Thinking about disconnecting traction control

Yes

On my 2008 Prius with good winter tires (which are a must have, of course, don't need to be a rocket scientist to know that), when the car is "stuck", I can floor the gas pedal. After a few seconds, the tires spin up to ten km/h, and go back down (if they're spinning). it'll keep repeating that over and over if I keep the gas pedal floored.
I can see the speedometer go from zero to 10 kph and back down. I also hear the drrzzttt-drzzztt sound of the tires spinning.
The car will plow through eventually. I'd say its "plowing" performance is slightly below average compared to compact-midsize FWD sedans, but it's not awful. Must be an improved TRAC logic, which hopefully older models cold get by a flash upgrade at the dealer if their TRAC doesn't do the above.

An even better improvement would be to allow the wheels to spin constantly at say 5 or 10 km/h.

The only time I got stuck was due to ground clearance, not TRAC.

 

Well I generally agree that the traction control can be a real problem in traffic. It isn't just when the tire slips because of lack of traction, it also engages when you hit a pot hole or even a big bump in the road. I remember changing lanes one time on a freeway onramp in a curve. I floored it to get into a faster lane, there was a car coming up from behind, and my while I was in mid lane change my car hit a bump and all power was lost, and the car behind me had to hit the brakes to avoid hitting me. If I were in a car without traction control, it would have been fine, but that scared the heck out of me.

My wife drives the Prius to work. I'm buying an 09 Subaru Forester in a few weeks to replace my 1991 Corolla. The Forester has a button to disable traction control if needed. Toyota should have put one in the Prius as well.

For any gravel roads, hitting a bump in fast moving traffic, the Prius is a very poor performing car. Outside of those places, I love it. Driving at 75-80mph from Portland to Seattle recently, we got 48.5mpg. Try that in any other car!

 

Hitting a bump or pothole causes a loss of traction, which activates traction control. It is a secondary effect. If you don't lose traction, the bump won't cause traction control to activate. The crappy OEM tires are the biggest offender in this area.

The traction control on the Prius is there to protect the HSD. Disabling traction control would condemn the drive system to almost certain death. That's why there is no disable button.

Traction control is one of the weak links in the Prius design. It was improved markedly for post 2005 models, but it still could be a lot better. That said, bad tires are the main problem. Are you running the OEM Goodyear Integrity tires? They are very poor tires, especially in the area of traction.

Tom

 

I mounted four 195/60R-15 GENERAL ALTIMAX ARCTIC (no studs) snows from Tirerack.com. No local dealer could beat their price of $277.90 w/ UPS shipping. I am sure that the more expensive Nokians or Blizzaks are great tires, but I can't afford them right now.

I live on the MA/NH border and it seems to be snowing every three days lately! I have about 5000 miles on them now and am very impressed with them. About the only thing stopping me is the ground clearance. I think it is pretty funny when the light turns green and I motor on through the intersection and watch the people on either side of me spinning and fishtailing. Watching in my rear view mirror of course! I have played around with them in empty parking lots and find they give you nice straight controlled "panic" stops. I have tried to get the traction control to leave me without power as I have heard some complain about but haven't been able to get it to react that way yet. I think part of the problem is sometimes driver behavior as well. I like the saying "drive like there is an egg between your foot and the pedals".

I just bought the Pri so my OEM tires are pretty new but I was very concerned about leaving them on in the snow as they would throw the traction control into a fit when accelerating on wet pavement, I can't imagine what they would have done in the snow!

The larger than OEM size also helps improve handling. I no longer get blown into the next lane when there is a cross wind. They are not that noisy nor does the ride seem to be that much rougher.

Gas mileage takes a hit, but it is cold out so it is going to take a hit anyway. Plus, I have still doubled my mileage compared to my Subaru OB wagon. With my limited experience thus far, I would say that the Pri with four snows handles about as good as the OB wagon did with all season GY Triple Treads. Of course, deep snow would be the limiting factor, but that has nothing to do with the quality of the tires.

This is the first FWD car I have put snows on and I would never drive a FWD car again without snows in the winter. And you definitely have to do all four.

 

Another data point: with my 2006 Prius, I have been able to spin the drive wheels fast enough to actually throw snow.

Tom

 

When the car pulse-spins the wheels?

 

Exactly. I had a very small amount of headway, so it let me spin them faster than you can do at a standstill. It surprised me to see the snow go flying and hear it splat into the wheel wells.

I got stuck in the end of our driveway today. We were away for a couple of days, and the temperature came up just above freezing, so we had big ridges of frozen packed snow and ice, covered with slippery greasy stuff. I didn't want to go fast for fear of bottoming out, so I just crept into it. After about two feet the Prius stopped dead. If I hadn't known better, I would have sworn that the front wheels had stopped, as people often claim with traction control, but I new they were spinning slowly. I did my usual trick of whipping the transmission lever back and forth from D to R, and rocked out backward. After that I used a touch more speed and powered through the slop and into the driveway. I think part of the problem with the Prius is that you can't hear the wheels turning. It's so quiet.

