vehicle traction control danger on prius?

<div class='quotetop'>QUOTE(sea-horsea @ Aug 15 2007, 12:05 AM) [snapback]495975[/snapback]</div>

My very first question would be, "Have you ever driven a front-wheel drive car prior to the Prius?" It's not meant to be antagonistic--just that driving a front-wheel drive car in slick conditions is very different--including the notion that you steer into a skid.

 

<div class='quotetop'>QUOTE(yakiprius @ Nov 4 2007, 09:35 PM) [snapback]534762[/snapback]</div>

The hard little stock tires are the worst possible thing for loose sand. Don't expect them to do what they are not designed to do.

The antispin system does indeed mean that one will not get through snow using rocket action alone. On the other hand it is impossible to stall the Prius engine, therefore on a slippery surface one should always try going slower with a constant light touch on the gas pedal. 1 MPH and even 0 MPH on the speedometer are completely reasonable.

 

As I think those of us who have had TC problems can attest, the problem isn't the ability to drive in winter conditions, rather the lack of being able to. Once the car is moving it drives quite well. The issue is getting the car rolling from a dead stop, particularly on even a slight incline. Put yourself stopped at the end of an exit ramp with a inclined grade and attempting to pull into oncoming traffic when the car just doesn't move, or worse moves into the oncoming lane only to have the wheels stop turning. It's dangerous and has nothing to do with driver's ability.

Sure, if I ONLY drove in that "majority of conditions" all but a few times a year I would have had no problem keeping the OEMs, but for those of us who still drive regularly in winter conditions several times a year over the span of 4 months the Integrities are inadequate. Fact.

 

I had a "no motion" experience which I finally wrote up as part of
another page, on ice, but the front wheels *were* turning which is
why we were drifting toward the ditch instead of sitting still.
.
I still think the dozens of angry threads that pop up about this
every winter is largely pilot error, in varying degrees.
.
_H*

 

<div class='quotetop'>QUOTE(hobbit @ Nov 5 2007, 12:31 PM) [snapback]534967[/snapback]</div>

I disagree. How is the fact that the wheels don't turn driver error? I think the fact that there are dozens of people who experience a this problem only confirms that the issue is mechanical. How many people have to get the flu before it's an "epidemic"?

I'll grant you that there is a degree on "learning how to drive the PRIUS in the snow" that needs to be taken into account but the vast majority of people learn to drive traditional cars in the snow. I think for a first time Prius driver with stock tires the learning curve for driving in the snow can be, at the least VERY frustrating, if not dangerous.

I know there are many people who have not had negative experiences with TC and the snow but there isn't much you can say to convince me that the Prius is a "good" car for the snow. IMO it is without a doubt a weak point of the design. It's adequate but honestly I have felt more comfortable in my previous FWD cars (Corolla and Matrix) than the Prius. When it came time to replace our 2nd car we bought a used Subaru w/AWD for this very reason.

 

<div class='quotetop'>QUOTE(hobbit @ Nov 5 2007, 11:31 AM) [snapback]534967[/snapback]</div>

Pilot error???
Well lets see..I'm 50 years old, Have driven well over 2 million miles (semi truck included) Mostly in Minnesota and washington state. Over Snowy mountain passes.
And this particular PRIUS that won't go when you push on the accelerator, is somehow MY FAULT...
I don't know how they do it in the North East.. But I usually press down with my right foot either gently or not so gentle...either way the car goes into NO POWER mode ...
I'd be happy to try something different if anyone has some ideas...

<div class='quotetop'>QUOTE(yakiprius @ Nov 5 2007, 12:19 PM) [snapback]535002[/snapback]</div>

Also I run top of the line studless all season snow tires. So tires is NOT the issue here either.

 

<div class='quotetop'>QUOTE(yakiprius @ Nov 5 2007, 10:21 AM) [snapback]535002[/snapback]</div>

You don't get it. It's never the car's fault. It's always the drivers's fault. That is the mantra of the Prius apologist.

 

I've never had a problem with the traction control/VSC in slippery conditions. Meaning snow/ice wearing snow tires (in Yakima WA, in fact), and on wet roads wearing the stock tires (in Portland OR) and even on mild dirt roads (in Tahoe CA).

Overall, it seems the Prius was designed for average drivers doing ordinary daily driving in normal conditions on paved roads. Under those conditions, the electronics seems to work fine.

I can see that it's not great for sliding through turns, for clawing up loose gravel/dirt slopes, for laying rubber, for skittering on snow wearing summer tires. For those conditions, a traction control defeat button would be useful. I can sort of understand why the Toyota engineers didn't make that much of a priority.

