Snow driving observations

[JExpedition07]

So I’m genuinely curious if anyone else has noticed this. When the road is super snowed up and icy has anyone else noticed braking in 4x4 High is better than in 2 high or 4x4 Auto? I’ve always subscribed to the theory 4WD only helps you accelerate but I’m noticing braking is better in 4x4 than other modes. This is over 2 days of driving. When I say this I mean ABS doesn’t seem to need to kick in as much. 4H has performed the best in this snow storm overall, the only downfall is the front end binding with tighter turns.

 

[07navi]

So I’m genuinely curious if anyone else has noticed this. When the road is super snowed up and icy has anyone else noticed braking in 4x4 High is better than in 2 high or 4x4 Auto? I’ve always subscribed to the theory 4WD only helps you accelerate but I’m noticing braking is better in 4x4 than other modes. This is over 2 days of driving. When I say this I mean ABS doesn’t seem to need to kick in as much. 4H has performed the best in this snow storm overall, the only downfall is the front end binding with tighter turns.

You're right, it is better.

 

[JExpedition07]

Turns out 4WD does indeed help you stop folks

 

[plumcolr]

It's logical, in 4wd all four wheels are locked together, thru the respective front and rear diffs, so if one wheel should lose traction the other 3 would provide some control over that wheel, not letting it lock up or spin freely. That wouldn't happen in awd or 2h as there is no solid coupling between front diff and rear diff. OTOH, sharp turns in 4wd on a slippery surface is guaranteed to make one or more wheels slide. Fine in snow, not so good on plowed slippery road.

 

[LokiWolf]

Yes, the additional drag of the diffs, axles, and the Trans also being connect to the front will add additional “Engine braking”. It is why in 4A you can feel it, regardless if it is sending power forward. Also why you lose a little MPG.


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[JExpedition07]

Found the explanation on why braking is better in 4x4. The front and rear driveshafts are locked 50/50 and MUST rotate at the same rate in 4x4 High, therefore brake force applied to the front wheels is also applied to slowing the rear wheels via the driveshaft in this locked state and vice versus. All wheels are forced to slow at the same rate now vs the different rates allowed normally.

 

[LokiWolf]

Not seeing where this has anything to do with anything.

It allows you to use Engine braking on all 4 wheels without using actual brakes. Allowing you to come to a more controlled stop.

Driving AWD vehicles fast on the track requires different techniques because of this phenomena.

Engaging with you is pointless...most of us really don’t care what you think. What ever we say will be wrong...and you will find a way to disagree. Have a good evening.


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[LokiWolf]

Not true
Why are you talking about not using actual brakes, controlled stop, AWD on a track, etc. You never make any sense to me.

Because it all factors in...the fact that you can’t understand that speaks volumes.

Trying to stop in adverse conditions is about more than just the brakes, just like on a track. When you let off the throttle on a FWD vs RWD vs AWD, the balance is different because of the set of wheels that is dragging. What can upset the balance of a car mid turn when running at the edge of grip directly correlates to driving on slippery/icy roads where you are always at the edge of grip.

Thank you for continuing to prove my point...


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[LokiWolf]

You might.

HaHaHaHaHa!!! [emoji23][emoji1787][emoji23][emoji1787] That is the funniest comment you have made so far in this thread. The Mods would laugh at you if you reported him...


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[Goofy173]

You guys are confusing 4A and 4H.

 

[JExpedition07]

You guys are confusing 4A and 4H.

I don’t think so, 4H seemed to stop smoother than 4A with less anti-lock brakes needed.

 

[Thunderbirdsport]

You guys are confusing 4A and 4H.

4A engages the front when a certain amount of slippage is detected.

4H is when the front is locked in regardless of slippage detected, and will somewhat increase the braking in slippery conditions due to parasitic "drag" on the driveline, and it also takes into play the weight shifting when brakes are applied (or throttle, for that matter).

If this were not so, a front wheel drive would handle exactly like a rear wheel drive car, in terms of braking, steering while braking, or steering while throttle.

Ever hear of torque steer, by chance.


As the saying goes, I can explain it to you but I can't understand it for you.

If you don't believe this, by all means, take your Expedition out in a few inches of snow, in say a farmer's hay field, and test this phenomenon out for yourself.


The people who say it makes no difference are people who have never driven in slick stuff.


Now the caveat here is that obviously if you're going 65 on a snow covered and packed highway, it won't make enough difference to safely stop you in the same amount of space/time as it would on dry pavement.


One last example....cars such as the Skyline GT-R....those models that have the AWD system....they're visibly faster than the the same car with just RWD, all other things being the same.

I don't know how else to explain this...

 

[07navi]

I don’t think so, 4H seemed to stop smoother than 4A with less anti-lock brakes needed.

That's true because as you pointed out; they all lock up evenly in 4h.

