[Avaley]

How would PS4s and other more versatile performance tires stack up with xDrive for all season use including light snow?

[luckylingy]

They won’t stack up at all. Below 45F performance tires’ rubber compounds become hard and slippery, whereas winter tires’ compounds are designed to remain soft in colder temperatures. Performance tires don’t have sipes to bite into ice or snow, like winter tires do. Instead, their large tread blocks grip dry pavement — or glide over frozen precipitation.

[evilalien]

Originally Posted by Avaley

How would PS4s and other more versatile performance tires stack up with xDrive for all season use including light snow?

Probably kill you faster, due to AWD overconfidence. If it is below 7C then summer rubber feels noticeably harder.

At the very least, put on all-seasons if you don't need the "extreme" cold snowflake-on-mountain tires.

[luckylingy]

Originally Posted by evilalien

… due to AWD overconfidence.

So true (as the young me, who slid his month-old Audi quattro into a parking lot stop sign). Four tire contact patches are the only thing keeping you on your intended path. AWD doesn’t come into play if you’re braking or maintaining throttle.

[evilalien]

Originally Posted by luckylingy

AWD doesn’t come into play if you’re braking or maintaining throttle.

I'm not an engineer, however I don't think that is true. When the engine is turning that axle (rather than the wheels being turned by the road), you are applying force through the contact patch in the direction the wheels are pointed. I don't know if "thrust" is the right term, but thinking of it as applying thrust in the direction both sets of wheels are pointed seems correct to me.

[luckylingy]

Originally Posted by evilalien

I'm not an engineer, however I don't think that is true. When the engine is turning that axle (rather than the wheels being turned by the road), you are applying force through the contact patch in the direction the wheels are pointed. I don't know if "thrust" is the right term, but thinking of it as applying thrust in the direction both sets of wheels are pointed seems correct to me.

Fair point. My intended point was that AWD doesn’t help deceleration or cornering when off the throttle.

[evilalien]

Originally Posted by luckylingy

Fair point. My intended point was that AWD doesn’t help deceleration or cornering when off the throttle.

I guess it depends on how much force the engine is applying when not breaking (it isn't zero), but your point is super important. Whatever is happening, unless the engine is putting power through to the wheel, all that matters is what that contact patch is doing (friction with the road surface). AWD only helps if it can get that power applied in one or more useful vectors incl when any of the other wheels are slipping but one or more isn't

Vehicle dynamics is fun. And gets complicated quickly.

[luckylingy]

Originally Posted by evilalien

Vehicle dynamics is fun. And gets complicated quickly.

… especially when you realize the shiny black pavement you’re cruising over at speed isn’t wet but frozen. And something unfolds in front of you.

The moment the s**t hits the fan is when you discover whether you made the right tire choice for the season.

[evilalien]

Originally Posted by luckylingy

… especially when you realize the shiny black pavement you’re cruising over at speed isn’t wet but frozen. And something unfolds in front of you.

The moment the s**t hits the fan is when you discover whether you made the right tire choice for the season.

Indeed. I've had a few close encounters, saved care of AWD and winter tires.

One time, taking a corner through an intersection, I was able to hold my line. The other care beside me couldn't, but with AWD + Dunlop WinterSports I was able to not only control and evade collision but accelerate out of the turn to get away from the idiot.

Another, icy downhill road, idiot in a pickup truck though they were invincible and came up behind me really quickly to bully me out of the way. What they weren't was "in control", fortunately I was and was able to get out of the way.

Belief is irrelevant. Physics always wins.

[luckylingy]

evilalien, I see you’re coming from an M240 xDrive. It’s a demon in the snow, with the right tires! Here’s my M235 xDrive’s maiden arrival home, after driving a half-mile through 15” of virgin powder (plus 15 miles of blizzard conditions) ..

[luckylingy]

… and a calmer, late-winter day …

[evilalien]

Originally Posted by luckylingy

evilalien, I see you’re coming from an M240 xDrive. It’s a demon in the snow, with the right tires! Here’s my M235 xDrive’s maiden arrival home, after driving a half-mile through 15” of virgin powder (plus 15 miles of blizzard conditions) ..

It holds it's own

My AWD-saved-my-ass stories are from a WRX and an STI, though. The STI was a snow devouring monster.