P.S. to yakiprius, last winter we were in Yakima, had Blizzak snow tires (no studs) on the Prius, there was a decent amount of snow and ice on the ground. I wanted to see how the car would handle snow and ice, having read threads like this. I took it to the Raley's parking lot, which was basically a lumpy sheet of ice. Floored it, the car accelerated fine, no wheelspin and the car simply went forward. Went to a snow-covered side road near my in-law's, about 3" of snow, floored it, car accelerated fine. Took the kids to a movie, went to the end of the parking lot where no-one had driven, also about 3" of snow, drove in circles trying to get it to spin out, car didn't spin but it did accelerate okay. Drove over the hill to Tieton, watched a Blazer with mud/snows fishtail and nearly go off the icy road, we were motoring along peacefully. Drove home to Portland over the pass, road was hard-packed snow, car drove fine. So I don't think the traction control/VSC makes the Prius undriveable in the snow at all.

 

TC isn't at fault, guys. Yes, the TC in the Prius is overzealous. No, you're not going to do any better without it. I live in Colorado and we got nailed last year with double-blizzards (many of you probably know about this already). The Prius didn't do any better or worse than our 2002 Ford Taurus. It did significantly better than my friend's Nissan 300z (which is RWD).

The Prius is a front-wheel drive vehicle. The stock tires aren't particularly grippy. Don't expect miracles.

Do I wish the TC let me spin the wheels more? Yes. Do I understand why it doesn't (to protect the motors)? Yes.

But, the bottom line is that if you live in an area with such conditions, you should probably have an AWD or 4WD vehicle on hand. We got our Taurus stuck in the snow several times (along with the Prius) last year. Neither has the ground clearance or traction for that kind of weather.

Now, the Prius does fine on gravel or dirt, even on hills. One of my friends lives at the top of a hill with a poorly-maintained gravel hill. I'm able to get up there even when it's wet. I can trigger TC if I floor it, but if I'm not heavy on the accelerator it works fine.

Part of this is technique. If you're triggering TC, either you're pushing too hard or the surface doesn't have enough traction. It's counterintuitive for the car to kill the throttle, but this is how TC works. The Prius is on the heavy-end of the spectrum (as most Toyotas seem to be with TC/ESP), which provides better protection for your tires and the transmission. It also makes it easier to activate.

If your TC is activating on moderate traction surfaces (gravel, light snow) with light acceleration or on surfaces where you have plenty of traction (dry pavement), check the tires. They may be overinflated or worn.

Increasing your tire pressure will decrease the traction you get. Replacing the tires with something grippier will help, at the expense of some MPG.

 

<div class='quotetop'>QUOTE(jayman @ Nov 5 2007, 11:28 PM) [snapback]534892[/snapback]</div>

Would anyone really floor a car on ice? Doesn't seem all that smart to me. Wouldn't you go easy on ice like you would on wet clay? (something I am familiar with driving on) Tip toe not tromp. If you drove any front wheel drive car like troping it on ice would you really go any faster? Wheel spin isn't the fastest way to get moving, ask a drag racer!

I just asked my 14 year old son what would he do if he went to take off from a traffic light and the car didn't move forward because the traction control was detecting wheel spin, he said he would lift his foot off the accelerator and press it more gently. If my 14 year old who has never driven a car knows that how could anyone who has driven a car not know it?

 

<div class='quotetop'>QUOTE(patsparks @ Nov 6 2007, 05:32 AM) [snapback]535376[/snapback]</div>

I think the poster's point was that EVEN IF you stomp on the accelerator, nothing happens. The wheels don't turn, period. Obviously I cannot speak for jayman and how he typically drives but I think most of us with experience driving on icy roads would agree that most of the time you (and your smart 14 year old) are correct, that slow and steady on the pedal is the way to approach these conditions but that's our point. Sometimes regardless of HOW you use the accelerator the TC kicks in and the car refuses to move. Moreover, you should know that sometimes spinning the wheels hard can be an effective way to wiggle your way out of a tough spot.

 

<div class='quotetop'>QUOTE(patsparks @ Nov 6 2007, 03:32 AM) [snapback]535376[/snapback]</div>

Patsparks:

Jayman is absolutely correct. If you read his post carefully he says :

"The light turns green, you press the accelerator pedal, and ... nothing. "

...Then he also says that nothing will also happen even if you floor it !! Any other car will move. What do you think I am driving now?

I have 3 2007 Prius. Not one, not two... three of them! So I know what I am talking about. Sadly, I have them limited to city center duties only (as company vehicles) where the streets are likely to be cleaner and sanded more regularly. One of those cars was on my garage last winter as my wife's car, and we had our own tales even though the 2007 TC governing software is supposed to be markedly improved over the previous years.
By the way, all our 2007 Prius' have a winter tire change with Michelin X-Ice and they still act at times. Perhaps unless you have studded tires, as Jayman says, I believe the traction ability can still play a few tricks on some of us.

