. Car was definitely not happy but accelerated away (slowly) from the stop in a straight line. Wipers on maximum. Next test was two accelerations one from about 20 and one from about 40 to full throttle. VSC light blinked on, slight vibration but steady acceleration and absolutely no sideways movement of the front or rear end. Under all acceleration, the GS stayed absolutely arrow straight and telegraphed its extreme displeasure with my stupid human trick. Backed out of the throttle fairly quickly, it was obvious that the car was not happy about what I was doing but at no time did either end step out. Impressive.

gwu128 - Either something is not right in your VSC or the combination of the tires/TC/300hp/wet road is just too much. Any of you in the San Jose area should be able to vouch for the cell that went through about 7pm tonight. It was pouring as heavy as I have seen so far this year. LSD is very worthwhile but the modern electronics are amazing. Being an old fart (Mean Gene,you out there) I haven't been a big fan of the electronic control but I have turned into a believer, at least in cruddy weather. It certainly is possible to mod the car to defeat the programming but if you don't drive in perfect weather all the time and maybe have a wife to think about, you should think carefully about what you are doing. At least in stock form you have to be very weakly connected to your driving to get in trouble with the VSC in the wet. As for ice - you're on your own.

wwest

You just described, almost exactly, one of my early complaints to Lexus back in 92 when I had just bought my 92 LS400. Pulling out of a street into a LEFT turn, with large white, slippery, crosswalk striping, the trac would engage and if I didn't get off the gas right away it would dethrottle the engine. Hell of a thing to have happen if you have timed the approaching traffic a little tightly.

Now you set there in front of on-rushing traffic with NO ENGINE!

In the 92 the simple answer was to disconnect the downstream ECU controlled throttle, a little rough on brakes, but those are cheap and easy to replace.

I now have a 2000 GS300 and it has been my impression that Lexus has further delayed the onset of the de-throttling action so that if TRAC is only "on" briefly it doesn't activate. Now define briefly, right.

But I think one of the nice things about TRAC itsself (braking only)is its very quick "onset", it seems to me that the wheel only has to "think" about spinning (1/2 turn?) and trac activates instantly but only momentarily, before any real rotational momentum is built.

"Doesn't add anything..."

Several people in the racing venue have told me the opposite. Apparently braking the wheel to keep it from spinning out of control, and traction, is giving them better track times.

TRAC as LSD for SUVs...

Tell me about it!

I bought my first SUV in 87, a 1985 Jeep Cherokee limited with a Chevy V6 engine. Now I do not wish to discuss off-road use of an SUV in any context. I live here in the Seattle area and apparently what we often have to deal with on-road is more like others around the country deal with off-road.

I traded up to a 92 Jeep Cherokee in 92. The Jeeps served me very well. I was always puzzled as to why the full-time 4WD never actually did me any good, if the going got slippery I always had to resort to part-time mode, and on numerous occassions 4 tire chains. Generally the only time these vehicles went off-road, into the ditch or the median, was to get around stalled traffic on the roadbed. And of course your typical ski area parking lot.

In late 99 I traded up to a 2000 RX300 AWD. I neevr had a chance to really test it, but its torque steer was really off-putting and my sense was the rear wheels weren't really doing their share. So I traded up to the 2001 RX300 AWD to get VSC, TRAC, and HID.

I have analized the RXes AWD setup til the cows came home and I still can't make sense of it. Basically it appears to be three open differentials with a VC to "lock" the center differential if there is a disparate rotational rate F/R or vice versa. But every shade-tree test I can devise indicates that the RX300 is always predominantly FWD.

Now when I bought the MY2000 RX my saleman of ten years told me it was FWD biased, 70/30, but would get to 50/50 if the front wheels began to slip.

Everything I have seen published by Lexus since says it is normally 50/50 and it will automatically route a higher percetage of torque to the wheels with grip.

It doesn't. And because it appears to me that it doesn't because I have come to believe that the VC isn't fully "charged". But I still can't find an explanation for why the front wheels will "drive" with the rears lifted and spinning freely, and in the reverse configuration the rears don't seem to "drive" even with the engine RPM at 2000. Didn't dare go much above idle with the fronts threatening to jump the chocks at any moment.

The final drive ratio to the front is greater, 3.12 (approx) vs 2.93 (approx) But I don't see how that would affect the torque distribution. To me it even seems it would most favor more torque to the rear.

But you certainly seem to be correct about TRAC being used to sunstitute for LSD in an SUV. MY 2001 RX has exhibited what I attribute as VSC activity on several occassions, but seemingly has NEVER activared the TRAC. And if I am right and the AWD RX is always predominantly FWD biased I can certainly understand that applying TRAC, braking, the front wheels if they begin to slip could be hazardous.

The Jeeps were bad enough at knuckle busting without a front axle LSD, I can only imagine what TRAC would do to one's knuckles if applied strenuosuly to one front "spinning" wheel.

