Unbelievably poor performance on snow

Discussion in 'Gen 2 Prius Main Forum' started by Dolgon, Dec 3, 2008.

  1. patsparks

    patsparks An Aussie perspective

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    I agree Tom, don't use B mode, just brake a little harder if you need to. This allows the ABS to work just the way it should and allows more regeneration during braking.
     
  2. van-island

    van-island New Member

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    Had a light snow here in Vancouver the other day, and my 2009 Prius performed well. No traction problems, and good braking on moderately icy roads. Using the OEM Goodyears, although I can't say the conditions were THAT snowy.
     
  3. hyo silver

    hyo silver Awaaaaay

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    That was a pretty light skiff of snow, compared to say Nanaimo that got two feet. Anyone who lives in a place that gets an actual winter would only laugh. Still, thin ice isn't any easier to drive on than thick ice, which is what the snow quickly turns to here. More on the way! :)

    Isn't it nice how easily the Prius always starts up in the cold?
     
  4. Romeo

    Romeo New Member

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    Well, as you pointed, most people use 2 or 1 during acceleration, not when breaking. Canadian driver manual recommends declutching to N when breaking on icy roads, that means pushing the clutch forward (from D to N, not backwards from D to 2). Mostly for that reason I have never tried shifting from D to 2 in emergency breaking. In most cases you need emergency breaking when stopping on red lights or at the intersection, so most likely the car is already in 2 or 1 gear, switching to 2 or 1 would have little effect. Switching to N would always have effect, and switching to B in Prius has even better effect IMHO.

    Those who are skeptical about effectiveness of B-breaking, please try it first, then criticize. I wouldn't mention it if I didn't feel the difference from just using the breaks. I find it effective because it feels like something is pushing the car backward from the outside and also ABS is almost never engaged (as we all know ABS is increasing the stopping distance, not decreasing). My biggest concern about B-mode though is whether the stop ligths go on when the B-mode activated. If not, then using it might be very dangerous if there is a car behind you.
     
  5. xsmatt81

    xsmatt81 non-AARP Member

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    we got our first snow this year in Vegas on the west side of town..about a foot. Mostly slush

    decided to take a drive up to Mt. Charleston to see how much had fallen out that way in the prius. At about 6700 foot elevation it was getting heavy, a good 10-17 inches of snow(4 on the road) after plow. I made it quite a ways up the hwy before the lodge, but had to stop short about 4 miles, the poor prius and stock tires could not budge on the ever gaining incline.

    to note a newer model nissan maxima just behind me, that I waved to go ahead had no better luck another 200 feet up the road LOL..they got stuck also.

    Need chains at least..but really in the conditions I was in..4x4 and all season tires would be best.

    it was fun, on the way down me and my girl made little snow men on the side of the road and went home.
     
  6. xsmatt81

    xsmatt81 non-AARP Member

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    used B on the way down, and it works.

    or just gentle push on brake was fine also in the snow. It was just above freezing on the OAT according to the car reading, so ice on the road was a possibility, but faint.

    B really slows this car down, and even in D I have never seen a car slow so quickly from the trans.
     
  7. qbee42

    qbee42 My other car is a boat

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    Been there, done that. I have tested it and it's not more effective. It *feels* effective, but it's just an illusion. It will not shorten the stopping distance in slippery conditions (or any others, for that matter), and it will not improve the control of the car.

    As for the brake lights, no, they do not light when you shift into B mode. The do still work when you press on the brake pedal, obviously, even in B mode.

    Tom
     
  8. nooaah

    nooaah New Member

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    First drive in the snow last night. About a quarter inch of snow on the roads in certain areas. Didn't have any trouble going up steep hills or stopping. I ended up taking the really steep hills when the ice started coming down and still no issues.

    I think I'll be getting the Tripletreds as my all season tires, though considering all the business travel I'll be doing up in New York and Central PA (mountains).
     
  9. Bonniesc

    Bonniesc New Member

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    I have a 2007 Touring edition Prius.
    In general I love the car.
    It is an absolute death trap if there is any snowflake within miles!

    I am am an extremely careful driver; a real estate broker who has people in my car continually. I am terrified of putting passengers in my car in cold weather.

     
  10. effwitt

    effwitt Paparazzi Magnet

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    Is West Bloomfield hilly? The only time I've had a problem was the original posters driveway and once on an unplowed, steep hill just to see if the Prius could get going from a standing start.