Cheers;

MSantos

 

well, bohus, since you're local, you wanna tentatively schedule a
"snow day" when we get our cars together in a parking lot and see
if there's any difference in behavior? I'm still curious about this,
regardless of the conclusions I've made about cause.
.
Now, riddle me this: how is the car "avoiding wheelspin" by simply
refusing to move the wheels? How does the car know what kind of
surface it's sitting on? It doesnt. All it can try to do is MOVE
THE WHEELS, and then make subsequent decisions based on what happens
with torque and speed.
.
Does anyone remember this chart and discussion?

It's going to take a whole lot of hard in-my-face evidence for me to
ever believe that anyone's car isn't at least TRYING, no matter how
delicately, to rotate the wheels. I do observe that it tries a bit
differently based on accelerator position, but never a complete
refusal to try at all because there's no way for the car to "know"
about the surface under it beforehand.
.
_H*

 

My experience is that the Prius will spin its front wheels in limited traction situations, but it won't race them as would happen without traction control. Hobbit is correct that the traction control must allow some spin in order to deduce that there is a traction problem. Otherwise, any time you stopped, even on dry pavement, you would never be able to start again because the back wheels were not turning.

The issue, then, becomes one of how much wheel spin is allowed, and how much accelerator pedal pressure it takes to get it. The Prius never allows much wheel spin. The wheel spin is done with so little fuss that I suspect many drivers are unaware that they are getting some spin. The Prius traction control is also very protective: if you want it to try harder, you have to really push on the accelerator. Mash it all of the way to the floor if you are serious about spinning your way up a hill. This is counter-intuitive for most drivers, much as not pumping the brakes is counter-intuitive for anti-lock brakes. You have to get used to it. With the Prius controls, you are telling the computer what you want the car to do, not how to do it. If you want it to go faster, push harder on the accelerator; if you want it to slow down faster, push harder on the brake. It's almost too easy.

I see two major factors with the Prius relating to limited traction situations: 1) The OEM tires are not good all-season tires or winter tires, and also have trouble in sand and gravel; 2) While the traction control allows for some wheel spin, it tends to produce slow power pulses. For example, when driving up a steep gravel road the front wheels began to slip; the traction control kicks in and cuts power which allows the tires to grab again; the wheels turn and slip again, and the cycle repeats. You get a sort of "Rmph, rumph, rrmph..." sound as the power comes up, the wheels spin, and power is cut. There are a limited number of circumstances where an experienced driver can use wheel spin to an advantage. This "Rmph, rumph, rrmph" cycling prevents that from happening. I would prefer having wheel speed limited but not cycled in low traction situations, but it may not be practical with the HSD.

I will leave you with two other thoughts: 1) The Prius is a car, not a truck, and has limited ground clearance. Don't expect it to wade through deep snow; 2) If it's really slippery, your car isn't going to move, with or without traction control. With the Prius, you may not know how slippery it really is, and so tend to blame the traction control when the car won't go.

Tom

 

<div class='quotetop'>QUOTE(patsparks @ Nov 6 2007, 04:32 AM) [snapback]535376[/snapback]</div>

I appreciate what you are trying to say.

I was taught to drive in real winter conditions, which means you pretend there is an egg between your foot and the accelerator pedal. For 25 years that has served me well, the only time I've been stuck was when I had to "exit" into a ditch to avoid a jack-knifing semitruck. That was almost 18 years ago, and I still have fond memories of my near-death experience

On glare ice at -25 C and colder, very gentle pedal pressure at a green light will result in very mild wheelspin if you are running "all season" tires. If you are running studless winter tires (Very soft tread compound, some have special gritty materials added to compound) or especially studded winter tires, that pedal technique means you just move. Period.

However, when the car conks out in the middle of an icy intersection, and traffic is bearing down on you, it's sort of instinctive to floor it. On the glare ice, it didn't matter if I used very gentle pedal pressure or put the pedal to the floorboards, the wheels barely turned. That was running Michelin Harmony "all season" tires, my dedicated winter tires had been backordered

The best experience was when I tried to go up the parking ramp at Polo Park mall, and the car simply stopped halfway up the ramp. A very old used up s***box rear wheel drive Dodge had no problem making it up the ramp, but that old car had studded tires.

I've had experience with Dunlop Graspic DS-2 and Yokohama Ice Guard 10 studless winter tires on the Prius. Both studless winter tires dramatically improved snow traction, and improved ice traction. However, glare ice was still a challenge. Better than the "all season" tires, but still the Prius had a hard time launching, while cars beside me were able to move with minor wheelspin

Once I got the studded Goodyear Nordic tires from Canadian Tire - the same tire is the Goodyear Ultra Grip 500 in Europe - I transformed the Prius into a good winter car. The tire is noisy on dry pavement, but I feel the snow and especially ice traction is very much worth it

However, once the car bogs down, I cannot "rock" it out. We had some pretty serious blizzards last winter, and the New Years Day one I was stranded at my hobby farm. I drove over to a neighbor about 6 km away to wish a Happy New Year, and managed to bog down in a drift right at the highway. No rocking, no nothing. I called the neighbor for help.

