[Bogdan]

Hi everybody I have a Deville 95 and wondering if engine braking-shifting in a lower gear while driving should be used when snowy slippery roads/downhills etc ? This technique would be a potential line saver in many situation when conventional breaking would not be recommended at all...

Thanks a lot!

 

[MoistCabbage]

On snow covered roads, excessive engine braking would potentially cause the front wheels to lose traction, leaving you unable to steer. ABS wouldn't be able to help you, since the engine is slowing the wheels, and not the braking system.

There is no situation in which "conventional braking is not recommended".

 

[Submariner409]

The owner's manual recommends changing to a lower gear when going down extended, steep hills - like mountainous terrain. There is no mention of using a lower gear in ice/snow - the car has Stabilitrak, ABS, and several other features that help you out in poor traction situations. There's no need to try to "make it better".

 

[ehall]

Brakes slow the wheels, then the wheels (tires) slow the car. Wheel brakes have a point, above which they drag but at lesser speed they will stop the wheel turning, resulting in a skid. You notice this in icy weather, brakes work at 15mph then lock up at 10 mph. Engine braking almost never does this, its a drag force down to a much lower speed, in fact it is forward force at low speed and tries to keep the car moving, the opposite of a hard stop.

 

[Ranger]

Engine breaking is great for coming down a steep grade like descending a mountain (drop it in 3rd and let it idle down), but on icy pavement, MC is correct. A snowy road surface could go either way. Very slick wet greasy type snow, use the brakes. On a dry gritty snow that crunches under your tires, engine braking would probably work. The deciding factor will be the amount of traction available.

 

[Submariner409]

Wheel brakes have a point, above which they drag but at lesser speed they will stop the wheel turning, resulting in a skid. You notice this in icy weather, brakes work at 15mph then lock up at 10 mph.

Remember: His car has Stabilitrak, Traction Control and ABS - a wheel (brake) will NEVER lock.

ABS "pulses" the brakes far, far faster than any human ever could - the system provides the absolute shortest stopping distance possible without entering skid conditions.

 

[amunderdog]

I use both.
I use a lower gear to keep the ground speed under control and the brakes as needed.

 

[InfomanSS]

Ranger's last statement is the key, "The deciding factor will be the amount of traction available." The amount of traction (friction) available is what really matters. Causing the tires to rotate slower AND successfully slow the vehicle takes tire/road friction. Using a lower gear usually provides a more gentler/gradual/constant force than regular braking, but it is not a solve-it-all solution.

Example: One could manually select first gear, going downhill on solid ice, the vehicle is going 35 MPH, but the tires are only turning at 25 MPH...car is skidding/sliding.

 

[basscatt]

I can't imagine ANY situation when engine braking
would be "better" than ABS brakes on icey/snowy/slippery roads -

 

[Bogdan]

Thanks a lot. As well mentioned condition of the road and traction would give the choice I think . I've drove for many years a manual transmission and I can say from my experience that engine breaking is the best first for incrementally slowing down the speed on icy slippery roads where otherwise traction would be lost on the first touch of the brakes regardless of ABS . Yes I would use conventional braking after being sure speed was reduced so skidding risk is minimum when applying conventional braking.

I've drove a lot in icy and snowy conditions but since I have this automatic I have never tried downshifting during driving as I was afraid of transmission malfunction so what I usually do is either drive like a snail or stop and then change to a lower gear depending of the road conditions ...

So I understand that downshifting while in drive in speed range of 35miles/hour wouldn't harm the transmission? Doing this only occasionally and if necessary of course...

 

[basscatt]

Thanks a lot. As well mentioned condition of the road and traction would give the choice I think . I've drove for many years a manual transmission and I can say from my experience that engine breaking is the best first for incrementally slowing down the speed on icy slippery roads where otherwise traction would be lost on the first touch of the brakes regardless of ABS . Yes I would use conventional braking after being sure speed was reduced so skidding risk is minimum when applying conventional braking.

I've drove a lot in icy and snowy conditions but since I have this automatic I have never tried downshifting during driving as I was afraid of transmission malfunction so what I usually do is either drive like a snail or stop and then change to a lower gear depending of the road conditions ...

So I understand that downshifting while in drive in speed range of 35miles/hour wouldn't harm the transmission? Doing this only occasionally and if necessary of course...

=================================
FIRST - let me reiterate -
I can't imagine ANY situation when engine braking
would be "better" than ABS brakes on icey/snowy/slippery roads -

this goes for both automatic trans or stick -
either front drive or rear drive -

with that said - keep this in mind -

BRAKES were designed to STOP the car -

a TRANSMISSION was designed to PROPEL the car -

BRAKES are a fast - cheap and easy to replace DIY project -
premium pads cost around $50 -

a TRANSMISSION rebuild runs around $3500 -

why put ANY extra wear and tear on the trans -
if there is a BETTER - SAFER - method of stopping the car -

-------------------

oh - for the record -
I also recommend AGAINST downshifting a stick-shift car -
for the sole purpose of slowing down the car -

reason being brake pads are cheaper and easier to replace than a clutch disc -

 

[ehall]

any transmission should be able to spin up to redline RPMs (not that you'd want to make a habit of redlining)

 

[basscatt]

brakes slow the wheels, then the wheels (tires) slow the car. Wheel brakes have a point, above which they drag but at lesser speed they will stop the wheel turning, resulting in a skid. You notice this in icy weather, brakes work at 15mph then lock up at 10 mph. Engine braking almost never does this, its a drag force down to a much lower speed, in fact it is forward force at low speed and tries to keep the car moving, the opposite of a hard stop.

=============================
what?

----------

any transmission should be able to spin up to redline rpms (not that you'd want to make a habit of redlining)

=========================
what?:hmm:

 

[Ranger]

Thanks a lot. As well mentioned condition of the road and traction would give the choice I think . I've drove for many years a manual transmission and I can say from my experience that engine breaking is the best first for incrementally slowing down the speed on icy slippery roads where otherwise traction would be lost on the first touch of the brakes regardless of ABS . Yes I would use conventional braking after being sure speed was reduced so skidding risk is minimum when applying conventional braking.

Are you talking front or rear wheel drive? There could be a big difference. When you first dump the clutch, the drive wheels are likely to loose traction and skid until the car slows down enough to match the wheel speed. Not a a real big deal on a RWD where they are simply trailing behind, but on a FWD, you'll loose steering capability until the vehicle speed slows down to the wheel speed. The length of time that lasts will obviously depend on the speed you are moving when you downshift as well as the road surface friction coefficient. Admittedly, this may be a bit technical and nit picky, but still a factor to take into consideration in the realm of this discussion.

 

[MoistCabbage]

If we're still talking about snowy conditions - Even though the rear wheels are trailing behind you, they can still cause you to spin if locked, even if you're not in a turn. The crown of the road or one locking and not the other is enough to get you sideways.

 

[Ranger]

Understood. I didn't want to any any more technical than I already did. Thought I might have been pushing the limits as it was.