[supermatt]

AWD != 4x4. AWD + traction control absolutely helps driving on snow and ice with appropriate tyres.

If you are driving with summer tyres on ice, then of course you are going to be skittering all over the place.

When going downhill on ice, again your tyres are going to make ALL the difference. You shouldnt be trying to stop going downhill on ice anyway. You should be descending at a constant and controlled speed.

[alkonaut]

I think "AWD" today is used to mean "anything that isn't 2WD". So whether it's a full time 4x4 or something that is mostly-fwd-but-rwd-when-slipping or something else isn't part of the nomenclature. It simply means "something more than 2WD at least some of the time". There has been an endless debate as to whether 4WD or AWD are the same or different, whether only "symmetric" or "full time" counts as one or the other. But these days with hybrid drives, traction control shifting drive front/back etc., it's just too complex to keep apart any more.

[supermatt]

Not really - AWD is effectively non-braking traction control by varying the power distribution to each axle (and on some modern electric drivetrains, each wheel). 4wd provides constant power to both axles.

[alkonaut]

I think of it more as an outdated distinction. First of all with motors on each wheel and no communication between front/rear in many cases, the distinction becomes blurry.

Further many manufacturers have names like “AWD” (volvo and others) or “4matic” (MB) or “4motion” (VW) to label their take on more-than-2wd, whether or not their variant is awd or 4WD (or both) in the traditional sense. Some "AWD" models will be electric with 1 motor per axle, or 3 motors (1 front 2 rear) etc. Some others are ICE with traditional drive shaft to the rear wheel axle, which in some cases will drive 50/50 and in some cases variable. Others still are hybrids wth no prop shaft but instead a rear electric motor etc.

[supermatt]

Its not outdated. There may be multiple variations on AWD (as i mentioned, some can vary power to individual wheels, rather than just the axles), but 4WD (or 4x4) is categorically not AWD.

[alkonaut]

Doesn't traction control further blur that? Given that traction control is now required almost everywhere, and involves cutting power to individual wheels (Not like ESP using brakes), at what point does traction control cutting power to individual wheels or axles dynamically in a 4x4/4WD system make it an "AWD" instead?

Perhaps those vehicles that use 4x4 in the tradtional sense are such that you have to engage it and that effectively cuts also any traction control - and then you disengage for normal driving?

[supermatt]

Traction control on an AWD system can be composed of power management (overall torque output), power distribution (how much power goes to each axle/wheel) and braking (slowing down individual wheels).

Traction control on a 4WD can only consist of power management and braking, because there is no way to vary the distribution (otherwise it would be AWD, not 4WD).

There are some systems that under certain conditions will switch from 2WD to 4WD. Those systems are NOT considered AWD and dont have the benefits thereof.

FYI, ESP (Electronic Stability Program) is just a brand term for an ESC (Electronic Stability Control) which covers both TCS and ABS. When people talk about "traction control" they usually mean the entire ESC subsystem.

[brookst]

I think there is more nuance here. A 4x4 with a locked center diff and open front and rear diffs acts just like many AWD implementations.

That same 4x4 with limited slip diffs on front and/or rear is just like other AWD implementations.

And that same 4x4 with locked front and/or rear diffs is just like yet other AWD implementations.

[supermatt]

> A 4x4 with a locked center diff and open front and rear diffs acts just like many AWD implementations.

Thats simply not true. It wouldnt be AWD if it cant adjust the power supplied to each axle. Thats the primary distinction.

[sandworm101]

>> First of all with motors on each wheel and no communication between front/rear in many cases, the distinction becomes blurry.

Which cars have motors on each wheel? That is maybe 0.01% of vehicles on the road. (Electric busses?) And even then, AWD/FWD distinctions can matter in how those motors interact. Electric or IC, so long as power is delivered through four wheels there will be different styles and techniques for balancing that power for whatever reasons occur at a particular time.

[supermatt]

Nothing yet, but the next porsche electric drivetrain supposedly will:

https://newsroom.porsche.com/en/2019/technology/porsche-engi...

[meetingthrower]

Agree. We have a Tacoma that has 4WD and it is the absolute dumbest implementation. Contrast that to the Subaru with AWD and it is a completely different driving experience. We go with studs on the Tacoma for that reason, and get by with regular snows on the Subie.

[Tor3]

It doesn't mean any difference when you're trying to slow down downhill. As you're saying, "your tyres are going to make ALL the difference." Which is exactly what I said - 4x4 or AWD doesn't help anything with that.

[supermatt]

Well actually... 4x4 is worse for going downhill on ice. If one axle loses traction (which would be much more likely on summer tyres), the other can initiate a slide.

This is the exact reason people dont like 4x4 on ice. AWD (usually) lessens the problem - which is why i said they absolutely help with the correct tyres.

And again - DONT SLOW DOWN when going down hill. Your brakes WILL lock a wheel and you WILL slide. Slow down BEFORE you go downhill. If you havent experienced this truth, then you havent driven downhill on ice (which is preferable).

[bombcar]

Yeah 4xAWD (let’s piss everyone off) helps maintain action when you’re driving IN the snow (you have a slightly better chance of not getting stuck if you can power all your wheels and have appropriately calibrated antislip).

But losing control because of ice can happen no matter how many driven or traction control wheels you have. And all wheels are basically skis when you’re skidding at 90° to the direction of travel. In fact, in some skids front wheel drive will be the best as at least you have a chance of powersteering out.

The real trick is to not start the skid at all. Sloooooooow down before you’re driving sideways.

[supermatt]

> In fact, in some skids front wheel drive will be the best as at least you have a chance of powersteering out.

Yep, this is actually why AWD is (usually) better than 4WD, because it can drive the single axle, treating it as a 2WD.

[quickthrowman]

Why would you try to slow down (with your brakes) while going downhill on a snowy road? That is the worst possible thing you could do. Go slower at the top of the hill or let off the gas to reduce your speed.

[adql]

> AWD != 4x4. AWD + traction control absolutely helps driving on snow and ice with appropriate tyres.

Too late buddy. The way manufacturers abused AWD, 4WD and 4x4 terms they can mean anything now

[supermatt]

Which manufacturer is using AWD incorrectly?

[falcolas]

Dodge. They call their Charger implementation AWD, but it’s RWD only until a slip, then it engages the front axel.

They fooled me, and it drove like crap on snow. Always wanted to slide.