He came over in his wife's Ford Focus station wagon. One thing he did in falltime was put on the studded Goodyear Nordic tires, as I had been singing their praises. He had NO TROUBLE driving around my stuck Prius, though he did have to rock his car once to get it moving

He's a long haul truck driver, and has reported similar issues on newer highway tractors with electronic traction control. He suggested rapidly flooring and releasing the gas pedal, that seems to work on the highway tractors when he doesn't have enough time to poke the trac defeat button

I've tried the rapid pedal dance on the Prius and it does seem to work. You are right in that keeping a gas pedal floored - or rapidly pumping - on ice with a conventional car would be very dangerous.

My 2007 Toyota FJ Cruiser also has full time electronic traction control. However, that system works by applying the rear brake to the spinning tire, and it works very well. I only wish Toyota had thought of implementing the brakes for their traction control on the Prius. The braking is already electronic, it would have been easy to implement.

 

<div class='quotetop'>QUOTE(jayman @ Nov 6 2007, 12:35 PM) [snapback]535533[/snapback]</div>

Some Prius drivers have reported good luck with applying both the brake and accelerator at the same time, somewhat simulating the FJ traction control that you describe. I haven't had the opportunity to try that yet, but I'll give it a test once the conditions are conducive.

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Nov 6 2007, 02:33 PM) [snapback]535644[/snapback]</div>

Sort of like powerbraking? I haven't tried that, will give it a shot. Thanks

 

<div class='quotetop'>QUOTE(hobbit @ Nov 6 2007, 10:51 AM) [snapback]535474[/snapback]</div>

I'm not sure if you are just trying to be snarky but either way I think this would be a terrific idea*! I would love to approach this in true Mythbusters fashion with different tires and pre-post upgraded TC software. One problem off the bat is that we have identical cars, right down to the color (diff pkg though). It would be great to have a '06-'07 model with the less aggressive TC and some controlled conditions. However, I also recognize that just by me showing up you would have already partially proved your point

Look, you can post all the tech info, graphs, pie charts and handwritten notes from the engineers who designed and built the TC system and it won't change the fact that I was almost stranded in Owl's Head Maine with my infant son in the back because I couldn't get up a small hill regardless of how I manipulated the accelerator. This was 2 years ago and I immediately upgraded my tires and seeing as we barely had a winter last year the jury is still out on how much they will improve my ability to get the tires rolling in similar conditions.


* this would actually be the second time we meet. I spoke with you briefly at the Alt-Wheels festival last year in Brookline


edit: OK, I know I said we have "identical cars" but I now recall that Hobbit's car is truly one of a kind. So before I am corrected, I stand corrected )

 

<div class='quotetop'>QUOTE(sea-horsea @ Aug 15 2007, 01:05 AM) [snapback]495975[/snapback]</div>

I have had a half dozen instances of the too aggressive traction control stopping my '05 Prius. At least four instances of coming out of a paved parking lot to a heavily traveled paved road and having a little (not easily seen) leftover grit that had been applied to the winter snows stop my Prius DEAD for a second or so. I know not to floor it but there are times that you have to be aggressive or wait for a long time. These occurred with the OEM tires and with Michilin Arctic X tires. This is the most dangerous situation and I feel that Toyota has to address it before someone is seriously hurt. I have also had two instances of trying to drive up very steep grades. One was a snow covered paved driveway. The traction control slowed then stopped me less than 6 feet from the top. I had to back down a narrow lane to go out the lower alternative route. I know snow and winter driving (50 years in PA and Alaska driving) and know that the Michilin tires could have cut through the thin snow layer and made it the last 6 feet. The last incident occurred yesterday on a steep loose gravel driveway. No rain no snow - a cloudy but dry day. The traction control slowed my to a dead stop halfway up the steepest part of the driveway. I managed to creep the last hundred or so feet at 2 or 3 mph.

Is it possible to reprogram the traction control to lessen the aggressiveness? I posted an email to Toyota after several of the driveway moments and the snow covered hill. They said "Please note that traction control cannot create traction where there is none. Toyota recommends exercising extreme caution when pulling into oncoming traffic on any surface with poor traction." The problem is that there is always "some" traction and the traction control has defined "no traction" way too high for people that have to drive in the borderline conditions. This is not a hybrid problem this is a "definition of no traction" problem that the controls on the Prius are using.

 

Time to post this link again:

http://www.youtube.com/watch?v=1tSy5tHtT1g


This is how a car with proper traction control operates. I did not see any spinning tires when the car went up with the traction control enabled. When the front tires went from ice back on to pavement I didn't see the wheels slow down.