Driving on ice or snow experiences, or tips

[alpg88]

weight goes both ways, if it help traction, it hurts braking

 

[PhotonWrangler]

weight goes both ways, if it help traction, it hurts braking

Very true! More weight = more forward momentum that needs to be overcome when trying to stop.

 

[KITROBASKIN]

Inherent issue with unloaded pickups is significantly lighter on the rear, messing up handling, right? I used to place sand bags in the back of our old truck during the most dangerous time of winter, knowing that the arroyo material might come in handy spreading on an icy patch that was stopping a damsel in distress or, more likely a distressed dude.

This 2019 Tacoma has electronic decision making algorithms baked in with the brakes and such. Along with an aluminum open shell over the bed and a heavyish restaurant type open hole rubber mat for the dogs, it is concerning in the sense that I still kind of don't know where the edge of traction starts to fail, that truck is so sure-footed.

But don't kid yourself about the effect of increased weight, lighter rear end, and higher center of gravity putting the hurt on all you hold near and dear…

Good gracious though, even With adaptive radar controlled cruise control I would not activate that on the icy path to treachery.

 

[JustAnOldFashionedLEDGuy]

weight goes both ways, if it help traction, it hurts braking

This is an incorrect or potentially incorrect assumption. It depends on whether braking is traction limited or brake force limited. In winter, often the braking limitation is traction and just like weight gives you more acceleration due to added traction, the exact same mechanism gives you better stopping too. If the weight is cutting through snow, the benefit can be greater than the weight. Obviously there are many variables, but a generic statement if it helps traction it hurts braking is simply not true. As well, by putting weight over the rear wheels, it reduces the impact of weight shift during braking and can improve handling during breaking.

 

[KITROBASKIN]

An old timer (retired electrical engineer used to work at Sandia Labs) believed that narrower tires would get grip through the snowfall to the road surface better than wide, floating tires.

 

[rwolfenstein]

Back in the day I bought a jeep and thought that ice or snow could not stop me. I had crap tires, which were well worn street tires. I went up to the back wood roads around a place called Hockinson and there was still snow on the ground. I was doing 40 mph with a ditch on my left and a downward slope on my right. I went to take a curve and spun the jeep in a circle. I admit, I almost crapped myself but my training I had from the agency I volunteered at allowed me to correct the spin out and gain control. After that, you learn a couple of things. 1 have good tires and check them often for treadwear. 2 four wheel drive will get you going and doesnt help you stop. 3 only drive as fast as the elements allow and finally 4, arrive alive.

 

[JustAnOldFashionedLEDGuy]

An old timer (retired electrical engineer used to work at Sandia Labs) believed that narrower tires would get grip through the snowfall to the road surface better than wide, floating tires.

This is very much the case. Always good to go down a width (or two) for your winter tires if you are going to regularly be in deeper snow. Even if you don't go down to the road surface, you are compacting the snow and providing a more stable traction surface. Of course, there is the alternate of balloon tires and floating on top, like fat bikes, and the tread the only thing penetrating, but that is not practical for cars.

 

[Chicken Drumstick]

four wheel drive will get you going and doesnt help you stop.

Not 100% true, but certainly not to be taken lightly. Stopping distances will massively increase in slippery conditions. But a 4x4 can have an advantage. If it is along the lines of a proper 4x4 with a transfer case or lockable centre diff, rather than a Haldex style unit.

Using 4wd will essentially lock the front and rear axles together. Under braking this means you get 50:50 brake bias. I.e. both axles will get the same braking force.

For normal road use, cars will generally have a front brake bias (maybe 70:30), because on a normal grippy surface you get a massive weight transfer to the front of the vehicle. So you need more braking effort on the front axle. Likewise the rear will lift, meaning you need less braking effort else the rears will lock up sooner (or induce ABS).

In the snow/ice a front biased brake setup means you ABS will kick in way too early reducing your overall braking effort. Using the transfer box to induce 50:50 brake bias will make the brakes much more effective. The same vehicle may be able to stop a car length or two sooner if used in 4wd.

 

[alpg88]

Not sure about UK, but in usa very few suvs have such locking diffs, most have positrack, and only in the rear, most of them are automatic, only real off roaders have those, and very few people here know what they are and how to use them.
My 2021 passport has electronic control awd, i have 4 modes, normal, snow, mud sand, i can see how torque is distributed on the screen, but not breaking force. normally it is fwd, but in snow or sand mode torque distributed 50/50, however i have no idea if it locks differentials. probably not. it is not a real suv, but a tall station wagon, with some off road capability.
in any case in snow, chains/cables will do more good than locking diffs, no diff locks will stop your cars from sliding sideways, but chains will

 

[fulee9999]

Not sure about UK, but in usa very few suvs have such locking diffs

to be honest without any googling I can only name two factory cars that have actual locking diffs - where you can lock both front, back and front-to-back as well -, the Mercedes G class, and the Jeep Rubicon edition. Most 4x4 or 4WD or AWD cars I've seen can lock the rear ( if even that ).

 

[JustAnOldFashionedLEDGuy]

Not 100% true, but certainly not to be taken lightly. Stopping distances will massively increase in slippery conditions. But a 4x4 can have an advantage. If it is along the lines of a proper 4x4 with a transfer case or lockable centre diff, rather than a Haldex style unit.

Using 4wd will essentially lock the front and rear axles together. Under braking this means you get 50:50 brake bias. I.e. both axles will get the same braking force.