Tom


Tom

 

Me too, got stuck once.
The wheels spinning are hard to hear unless you lower the window, but I could see the speedometer go from 0 to 10kph and back down.

The wheels were spinning but the car wasn't moving (they polished the packed snow and made a nice ice patch), so a car without TC would have been as stuck.
Like Tom, I did the old D-R-D trick which worked like a charm.

 

Agree fully. It's not just about the tires. Have had the same problem.

 

I know this is an old thread, but with winter coming on again I am faced with this defect and wondering if Toyota has addressed it yet. We have a 2006 Prius. I have cursed the traction control system many times and consider it really dangerous. I never trust the vehicle to accelerate quickly from a full stop. There have been several times when I have had to do this to enter a fast highway with dense traffic and the damn thing hesitates right at a very critical moment.

When I read about this issue, I upgraded my tires to ComfortTreads. They did not help very much at all. Now I have to avoid certain hwy entrances completely. Then two winters ago we had weeks of heavy snow. Our uphill driveway was clear enough that our Honda Odyssey could make it up with a little wheel slipping as long as one had momentum. But with the Prius, which is a pretty good snow car, it was impossible, only because of the TCS. I have driven many cars and have a lot of winter driving experience. As designed, the Prius TSC makes a good car awful, just when you need it to let you be in control. To say this is the tires is BS.

We are now considering replacing the car because of this safety defect. We tried a Nissan Leaf, which has a TSC defeat switch. Has Toyota remedied the TSC problems or will it have a defeat switch on future models? Hope so, safety is more important than saving a few mpg.

 

I had some low resistance tires put on a month ago on my 2008 Prius touring - they are made by Firestone but I can't remember the name. Technically they are a summer tire - they do make an "all season" ULR tire but the Firestone guy said he recommended actual snow tires for winter (course he would ) Anyway, Oregon roads are usually wet wet wet, even in winter, and so-called summer tires have very good wet weather performance.

First experience in the snow last week, as I drive up into the hills for work, elevation 1600 feet: tires were fantastic! Last hill goes up about 400 feet, fairly steep grade, and I decided to see what would happen if I floored it. The surface was packed snow. Traction control flickered but I didn't feel anything - car actually surged forward. I was surprised at how hard it was to actually get the TC light to flicker. I sold my 2007 Honda Accord Coupe a couple years ago to buy my Prius so I have something to compare to. The Accord had much wider (also summer) tires and it had traction control. The TC sucked. The power would just be cut i.e., the power to the wheels was completely killed. The disable switch made little difference - the tires spun very fast but the car still didn't move. I was really disappointed in the performance of the Accord in winter driving (of course the 225hp with 6spd manual I do miss ....)

A little off-topic but I installed a stiffening plate which has improved handling with one exception - if my tires get into a rut of snow or a groove in the pavement - the car kinds of jumps likes it's being pulled onto a rail - very disconcerting.

 

what most people here probably don't realize is that different prii have radically different traction control parameters.
the first prius i drove was a 2005 basic model. it was owned by my girlfriend, and i put over 20,000 miles on that vehicle over the course of 2 years. i never had a single instance where the traction control seemed overbearing... summer or winter.

i recently bought a 2008 loaded prius, and the very first day i owned it the traction control almost killed me as i lost all power while turning onto a road with traffic coming at me at 50 MPH.
looking this up on the web, i figured that maybe the brand new tires that the previous owners had purchased before returning it from lease were causing my problems

yesterday i installed the winterforce snow tires from my previous car (VW Golf)... no difference.
i have a 150 foot driveway at work with a slight incline to it. the prius got stuck over and over again trying to climb with only 4 inches of fresh snow on it.
my girlfriends prius with factory tires has climbed this driveway with 6" of snow on several occasions with no problems. My VW would climb this driveway with 8" of snow and these very same tireson with ease.

 

Interesting post. The early Gen II Prius, like your girlfriend's, were known to have the most sensitive TC. In 2006 the TC system was improved and used on all of the remaining Gen II Prius, such as your 2008. Because of this, I would have expected your 2008 to do better than the 2005.

However, we also know there are significant differences from car to car. I don't know why, but some Prius seem unusually sensitive. This has been reported by PC members that I generally trust.

The mystery continues.

Tom

 

I've been trying to understand why disabling the TC could result in a transaxle failure. So far the only convincing argument I've heard is that if the car was allowed to rev high during a slip event, then suddenly caught traction, the chain in the transaxle could fail.