    Oh and welcome to PriusChat! :welcome:
     
  11. ewhanley

    ewhanley New Member

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    What is all this about the Prius being so horrible in the snow? It is the only vehicle we own, and we live in Alaska. Seriously, put on a decent set of winter-specific tires (studded in our case) and the Prius is a tank.
     
  12. Presto

    Presto Has his homepage set to PC

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    Get winter tires. It's as simple as that. It's my first time, ever, on winter rubber, and I love it. I know the feeling of driving the Prius without proper rubber in the winter. There's the mantra of, "Am I gonna make it?". I had trouble getting out of the garage because of the slippery ramps, and knew that was a precursor to traction troubles. Winter tires will give you confidence in driving in the snow/ice. The ramp is beyond trivial, now. I drive up and down that slippery plane with no worries.

    I wouldn't mind a little less grip in the rear, but that's just me. :)
     
  13. Romeo

    Romeo New Member

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    Well, I guess my post caused some confusion there. I only wanted to mention B-mode to drivers that might not realize that it could be used in addition to breaks. Neither engine breaking nor shifting to N will make the stopping distance shorter comparing to the breaks. But it is a very effective technique if applied together with breaks - it does shorten the distance and that is why it is officially recommended.

    With Prius, there is no 1 or 2 gear option and it is very difficult to shift to N during emergency breaking because you actually have to push and hold the shifter for a couple of seconds. You usually don't have these couple of seconds on an icy road with cars in front of you. That is why I was rather frustrated that the only option available was <<breaks>> which is less effective than <<breaks + 1,2,or N>>.

    When I discovered that B-mode could be used in addition to breaks, I was very happy and wanted to share my discovery with other Prius owners (especially with newbies like me). It might be not more effective than breaks but together they do a wonderful job. And I think that activating/deactivating B-mode is much faster than shifting gears, and that was probably why I said it is not available on other cars.

    So, the bottom line - do use B-mode in addition to breaks, it does make stopping more effective. You don't have to use it all the time, try it in different situations to understand when it is most effective and I am sure it will reduce your chances for an accident (don't forget that B-mode does not activate the red stop lights though, so watch for the cars behind you and use the breaks to inform them that you are slowing down).
     
  14. qbee42

    qbee42 My other car is a boat

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    But B mode does NOT make stopping more effective than brakes alone, even when used in addition to the brake pedal. The only good use of B mode for braking is descending long hills, where regeneration will max out the SOC. In that case B mode will forestall the use of pure friction braking. It is also useful if you want to scare the crap out of someone following too closely. B mode will make your Prius slow down without showing brake lights, but I don't consider that a good use.

    I will say it again just to make sure any casual readers are not confused: B mode will not shorten the stopping distance of a Prius, whether on dry pavement or slippery conditions.

    Tom
     
  15. Romeo

    Romeo New Member

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    Well, I disagree, but I think I need to add another clarification. The B-mode will reduce the stopping distance ONLY in cases when ABS is on. When ABS is suddenly activated, it's like you have no breaks. So, when you have no breaks, what other options to stop the car, especially with AUTO transmission? Shifting to lower gear or to N will stop your car faster than leaving it on D. Because on D, the engine will continue pulling your car until you run out of gas or press the breaks (but you don't have them, remember). The B-mode does exactly the same thing, it helps to slow down your car when you are loosing your breaks (e.g. when ABS is activated). So, any other conditions equal, the car that slows down from 30 miles on ice with working ABS will stop faster with N or B-mode than the car that will stay on D. It is a proven fact, you know.

    So, to correct my note, the B-mode will reduce the stopping distance in cases when ABS is activated. But hey, this is when you need to stop the most, otherwise, why pressing the breaks at all?

    So, if I know there is a chance of ABS to kick in, I'd better shift to B-mode just to help my car to stop faster if the breaks will suddenly become less efficient (if not inefficient) due to ABS.
     
  16. PriusDiver

    PriusDiver New Member

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    The big risk with this is that I don't think the traction control has anyway of detecting a "reverse slip" from engine braking producing a skid. This is a very real risk with using engine braking with reduced traction. ABS is effective because the wheel is either spinning or it isn't. Traction control is effective because either the wheel is spinning too fast or it isn't. I'm not sure the car has a way to correlate to the wheels under-spinning due to engine braking.