For normal road use, cars will generally have a front brake bias (maybe 70:30), because on a normal grippy surface you get a massive weight transfer to the front of the vehicle. So you need more braking effort on the front axle. Likewise the rear will lift, meaning you need less braking effort else the rears will lock up sooner (or induce ABS).

In the snow/ice a front biased brake setup means you ABS will kick in way too early reducing your overall braking effort. Using the transfer box to induce 50:50 brake bias will make the brakes much more effective. The same vehicle may be able to stop a car length or two sooner if used in 4wd.

Your knowledge of ABS is perhaps out of date. I doubt there is an ABS system out there any more that is not at least 3 channels, and many now are 4 channel. In a 3 channel system, the two front wheels are controlled independently, and the rears together. With a 4 channels, all 4 wheels are controlled separately. Even a 3 channel system would work better than what you describe, and a 4 channel would work even better still. What you describe is essentially a single channel system and that would be very ineffective, either with a locking differential or not.

 

[JustAnOldFashionedLEDGuy]

Traction control has replaced locking differentials for all but a few vehicles.

 

[alpg88]

Traction control has completely different function than diffs.

The traction control system (TCS) detects if a loss of traction occurs among the car's wheels. Upon identifying a wheel that is losing its grip on the road, the system automatically applies the brakes to that individual one or cut down the car's engine power to the slipping wheel.

The differential is a system that allows the drive wheels to turn at different speeds, which is required when the car is negotiating a turn. In a turn, the outside wheel must travel farther, which means it must travel faster than the inside wheels.

 

[JustAnOldFashionedLEDGuy]

Traction control has completely different function than diffs.

The traction control system (TCS) detects if a loss of traction occurs among the car's wheels. Upon identifying a wheel that is losing its grip on the road, the system automatically applies the brakes to that individual one or cut down the car's engine power to the slipping wheel.

The differential is a system that allows the drive wheels to turn at different speeds, which is required when the car is negotiating a turn. In a turn, the outside wheel must travel farther, which means it must travel faster than the inside wheels.

Before you make a funny face and correct someone, it is best that you learn the practical aspects of what you are talking about.

LOCKING differentials cause all the wheels to turn at the same speed. That matters in really rough terrain as normally a differential transfers power to the wheel with the least resistance, i.e. the one spinning. Get one wheel in the air on a normal differential, or one wheel with traction and one without, and the wheel without traction spins. In more extreme off road situations, but even in mud, or deep snow, etc. locking the differentials ensures the wheels that can have traction or still have traction actually do something.

Traction control effectively does the same thing but with normal differentials. When one wheel is slipping, traction control applies braking to that wheel stopping it from spinning and stopping it from being the wheel of least resistance. This causes torque to vector to the other wheel that is not turning giving you traction back. For non extreme conditions, it effectively performs the function of locking differentials.

We can leave viscous limited slip differentials to a different educational post.

 

[alpg88]

As i mentioned before in other threads, i'm a part owner of a repair/body shop, for over a decade, so i'm pretty confident i know how cars and its component function, i may not be able to solve every electrical problems in modern cars, we got people for that, but fundamental functions, i got down. so thanks for your input, it's been very entertaining. looking forward for your next stand up.

 

[alpg88]

 

[JustAnOldFashionedLEDGuy]

View attachment 36427

As i mentioned before in other threads, i'm a part owner of a repair/body shop, for over a decade, so i'm pretty confident i know how cars and its component function, i may not be able to solve every electrical problems in modern cars, we got people for that, but fundamental functions, i got down. so thanks for your input, it's been very entertaining. looking forward for your next stand up.

Would you like a cookie?

1) I said LOCKING DIFFERENTIALS in my first post you replied to and how they have effectively been replaced by traction control. Your response? --- To try to educate me on differentials in general, which really has nothing at all to do with LOCKING DIFFERENTIALS which when locked, guess what, are NOT really differentials any more. Your first failure.

2) My education for you on what traction control does and how it effectively performs the function of a locked differential, is absolutely, 100% accurate, and on point. Your lame call to authority does not negate my accurate answer. Failure #2.

3) Your comment about adding weight hurts breaking, in a thread about ice, was again, often wrong, at least where breaking on snow and ice is concerned. Failure #3.

For someone who has the fundamental functions down, you have some glaring holes in your knowledge of fundamental functions. I would not be using a call to authority unless I was 100% right.

Oh, your call to authority? I will see your "part repair/body shop owner", and raise you 15+ years of engineering for automotive electronics, system integration, and vehicle level test at Tier-1 suppliers including drive systems for a while.

 

[alpg88]

LOL, another pile of rubbish, you need to funny up a bit, you are getting lame.

 

[JustAnOldFashionedLEDGuy]

LOL, another pile of rubbish, you need to funny up a bit, you are getting lame.

Put up or shut up alpg88 and stop acting like an immature 9 year old. You have not been able to refute 1 thing I said. I all you do is pump your chest, but I am sure everyone else, like I, has noticed you have not added anything of value to the conversation.

 

[JustAnOldFashionedLEDGuy]

LOL you actually think i take you seriously enough to have a debate? keep talking your nonsense.

I think you have shown that you clearly are all hubris, but of little knowledge. I know it. Everyone else reading this thread now knows it. Keep digging if it makes you feel better. There is nothing to debate. These are items of vehicle design and physics, not "opinions". You have opinions that are incorrect.