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  1. #1
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    Downshifting vs. Braking

    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!
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  2. #2
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    I suppose if you are terrible at downshifting it could happen. I've seen 16 y/o noobsauc3's chirp the tires wile stopping on dry pavement.
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  3. #3
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    I wouldnt mind being called a n00bsauc3 if i could have a car with a manual trans.
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  4. #4
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    Well you shouldnt be trying to brake at the maximum capability of the car, meaning the ABS shouldnt be anywhere near trying to activate.

    I'd say though in slippery conditions, anyone other than a professional would more likely skid the car using engine braking than conventional braking, as they'll be getting sudden jerks through the car as they go through each lower gear, each one unsettling the car. If you know what youre doing you can do engine braking without unsettling the car, but having never compared double de-clutching to simply letting the synchros do their job, i wouldnt know how they compare to how effectively they slow you down.
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  5. #5
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    Downshifting. If you downshift properly it won't do any damage to the transmission and if you do it slowly and preferably double clutch it gives you much more traction in the wet. A really good driver knows that brakes are really for slowing down the RPMs in order to downshift properly and not immediately stopping.

  6. #6
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    what is this... snow?
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  7. #7
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    Quote Originally Posted by whiteballz View Post
    what is this... snow?
    I'll UPS some to you in a couple months


    BTW ABS is for the weak.
    John says:
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  8. #8
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    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

    now what about downshifting in a car with a semi auto. for instance a G35 u can downshift the car, it won't let you do it early but when it can it will does that damage and if u do it and ur car starts to skid could traction control do anything? the enigne isn't gettin throtttle its trying to slow down but is spinning fast
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  9. #9
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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

    now what about downshifting in a car with a semi auto. for instance a G35 u can downshift the car, it won't let you do it early but when it can it will does that damage and if u do it and ur car starts to skid could traction control do anything? the enigne isn't gettin throtttle its trying to slow down but is spinning fast
    Imagine that. Snow in NYC.
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  10. #10
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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.

  11. #11
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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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  12. #12
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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.

  13. #13
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    One thing I can see in your G35 example is that if you do a downshift instead of braking in that condition, all that is going to affect if the rear wheel, which is more likely to cause instability issue in bad condition. Though in an auto G35, as you noted it won't let you downshift when it doesn't get the right rpm, which probably minimize the chance of it being jerky on the downshift to upset the balance of the car....Personally in my G35 in winter(auto also) I do downshift first before I get on the brake, though to note this is in no emergency condition. As in winter anyway I usually don't try to gamble on making any corner at any significant speed....
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  14. #14
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    Traction control wont do anything if your brakes have locked up under braking. You need things like ABS, EBD and stability control for that which can actually electronically monitor the brake loading.

    Also, unless youve got snow chains or studded tyres, which it sounds like you definately need for the conditions, you shouldnt be on the roads. Even then, you need to allow much longer braking distances.
    Last edited by fpv_gtho; 08-20-2007 at 09:32 PM.
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  15. #15
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    You definitely don't need snow chains or studded tires for slush.
    John says:
    so i had to dump acid into the block tank today
    i'm afraid to fap
    cause i got it on my hands

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