I have just posted my weekend episode with my AWD Aerostar vs an HL and and an RX AWD and a new 4runner. You can find them easy enough if you want.

wwest

Terrific post, right on!

RON430

wwest - You know I have been having a hard time figuring out the systems on the GS (the manuals seem to be written by someone who follows the riddle wrapped in an enigma wrapped in a.....) but this issue on the VSC and LSD just caught my eye. Obviously the open differential is cheaper than an LSD but I am not sure, as I think you are pointing out, that it doesn't work better with VSC than an LSD. Doubtless they are refining the software every year. I am not sure that the issue is "Can Michael Schumacher drive a GS faster without the computer control" as much as it is "The average driver is far safer with these controls engaged than without". LSDs do bring downside like noise as the clutches bind and they have to be rebuilt because of those clutches. Don't figure the dual viscous coupling LSDs are showing up in road cars yet. And that amount of torque that transfers is a delicate issue. If you are dragging or stock car racing on an oval where you can use stagger to go around the corners then a locked LSD is great but you can tell who has one because they are the cars that can't make a U-turn. And anyone who thinks LSDs are bullet proof should have ridden with me in a 69 L88 corvette in Chicago thirty years ago in winter. I really am not sure how I did it.

I have to think about your comments on the RX, it is an interesting system. Fundamentally isn't the problem that the RX is not meant to be an off road AWD? It really is a FWD vehicle with some AWD capability but more for inclement weather rather than real rock pounding. Never got an RX but I can't figure out why it is one of the very few SUVs that I am comfortable in. With the popularity of those things you'd think the other guys would spend a little more time on the interior. Then again the other guys do road test on the Rubicon. I guess it is a trade off.

enginyr

If the wifey is driving it alot, I'd seriously concider removing the aftermarket Torque Converter. That high rpm engagement is vicious.

wwest

Happen to also have a 2001 911 AWD at:

http://www.hobbystage.net/porsche/whatever

Only 6k miles and I haven't been brave enough to take it out into the snow and ice yet, maybe never will. The PSM definitely works in my favor if I want to drive the car hard but not with my constant full attention. Many expert drivers have said the PSM is better and quicker reacting than themselves.

RX off-road.

As I already said, I never "play" in that venue. But in the many years I owned Jeeps I had more than enough opportunity to experience off-road like venues on-road. I live in the Seattle area, snow ski, and have relatives in Montana and on the dry side of the state, east of the cascades. Mountain passes are not an easy thing to overcome in the wintertime absent a serious type of AWD.

Additionally our area has had two serious snow storms in the past ten years, one in December of 90 and another just after Christmas in 95. When I say serious I mean the only way to travel for about a week was in a TRUE 4WD vehicle, with four tires chains if you wanted to travel in neighborhoods and not on the main, plowed, streets.

Seattle is something like I remember Memphis being, doesn't snow seriously often enough to justify buying the snow removal equipment. And so people simply stay at home fro the duration or own a SERIOUS AWD vehicle.

I'm beginning to suspect that the TRAC and VC versions of AWD are just simply not up to the task at hand, at least not here in my area.

Not sure many people know it but you CANNOT install chains on the rear of the RX, (is the HL the same way?) the coil springs are within less than a inch of the tire tread. The RX owners manual says install chains ONLY on the front but when I challenged Lexus about the extremely hazardous nature of that practice they backed down and said I should ONLY use snow tires all around.

RON430

wwest - Funny you should mention Memphis. As I recall they had a very religious view of snow. God put it there, let him get rid of it. Not that this has immediate importance but in your opinion does the RX meet its intended purpose of being better in slightly nasty weather than a simple FWD vehicle? I don't think anyone views it as a serious off roader but I am just curious how it does for the majority of cruddy weather.

wwest

In answering, I'm assuming you mean RX AWD vs FWD.

Any AWD, however lame, (why is it that the HL and the RX came immediately to mind when I say that?) will do better in "slightly nasty" conditions than a FWD. Actually, in MMHO, any RWD will be safer, overall, in "slightly nasty" conditions over a FWD.

But why, oh why, does this OFF-ROAD issue keep coming up?

In some parts of this country, and in many parts of the world, you absolutely don't need to go OFF-ROADING in order to truly NEED the FUNCTIONALITY of a REAL SUV !!!

I have come, am coming, to believe we need to create a new "class" designater, name. A predominantly FWD biased SUV (HL, RX, MDX, etc.) is nothing more that a different type of AWD minivan.

IMHO the BMW X5 3.0 absolutely personifies this new class.

Maybe we should follow BMW's lead and all start using SAV to indicate a vehicle class that is NOT off-road "worthy", but is up to the task at hand on the snow and ice covered roadbeds and mountain passes in the northern states in the wintertime.

What do YOU think?

