Anti-Slip Technology

PJC your statement that all cars have four wheel braking is true, but not all the time. The Prius above 7 mph under normal braking condition "not an emergency stop or if the front wheels slide" is only two wheel braking, the fronts. This is because it uses regen to brake and does not use hydraulic assist. It is only below 7 mph that the hydraulics are used except in the conditions noted and if the HV battery is full.

John (Britprius)

 

I HAVE brand new snow tires on my 2007 Prius and I still need to disable the traction control occasionally...

I also live in Michigan.

The majority of members on this site have never experienced a midwestern winter, let alone a Michigan one. They are in sunny California, Texas, Florida, etc... and really have no idea what its like. I do, and I can personally attest that with winter tires (or tyres, whatever the hell makes you happy) there are many times we need wheel spin. NOT "damaging ICE at 7000RPM's redlining, rubber smoking, cvt transaxle smoking from the heat" wheelspin, but at least some wheelspin to rock the car out of snow!

Moving forward now (pun intended ), I use the same method to disable my traction control. I have the directions printed out and keep it in my glovebox, although now I have it memorized. I can also enter inspection mode with Techstream I believe.

 

Snow, Snow, Snow....

What about dirt, gravel, rocks, mud?

Don't get that much snow here, but when I do, I drive another car (usually an old Camry) and chain up the wheels because I do not trust the Prius in winter conditions in the mountain West.

But, there have been many instances where the Prius traction control (or lack of) has left me muttering in loose summertime gravel/dirt. Usually this happens when some sort of wild creature (deer, elk, quail, turkey, snake) dashes in front of the car and requires an emergency stop on a steep dirt pitch (actually, it does not even have to be steep).

So, I can relate to wanting to turn off the traction control....

 

I live in the Rocky Mountains and my Prius is the mountain goat that takes me skiing and up through the mountain passes all the time. It does backroad switchback passes with many inches of snow on it without a problem. Last night we had a 3-4 inches throughout the city and the Prius and I were zipping past stupid drivers going 15mph on the highway clogging the road when the Prius was fully capable of going full speed with full control.

I know how to disable traction control but have only ever needed to do it once. Otherwise if you are good with the pedal, you have no reason to spin the tires. I live on a mountain with a couple thousand foot elevation change up a non-plowed road between the main city and the house. The Prius goes up and down this hill everyday, usually multiple times a day. Never an issue. I also carry a set of chains in the car as required by law for some of the roads I travel on and have not yet needed them other then to make sure they are still functional once a year.

 

FWIW the traction control on the Gen III's is much less intrusive.

Still not easily defeated though.

 

Haha I do the same thing here in my Prius

99% of the time you are completely correct - I never have to spin the tires for any weather. But its that 1% of the time that gets ya. And I dont think there is much of an argument that gravel (some traction) is preferable to ice (very little/no traction). At least on gravel the tires get a "bite". On the ice, a little more difficult.

FWIW, today in my area its -8f with -35f windchill. Theres a lot of snow, ice, salt doesnt work on the roads when its this cold, etc etc.

 

Great. Just pulled up the National Weather Service Special Hazard Alert for my area:

SNOW AMOUNTS OF 6 TO 12 INCHES ARE
POSSIBLE FROM WEDNESDAY AFTERNOON THROUGH THURSDAY.
Not a chance my Prius will make it through that...

Where are those notes on disabling traction control...

 

Thats what Ive heard about the Gen3's. Maybe this week Ill go test drive one at my local Toyota dealer and see what all the hype is about

 

Im selling a 4wd SUV right now! You just have to drive cross country to get it..hehe

 

Anytime you disable the TC, you are doing so at your own risk....

BUT there are many members here that have disabled TC once, and done so several times with no ill effects.

As a matter of fact, I havent read one thread here, or at the other forums I frequent of anybody who has ever damaged/ruined or otherwise shortened the life of their hybrid drive from disabling TC. However, the risk of severe damage exists if you abuse (read: spin the wheels at high speeds and let them grab dry pavement, etc) the system while in inspection mode. Most of us that know enough to enter the Prius in inspection mode already know the risk and proceed carefully enough not to cause damage.

Its 4f out right now and Im sitting on the couch in my boxers. Tomorrow I will dig out the directions I have and verify they are the same but just looking at it and going off memory, it looks identical.

EDIT: Here is a youtube video on how to do it:

 

Sailracer- where in Michigan are you?

 

Ha Very cool. I have good friends in A2 and go there often.

Next time I come out that way, we'll meet up and do burnouts in inspection mode together! lol!!

 

Not at all. Also, I am from Canada, just across the border from you in Ontario in the Toronto area. I know heavy snow, I know ice storms, and here in the Rockies we get it. Denver is not in the mountains, it is a good 30 minutes to an hour from the front range. It gives pretty views because it sits far back, but it is not a mountain town. Where I live my house is literally on the front range mountain and the city is built up to it and then up it.

We get all types of snow. We do get the fluff that you can literally "sweep" off instead of shovel, but we also get the heavy wet snow where 1 shovel full feels like a pail of rocks.

Prius is fine in all these conditions. For your slush, don't touch the pedal. Let off the brake, let the car's "creep" to get you moving slightly, then apply pedal pressure slowly and more forcibly until up to the acceleration you want.

 

Do be very careful with the traction control disabled in slippery conditions. I think a primary concern is overspeeding MG2.

This is inference based, and my correct-to-way off ratio on this forum is very low, but for discussion purposes:

I gather that when a Pri is driving 41 mph with the ICE stopped, MG2 is spinning in reverse at or near "redline" speed. Then MG1 spins up the ICE and reverse speed on MG2 comes down.

With traction control off, and say one front tire is on ice, MG2 is capable of really zinging that slipping tire up to speed very quickly and effortlessly (high torque and low rotational inertia compared to a gasoline engine).

With the open differential between the front axleshafts, and research from my open differential-equipped Lego backhoe, when one axle/side gear of the open differential is stopped, the other side gear spins faster than the differential case...maybe even twice as fast.

So with one front tire spinning on ice and the other stopped on a higher-friction surface, MG2 may reach redline at, say, 21 mph. If it spins faster than this before MG1 gets the chance to spin up the ICE, MG2 may spin above its max rated speed in reverse...maybe greatly so.
***this is wrong...the ring gear would spin at half the speed of the spinning wheel***

I've somewhat trained myself to guess at the point at which traction control will activate. If I modulate pedal pressure to stay just below this point, I've found that it's possible to power the front tires slightly faster than the surface without traction control activating. This has been pretty effective for slush, combined with the electric crawl mentioned by 2k1toaster and the excellent snow traction of the all-season Hankook Optimo H727 (no, I don't work for them). This past Monday, I was re-affirmed of how confidence-inspiring a snow car a Pri can be, driving to and from a meeting (that ended up being cancelled due to the weather).

 

With one wheel spinning the ring gear speed in the differential would be half the speed of the one spinning wheel.

That being said, I agree with you overall. There's no better car than a Prius for modulating power to the wheels, particularly if you put it in ECO mode.

 

What tires do you have? I live in Fort Collins, but I do ski. I'm thinking of replacing my OEM with Nokian WRG3. Any thoughts? Yeah, I know they are expensive. I don't really care. I can drive in snow just fine, but I'd like better grip. Would rather not hassle with winter and summer tires. Plus I've been surprised at how well the car handles on the OEM tires in our flat-land, mild winters.