    Personally, on reduced traction situations I leave it to the ABS. ABS was designed for 1 thing and 1 thing only, controlled *braking* by counteracting the decrease of friction caused by a skid. Traction control was designed for one thing, to prevent wheel spin due to *acceleration*. Leave the ABS where it belongs, on reducing speed.

    As someone that has faced death due to a engine braking induced skid and loss of control, I would advise against using engine braking unless you are either at risk of overheating the brakes, or you are losing the regen braking due to a long downhill and reduced traction is not a risk.
     
  17. qbee42

    qbee42 My other car is a boat

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    Okay, this post has several serious errors. There is a lot of bad physics here, so let's look at this piece by piece and see if we can fix it:

    First a minor grammatical correction. It is brakes, not breaks, unless your brakes are broken.

    Now onto the technical side. Saying that ABS eliminates braking action is absolutely rubbish. You can't possibly mean this, so I am going to assume that I am simply misinterpreting your statement. ABS modulates the friction brakes to keep your wheels from locking up. A car with locked wheels takes considerably longer to stop, and steering becomes impossible. ABS allows the wheels to continue to turn so that braking action is improved and steering is possible. A really good performance driver may be able to manually modulate the brakes better than ABS, but not your average driver. With more modern ABS even this becomes doubtful.

    ABS will reduce your stopping distance as compared to locked wheels. Furthermore, the Prius will not allow B mode and ABS to be active at the same time. When ABS engages, B mode and regenerative braking are deactivated.

    First, you still have brakes as pointed out above. Second, your argument is not applicable to the Prius. The Prius uses "by wire" control for the brakes and accelerator. The engine never fights the brakes, regardless of what you do as a driver. As you press the brake pedal, the control system cuts power from the engine, then starts regenerative braking.

    B mode will toss away some energy by spinning the engine, but it will not increase the maximum available braking force. With plain regenerative braking or B mode, all of the braking is done through the front wheels only. Friction braking works with all four wheels, which is much more effective for maximum braking.

    Furthermore, B mode will not save you from ABS. Let's say you are trying to stop quickly on ice. You either press on the brake pedal, shift into B mode, or do both. Either way, the front wheels are retarded to slow the vehicle. You brake harder to slow down faster, and the front wheels start to slip. The Prius braking control ECU will notice this slip and immediately disable regenerative braking and B mode, and engage ABS friction braking. It does this because ABS friction braking is safer and more effective in low traction situations. You cannot stop this from happening, other than not braking so hard.

    This part is just plain wrong. The reasons are stated above.

    The good news is that you can use B mode if it makes you happy. The control system is smart enough to override your input if it becomes unsafe.

    Tom
     
  18. Romeo

    Romeo New Member

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    Well Tom, I can only accept your points as I don't have such deep knowledge of ABS and B-mode functions. I am glad I learned something today and thanks for correcting my spelling (always suspected there was something broken with those "breaks").

    It brings me back to the sad mood though because apparently B-mode does not work along with ABS. Which means that there is no equivalent of "ABS+N" mode on Prius. Well, technically it is available (you can always shift to N), but it is not as easy to shift as on other cars. I still think that "ABS+N" mode (shifting to Neutral when ABS is activated) substantially reduces the stopping distance comparing to "ABS+D" mode. Hope you at least agree with that also. I have always been switching to N when ABS kicks in on my previous cars and liked it, so not having this option on Prius is rather frustrating.
     
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Romeo,

    If you get into a driving situation where you need ABS, then you must be in a semi-emergency situation at minimum. I suggest hitting the brake pedal as hard as you can, continue steering to avoid whatever you need to avoid, and don't worry about shifting into N or any other gear. This is true no matter what car you are driving assuming it is equipped with ABS.
     
  20. patsparks

    patsparks An Aussie perspective

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    There is one exception to the "hit the brakes as hard as you can" emergency stop method. If by some slim chance all 4 wheels should lock simultaneously the ABS system will think you have stopped, in this case and only in this case, lift your foot and reapply the brakes instantly. This will allow all wheels to start turning again and allow the ABS to work again. If you don't get a 4 wheel lock up just maintain high pedal pressure and allow the ABS to do its thing.

    When you apply the brakes hard the HSD will go into neutral once you are going slow enough that regen finishes just like it does when stationary. Even if it doesn't the brakes are easily powerful enough to stop the car on a slippery surface and overcome any torque from the drive train. I doubt selecting neutral make any difference.
     
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