RON430

wwest - Thanks for the reply. You have raised somewhat of a sore point for me. Thirty years or so ago (ugh) I did all my driving around the Chicago area in RWD cars, some with a lot of horsepower even for now. Seems like the only FWD cars back then were SAABs. I understand the technicalities of FWD but good grief, you would think that RWD is going to kill you if you get to nasty weather. Granted I may not have the reflexes I had back then but RWD can do quite nicely in dodgy situations if there is a driver at the wheel who is familiar with both the vehicle and the situations. Not trying to start a flame war on the advantages of FWD or AWD, which I acknowledge, but to hear some people they just assume you have to park a RWD car all winter. This sort of brings us back full circle. Expecting LSD or VSC or AWD to replace the driver is a fantasy. Putting down 300hp through a potentially higher lockup TC on wet pavement could be a prescription for disaster. I don't normally do potentially costly experiments like I did last night (especially with a GS430 with not quite 7K miles) but I thought I could handle it and low and behold, all the electronics provided a surprising degreee of stability. And, as I said, it was very plain that the car was not happy with what I was doing and I would have to have the reflexes of a house brick to push it further. Obviously vehicles like the RX and Subaru as well as the Audi's (I guess) are bringing the advantages of AWD to something other than rock pounders. But the fundamental remains that AWD is only of help accelerating and if you think that means you have traction and control under all circumstances and conditions, you are going to wind up very disappointed.

OFF ROAD - couldn't agree more. As we all know the vast majority of the SUVs never set foot off road and even if the vehicle is capable of it, I doubt most drivers are. The older I get the more respect I have for the people that are good at all types of automotive driving from off road to formula one to drag racing. All require a unique skill set that deserves some respect from us that aren't quite so gifted. I think my wife is on the fence on the SUV. She likes sitting up high (particulalry the RX) but comes from a long line of Jaguar ownership (E-types not the current flavor) and just doesn't like the handling with the center of gravity feeling like it is three feet above the roof. All sorts of people out here, that's what makes it a horse race.

wwest

Like the good doctor recently said, the better your RWD, FWD, AWD, 4WD, is, the deeper into the woods you can get before you get stuck!

Apologies to Mooretorque.

We currently have an 2001 AWD RX300 primarily becuase of my wife's preferences, sets up high, etc. I upgraded it to 17X8 wheels and +1 tires, Michelin CTs which required 1" wheel spacers in the rear to clear the suspension so I put them all around. Overall net is about a 3" wider stance, noticeably more stable than factory.. and better traction with the wider threads.

If the ML continues its rather dramatic improvements in relaibility year to year there's probably one of those in our near future.

If you're thinking of making your wife happier by buying her an SUV look at the ML first.

The RX has a few flaws, the AWD setup doesn't seem to be up to par with whats really needed for our "turf", the GPS Nav is a joke, useless is the best term, and the Lexus climate control system has had the same basic flaws since the beginning of the marque.

RON430

ML reliability glitches aren't exactly a well kept secret. Compared it at the SFO and SJ auto shows and the ML just left me unimpressed and the back seat was the most uncomfortable seat I experienced in an SUV. The RX is not only more comfortable but really has that completely finished feel to it. That is a somewhat uninformed opinion and, after all, I didn't buy either. But I was in line for a 500CL which never did come in but someone backed out of one so the dealer called me in to see if I wanted it. First time I got close and while nice it just didn't seem like I wanted to put out a hundred large for it so I backed out. Things are getting tougher, can't wait to see the new 7. I don't think I am going to like it either. Thank goodness for bargain buy GSs. Another senior moment, sometime a $50K car looks like a buy.

GS4Will

hey Ron,

for a bit more $$$(relatively speaking), do you think the cl55/s55 amg are worth the money..?

RON430

hey william - Why do you like to put me on the spot? I really don't know. When you get up to that rarefied atmosphere a bunch of life priorities take hold. I have seen a couple of s55's running around up here and no CL55's. My flying toy was going through the annual from hell and I managed to get a good price for it. So I started looking at things with engines that go round and round instead of up and down and the CL just didn't seem to get the blood up like I thought it should for the bucks and I had another use for the bucks. After 911 the whole genav scene is somewhat muddled so who knows, maybe back for another look at the CL although I still doubt I will get one, not old enough yet. Going to look at the new seven but that is likely to be an exercise in futility because I have already decided from the pictures that I don't like the looks and I really question this Germanic bent toward electro-tech (how about that for being pre-judgemental). May have to come with an LCD so you can pull up help screens while you are driving in case you forgot how to open the glove box. Really have to have time to enjoy looking for these things and my free time is quickly coming to an end due to work (spent the morning with the AF and that program will be under contract by probably Feb at the latest). Doesn't make too much difference, with a lot of these toys, wanting them is better than owning them. You want to park your CL55 at Wal Mart while you run in for that case of Mobil 1? Then again, maybe you do..... Still can't believe that as an honorary Mean Gene Old Fart I was out in a driving rain storm trying to beat the VSC.

GS4Will

hey Ron,

did not mean to put you on the spot just that sometimes i day dream about things like that... and yes, when time comes, one day i would stop by wal-mart for couple jugs of M1 with my cl/s55 , or carrera4 wide body..... man you know me well