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Downshift on icy road?

I own a 2013 Ford Fusion with automatic transmission, All wheel drive, traction control, and of course ABS. I live on top of a hill in Fairbanks, Alaska so have to deal with a steep icy road 6 months of the year, such that I either have to downshift or brake to keep from going too fast. Years ago, I learned on a 2WD manual car, and so learned of course the importance of keeping the front wheels turning at all costs by limiting braking and downshifting before beginning the descent in that type of vehicle. I know NOT to downshift in a front wheel drive only car for similar reasons. However, with all the computerized functions of a modern car and all wheel drive, I just can't wrap my head around whether downshifting prior to starting down helps or harms my control over leaving it in drive and using brakes with ABS for backup, with the goal being to have as much drag as possible on the rear wheels to minimize the chance of front wheel lockup. Does traction control do anything if the engine is exerting drag and not propulsion to the wheels? Is drag evenly distributed to all 4 wheels in all wheel drive, or in the 75%/25% rear to front ratio that propulsion is distributed? I should mention that I have differing opinions from Ford's help line, the automotive instructors at the local technical college, and a large driving school. I'm hoping someplace out there is a real engineer who can offer facts based on actual test data.
And yes, I know to go slowly, have good winter tires, etc. etc.
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Comments

  • I have 50+years of proffesiona driving, all of it running out of Buffalo NY, at lot of it running to places like Watertown NY.
    Abs is specificly designed to keep your wheels turning, If you need to stop in a hurry, brakes only will provide the most stopping power but using the transmission on the hills will stop the brakes from overheating on long grades.
  • Thanks, Oldtimer, but I worry that downshifting will put drag on all 4 wheels and could defeat ABS if the engine drag itself causes wheel lockup. That's what I don't know in a car with all these features.
  • To me, the center of your question is:

    Does traction control do anything if the engine is exerting drag and not propulsion to the wheels? Is drag evenly distributed to all 4 wheels in all wheel drive, or in the 75%/25% rear to front ratio that propulsion is distributed?

    Until Ford lets you ask someone in the engineering department you'll never get a straight answer, but as far as I know ABS can only alter things by modifying the pressure in the brake lines, when the brakes are applied, so that wouldn't play a role in engine generated drag. Traction control slows a spinning wheel, but your problem is from sliding or locking wheels, not spinning wheels. On the other hand, I drove a Fusion recently and noticed that when in cruise control the transmission downshifted itself to slow the car on long downhill road sections, so it was responding to the speed increasing beyond the preset. Clearly, you would not be using cruise on an icy hill, but it could upset things for you if it downshifted on its own in a delicate moment when you are controlling slide.

    Like most of what I learned over years of driving on icy roads, an long empty downhill area, no other traffic and open fields on either side of the road was the best place to mess around with different ways to control the car. At least that way, if you completely mess things up and end up off the road, there's no real harm done.
  • Wentwest, you have hit it spot on. The trouble with the experimenting is that the conditions have to be exactly the same every time to do a valid comparison, and you have to do the experiment over and over to account for tiny differences in speed, brake pressure, etc. That's what makes it so tough. At least if I could get to someone who really knew how the system was designed I could start with a more educated guess.
  • edited January 11
    @Cosna....I used to live on a mountaintop just out of Fairbanks on the Chena Hotsprings road. I just drove slow and downshifted (one gear only) before I went down the incline. My wife and I had no problems driving in the area. Slow is the key. The fact that you have AWD and traction control should make this a piece of cake for you. Remember....driving slow when it's icy is the best thing you can do. I don't think an engineering explanation will do you any good because you have to deal with snow, ice, melting snow and ice, curves, gravel and any number of other road conditions. You have a great vehicle there so most of your concern is overthinking in my opinion.
  • I think a moderate amount of engine drag is the way to go. Just enough to keep road speed from increasing rapidly.
    Downshifting but not over say, 2000rpm.
    Traction control may help by applying brakes to individual wheels while the driver has no foot on gas or brakes, IDKFS.
    While ABS has the advantage of controlling individual wheels its application is rather abrupt, which isn't ideal in ice and snow.

