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Thread: Downshifting vs. Braking

  1. #16
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    In very slippery conditions downshifting can lead to skidding, yes, unless you're trying to do it it rarely happens though. In the slippery conditions it would happen I'd advice you to count on ABS though.

    This thread made me wish it was winter again.
    http://www.ultimatecarpage.com/forum/showthread.php?t=31695
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  2. #17
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    Use brakes to slow down in all cases.
    Engine braking is only useful in a RWD if you want to adjust weight transfer.
    IN a FWD you're as well braking Just do it properly - ie sufficient to slow as required and NOT lock the wheels.
    Engine braking is fine for saving fuel (in a modern fuel injected car) and in trucks (because of weight). Braking systems no longer need the "protection from fade" that normal use would elicit in 1960s cars.
    Think of engine braking as gentle application of the brakes on only one set of wheels (front or rear) Using the brakes lets you use all 4 wheels - =better
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  3. #18
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    In snow, you shouldn't be in too low a gear anyway - the torque in 1st gear for example is far more likely to lead to you wheelspinning out of control than in 2nd or even 3rd, depending on the car. Most automatic / semi-auto gearboxes have "winter modes" anyway, which use higher gearing to avoid loss of control.

    As far as slowing down goes: If the conditions are that bad, you should be allowing enough distance and driving slowly enough that even a very light application of the brakes will stop the vehicle. If there's a layer of icy, slushy stuff on the road, you shouldn't be driving at "normal" speed.

    Wintery conditions are also very good at highlighting how good your car's chassis (and inherent stability) is. It was pretty telling that last time it snowed badly here, my mum's old 1999 Vauxhall Corsa was able to make it up hills that a 2001 Ford Mondeo couldn't manage.
    "This is hardcore." - Evo's John Barker on the TVR Tuscan S

  4. #19
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    wow so it's pretty dependant on driver and i guess ur right if the weather is bad, stay home. problem with downshifting to slow down is ur brake lights don't light up which can be bad. so unless ur in an open parking lot, in bad conditions don't try anything fancy! got it!
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  5. #20
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    Quote Originally Posted by h22a View Post
    i think the conditions dictate whether you need chains baddabang the F1 driver
    We have roughly 5 months on snow, thick, heavy, wet, slippery snow. I've never seen anyone rock snow chains except for plow trucks and mail trucks.

    Oh and I'll take last comment as a compliment.
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  6. #21
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    Downshifting should never be attempted before knowing the vechile your driving..
    Sometimes you can use the gears to pull up hard and step the rear out and have the car in the right Torque area to pull away hard on corners.. Or you can use the gears to pull up even faster if say a car pull in front and leaves you with no where to go..
    Before my accident i saved myself this way on the freeway not the place you expect to see a car doing 40kmph in a 100 zone with small if no traffic.. Used my gears to aid my braking and missed hitting the rear of the clown..
    But i know my car well enough to know it's limits and speed to achieve the downshifts.. Best thing is to learn that then try it cause last thing you want to do is lock the rear up dropping to many gears at once.
    "Just a matter of time i suppose"

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  7. #22
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    Quote Originally Posted by coolieman1220 View Post
    yup wet slushy snow! that even if you use ur brakes, eventually ur ABS kicks in cause u have no traction, its happened here in NYC
    The whole point of ABS kicking in is to prevent you from losing all traction because your wheels locked up and are sliding instead of rolling.

    ABS, if used properly, ensures that your wheels do not lock up and slide by pumping the brakes for you. The correct way to use ABS is to stand on the brakes *HARD* and let the system pump the brakes. Pumping the brakes yourself defeats the whole purpose of ABS.

    On the other hand, ABS does not do anything which a skilled driver can not do in a car which has the same braking system but without ABS - pump the brakes for himself or herself.

  8. #23
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    Quote Originally Posted by Aloser View Post
    The whole point of ABS kicking in is to prevent you from losing all traction because your wheels locked up and are sliding instead of rolling.

    ABS, if used properly, ensures that your wheels do not lock up and slide by pumping the brakes for you. The correct way to use ABS is to stand on the brakes *HARD* and let the system pump the brakes. Pumping the brakes yourself defeats the whole purpose of ABS.

    On the other hand, ABS does not do anything which a skilled driver can not do in a car which has the same braking system but without ABS - pump the brakes for himself or herself.
    Actually, that's incorrect. ABS systems pump the brakes FAR faster than any human ever could. Furthermore, modern systems are able to adjust the braking to individual wheels based on the available grip using Electronic Brake force Distribution. Combine that with an Electronic Stability Programme and Emergency Braking Assistance and a human can't even begin to match the sophistication of the system.

    However, I have found that many ABS systems are set to trigger too early and therefore don't hold the car at the optimum point for scrubbing off the most speed....but that's down to the setup.
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  9. #24
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    Quote Originally Posted by coolieman1220 View Post
    So today as I walked home, it was a little wet and i was wondering to myself about downshifting vs. braking. Conventionally, brakes will slow you down much faster then downshifting and downshifting isn't too good for your car's tranny so i've heard. So say you're driving in slush or snow, bad conditions. if you step on your brakes by the time ur tires try to grip and ur ABS tries to stop lock up it takes forever for you to stop. Now in this situation if you were to downshift would you slow down faster because you use the engines power which slows the car down but could that lead to locking up the wheels and skidding?

    Basically my question is, in terrible traction conditions, would downshifting cause ur tires to lock up and or be better then applying brakes.

    Thank you and i hope to look forward to yet another interesting discussion!
    Downshifting should be seamlessly smooth to the point it shouldn't be noticeable at all.

    That's why some cars like the 370Z have rev control that rises revs when downshifting.

  10. #25
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    Quote Originally Posted by Clivey View Post
    Actually, that's incorrect. ABS systems pump the brakes FAR faster than any human ever could. Furthermore, modern systems are able to adjust the braking to individual wheels based on the available grip using Electronic Brake force Distribution. Combine that with an Electronic Stability Programme and Emergency Braking Assistance and a human can't even begin to match the sophistication of the system.

    However, I have found that many ABS systems are set to trigger too early and therefore don't hold the car at the optimum point for scrubbing off the most speed....but that's down to the setup.
    Your statement relies upon an assumption that pumping faster is automatically better as determined by a measurable decrease in stopping distance with faster pumping of the brakes. Faster pumping and / or additional sophistication is of little use if it does not result in shorter stopping distances under real life conditions when it counts. Your second statement seems to indicate that this rarely the case.

    I have heard of anecdotal evidence, some in other threads on this site, that skilled drivers have turned in shorter stopping distances in non-ABS equipped cars than in ABS-equipped versions of the same car.

    Threshold braking, which is the most effective braking technique, may be viewed as a limiting case of pumping the brakes where the rate of pumping is greatly reduced. The brakes are applied until a point is reached which is just shy of locking the brakes. Brake pedal pressure is modulated as necessary to remain at the point where the brakes are just shy of locking up.

    The primary advantage of ABS is that it is designed to take advantage of the natural reactions of an unskilled driver to slam on the brakes hard and to hold the pedal down even after the brakes have locked up and the car has started to slide.

    In my opinion, the description of "unskilled driver" applies to more than half of all drivers on the road. I do not make any claims to being among the most highly skilled of drivers. I stay out of trouble by staying home in foul weather as much as possible and by driving more slowly and cautiously when I must drive in foul weather.

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