 

[07navi]

4A engages the front when a certain amount of slippage is detected.

4H is when the front is locked in regardless of slippage detected, and will somewhat increase the braking in slippery conditions due to parasitic "drag" on the driveline, and it also takes into play the weight shifting when brakes are applied (or throttle, for that matter).

If this were not so, a front wheel drive would handle exactly like a rear wheel drive car, in terms of braking, steering while braking, or steering while throttle.

Ever hear of torque steer, by chance.


As the saying goes, I can explain it to you but I can't understand it for you.

If you don't believe this, by all means, take your Expedition out in a few inches of snow, in say a farmer's hay field, and test this phenomenon out for yourself.


The people who say it makes no difference are people who have never driven in slick stuff.


Now the caveat here is that obviously if you're going 65 on a snow covered and packed highway, it won't make enough difference to safely stop you in the same amount of space/time as it would on dry pavement.


One last example....cars such as the Skyline GT-R....those models that have the AWD system....they're visibly faster than the the same car with just RWD, all other things being the same.

I don't know how else to explain this...

Lots of observations here but it's about braking being better while in positive 4wd as opposed to 2wd and the OP already nailed the answer to that.

 

[Utah Driver]

I would agree that 4H helps during braking. It helps when you are driving cautious and in control. However, when you aren't driving cautious and in control and need to make an emergency stop or maneuver, you will lock up all four at the same time and lose the steering when in 4H. The ABS in 2H prevents the loss of steering. I admit my experience in my 16' Expedition is limited in bad weather. I am praying for some snow but this winter in Utah is very dry. Once it does though, rest assured I'll push it to limits and find out what it can and can't do. . Cheers!

 

[Aspen03]

Late to the party here but having only driven one snowy season so far in the expy it most definitely has better stopping in 4H. It took about 10 seconds to figure that out when i stopped for the first time in snow/slush and low double digit temps. It was a sunny day plus road chemicals kept it from freezing solid but it was still fairly slick and braking noticeably better once switched to 4H.

I'm interested to see how tires do this year. They have 16k more miles on them since that snow and about half the tread remaining as they had at the time.

 

[carymccarr]

It allows you to use Engine braking on all 4 wheels without using actual brakes. Allowing you to come to a more controlled stop.

Driving AWD vehicles fast on the track requires different techniques because of this phenomena.

Engaging with you is pointless...most of us really don’t care what you think. What ever we say will be wrong...and you will find a way to disagree. Have a good evening.


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This is an interesting subject that I’ve been thinking about as I’m on steep mud/dirt and snowy/icy roads almost every weekend so I’m looking at this based on the assumption that 4WD is engaged.

If a vehicle starts to slide due to engine breaking (tires moving too slowly for the speed / traction ) on a downhill grade, your only option is to accelerate or move to a higher gear.

If instead you are gently braking to control speed you can simply remove your foot from the pedal should you start to slide.

Not to mention that a slide induced due by engine braking won’t allow abs or esp to correct trajectory I don’t think...

Perhaps a dry track is scenario different but I don’t do much hot lapping in my Navi...

 

[Yupster Dog]

This is an interesting subject that I’ve been thinking about as I’m on steep mud/dirt and snowy/icy roads almost every weekend so I’m looking at this based on the assumption that 4WD is engaged.

If a vehicle starts to slide due to engine breaking (tires moving too slowly for the speed / traction ) on a downhill grade, your only option is to accelerate or move to a higher gear.

If instead you are gently braking to control speed you can simply remove your foot from the pedal should you start to slide.

Not to mention that a slide induced due by engine braking won’t allow abs or esp to correct trajectory I don’t think...

Perhaps a dry track is scenario different but I don’t do much hot lapping in my Navi...

4WD has more options to stop the slide vs 2WD I think we all agree once the slide starts it doesn't matter. Because you have to stop the slide to regain control.

 

[carymccarr]

4WD has more options to stop the slide vs 2WD I think we all agree once the slide starts it doesn't matter. Because you have to stop the slide to regain control.

Right. my point is that stopping the slide is harder if you’re sliding because of engine breaking (in 4wd or 2wd) and not “brake” braking.

 

[LokiWolf]

Right. my point is that stopping the slide is harder if you’re sliding because of engine breaking (in 4wd or 2wd) and not “brake” braking.

Excellent point, but I wouldn’t think so.

Engine braking in a 4WD/Most AWD favors the rear more than brake braking, so control is slightly better, but like you said correcting the skid requires different tactics once actual lock up occurs, if it does start to rotate. But because of the more rear biased braking, it will be less likely to rotate.

If you just want to stop, skidding will yield a shorter stop than rolling. ABS was designed to maintain control while braking without flat spotting a tire on dry pavement. Most racing ABS systems will allow a slightly amount of lockup at lower speeds. It is a fine line.


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