  • edited January 11
    Thanks, Missileman. I've lived in the same house on Chena Ridge for 40 years, and so far have managed fine. However, every once in a while I have had an unpleasant surprise that got my pulse going. The more I have learned about cars, the more obvious it is that a lot of engineering and thought goes on behind the vehicle that otherwise looks so straightforward, and I want to take advantage of that. My daughter is starting to drive now, and I want to give her every edge I can, and that means to me knowing the system inside and out. It only takes once.

    And, circuitsmith, that "feels" right to me also; put on some baseline uniform drag then add braking. I just wish I knew more details on what traction control has to offer, and if it is uniform or differential.
  • edited January 11
    The slipprier it is, the less you can use engine braking. If you have ice on the road and no sand or salt, the closer you get to 32 degrees the less traction you have. I have had glare ice conditions with a tractor trailer where I had to shift into neutral to avoid locking my drive wheel and taking me off the road. Obviously, you can't do that on a curvy downhill.
    At 25 below ice has pretty good traction
    We didn't have ABS on tractor trailers, there was a Federal mandate to require it in the late 70s when the Feds required the states to raise the weight limits on the interstates from 72000 lb to 80000 lb but it was such a disaster that it was soon discontinued. You have not known real excitement until you have taken a loaded tractor trailer through a toll booth at 60 mph because it wouldn't even slow up while tha ABS was going psst,psst,psst.
    Bank alarms, and many other electronic devices used to make them act up.
  • Oldtimer, you are totally correct. When it is really cold, there is little issue except when it is really REALLY cold, like -50, both ABS and power boost can unexpectedly quit, and that makes for excitement as well. We rarely get freezing rain, but the last few years we have had one or two episodes, and then it is a whole new world, and that is where I want every edge going for me (and my daughter) that I can learn, which is why I have this post. Even after 50 years on the road there are new ways to get hurt that I discover regularly and it causes me to be more cautious, not less. Clearly, you feel the same way. It really worries me to be sharing the road with someone whom I overhear remark that they are a really great driver and think driving is easy. I am most grateful I only have to handle a passenger sedan and light pickup. You big rig drivers have my utmost respect.
  • edited January 11
    Today we woke up to an iced luge run for a road. The sander couldn't get in and I needed to take a friend to the air port. Two things about going down a glare ice hill. First DONOT rely on engine braking. The abs is designed to keep your wheels turning enough to steer and you only have steerage when the wheels are rolling on ice, not when they are locked when you have engine braking greater then the free wheeling Traction limit. Secondly, you can't generalize about ice ! Ice traction varies with temperature of the road and the atmospheric conditions. This morning where we live we had the slipperiest conditions as we had sub zero nights for several days making the dirt road vary cold with a 32 degree rain. The rain froze on contact but the watery mixture on the ice kept the ice at near freezing which is where ice is slipperiest.

    Any one who ice states or plays hockey knows cold ice has more traction and is slower then near freezing ice. When wheels lock, like an ice skate, the sliding friction tends to raise the temp of the ice making it more watery and giving it less traction then the ice under a tire that rolls. Engine braking in some cold ice conditions may work when ice has it's best traction. That's why you get varied opinions. But, when encountering ice in general, free wheel and use the brakes as instead to limit the wheel lock. With abs, you get more help.

    I came to these conclusions along with all the other ice racers who raced SAAB two strokes which cornered so well on ice, not because it was front drive, but it had a free wheel devise. When you released the accelerator it allowed all the wheels to free wheel. On ice it gaves us the best steerage. Racing on ice gives you a learning curve second to none. If you don't have steerage while going down an icy hill, you can spin like a top and loose total control. Not only that but you can slide faster then braking with abs with the wheels turning as the locked wheel creates a wetter ice.
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