For those that don't know, there is a chain which couples the output of MG2 and the PSD to the differential. Supposedly if you were spinning the wheels, MG2 would of course be at high RPM. It's rotor has significant mass, along with the other components in the PSD, so supposedly a sudden grip when you find a dry spot could result in high dynamic loading of this chain and thus failure.

It makes sense, but since I don't have the numbers on these components, there is no way to do calculations to determine what kind of stresses they are talking about. I'd also have to know the capability and/or maximum loading capability of the chain without failure.

 

Until this year, I was squarely in the "traction control in the Prius works well" camp also. I've been through 2 tough winters in my 08, so I have plenty of experience.

This year I moved to a state with real hills.

A couple of days ago (1st snow of the year), I couldn't make it up my (hilly) development with only about 2-3 inches of snow on the ground! I tried every trick - just touching the gas - pushing it all the way down - turning the wheel both ways, etc. The bottom line is that I spent 30 minutes using every trick in the book with absolutely no luck. My tires are almost new all-season Michelins.

Some may think that it was just too slippery to pass. That was clearly not the case as I watched a FWD Camry just walk up and down the development at will. I asked him if he had AWD, and he said no - just FWD. His tires were certainly no better than mine and actually looked worn down!

The problem is with the Prius - no question.

There will be snow on this road for the bulk of the winter. I just don't see myself walking/falling up the 1/2 mile of road that lies between me and my house for the balance of the winter.

I absolutely LOVE, LOVE, LOVE my Prius! However, this has quickly become a deal breaker. If anyone has ANY thoughts (other than get snow tires: see Camry comment above), I'd love to hear them before I pull the trigger and trade for an auto that will make it to my house.

Thanks!

-Brad

 

Toyota's technical documentation specifically lists MG1 overspeed as the main risk in a low traction situation.

Tom

 

I've been to PA and those aren't real hills. I live on the front range of the Rocky Mountains, and go up a steep 2000ft vertical elevation change in the Prius multiple times a day as I live up there. The Prius (2006, so same TC as your 08) makes it just fine.

I am adament that it is all about the driver and the vehicle/tires contribute very little. I have made it up this incline in all vehicles I have and most are FWD. A thin layer of only ice is a good day on this road.

Your solution #1 of barely touching the gas wont help. Once you get going too slowly, your tires will just smush the snow, lose traction, and you will be flailing about. Faster is better, but you need to be able to control it.

Your solution #2 of mashing pedal wont work in the Prius because as soon as it slips, it will back of power, the tires will slow down, then your still mashed foot will cause them to spin right back up too fast and get no traction.

If the traction control kicks in, you're screwed. Turn down the hill and start again.

It seems like you also tried to do the zig-zag technique (turning the wheel left and right really fast). This is actually much harder than it looks. If you have not executed it before in tough conditions, the Prius is probably not the car to try it in since again if the TC kicks on you're screwed.

I am still making it up my 2000ft+ "hill" with 2 year old balding all season tires (Tiger Paw or something...). If you find yourself really stuck, then you can try to deflate the front tires most of the way, or just disable TC for the brief stint up the hill.

If it is still snowy where you are, I would find a good hill (that has a less steep route back up if you cant make it) and just keep practicing. After a while you may feel like a rally driver and will be able to feel that edge where the car is about to lose grip around a corner and be able to adjust for it without sliding back down.

 

I believe you, but I don't see how the HV ECU would allow this to happen unless it was shifted into neutral. Tom, Can you point me to where this is in the docs? (or show me the relevant doc)

 

It could only happen as a transient. Obviously the control unit wouldn't command an overspeed situation, but if one part of the PSD is spinning fast and suddenly stops, some other part of the PSD has to start spinning equally suddenly since the gears are permanently engaged. The converse, of course, is also true. This sudden change from fast to slow is exactly what can happen in a low traction situation.

Patrick had the technical documentation relating to traction control. If he reads this, perhaps he can post a link. Alternately, you can PM him.

Tom

 

hmm just gone done reading all of these posts from the beggining.. so many Negatives and very few that work.. from doing tires this way or that way.. Seems to me a flaw in general in most of the cars that come off the line?

I have one that goes all over the place.. just retarted.. i mean dangerous you turn a right over a patch of ice.. From a stop sign lets say, and bam the font of the car goes one way and the back end goes left into the other lane of traffic.. wow and keep in mine from a dead stop not flooring it, mabying going 1 mph.. and you go alll over? that is just stupid have at least 1 wheel have power vs just cutting it all together, where you just have to pump the brakes and gas it at the same time in hopes of the traction to come back.. I think its just as simple as .. the fact is its just to SENSATIVE..Right? yeah I think so or they just should make all cars 4 wheel drive or 2 wheel with a switch to engage.. there for you have 1 or 2 not gripping where the car then can use the power from the other 2 to get moving and eventually the other 2 wheels that are spinning get that traction that they nee.