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post #8506 of 14761
Henrikc has very clearly illustrated the underlying principle of physics from which AWD vehicles cannot escape. Those of you who are saying that not all four wheels have equal "footing" in adverse conditions are referring to the advantage that AWD vehicles may have with respect to acceleration in such conditions, but it does not extend to either steering or braking.
post #8507 of 14761
Quote:
Originally Posted by dah328 View Post

Henrikc has very clearly illustrated the underlying principle of physics from which AWD vehicles cannot escape. Those of you who are saying that not all four wheels have equal "footing" in adverse conditions are referring to the advantage that AWD vehicles may have with respect to acceleration in such conditions, but it does not extend to either steering or braking.

One last time for the braking: straw fucking man.

Steering: don't let the real world bite you in the ass.
post #8508 of 14761
Quote:
Originally Posted by Piobaire View Post

Quote:
Originally Posted by dah328 View Post

Henrikc has very clearly illustrated the underlying principle of physics from which AWD vehicles cannot escape. Those of you who are saying that not all four wheels have equal "footing" in adverse conditions are referring to the advantage that AWD vehicles may have with respect to acceleration in such conditions, but it does not extend to either steering or braking.

One last time for the braking: straw fucking man.

Steering: don't let the real world bite you in the ass.

You certainly don't let your ignorance in a particular area stop you from opining on it. We should get together and I could give you some tips on hospital administration.
post #8509 of 14761
Quote:
Originally Posted by dah328 View Post

You certainly don't let your ignorance in a particular area stop you from opining on it. We should get together and I could give you some tips on hospital administration.

Oh, real world performance of 2WD vs. AWD drive cars is your area of professional expertise? Who knew?
post #8510 of 14761
Quote:
Originally Posted by Blackhood View Post

While what you state is true is misses the point. If you have 4 wheels on snowy roads each wheel will have a different level of traction. Thats simply because a snowy road is not a perfectly evenly spread sheet of glass. One way or another one wheel will end up with more traction than another.

With that in mind, it is obvious that being able to choose which wheel gets the power is an asset. That might not be true when driving on an ice lake because four spinning wheels vs two spinning wheels is the same, but pulling out of a junction in the snow? Even with the front wheels on ice, the back ones will still drive the car forward.
Quote:
Originally Posted by Piobaire View Post

The thing is, in real word conditions, all things are not equal. Or maybe your roads in adverse conditions share exactly the same conditions conducive to traction over 100% of its surface area? Your roads form a perfect surface such that the coefficient of friction will be exactly the same in all locations? Your roads are such that the coefficient does not change if a tire under power spins and clears some snow to make pavement contact? In the rain any oil or other materials is perfectly distributed creating an exactly equal surface for friction at all points?

Let me clarify; I'm talking purely about steering and wanted to show that the statement made earlier ("in turning 4WD or AWD is superior") is wrong.
When it comes to regaining control of the car, I agree -- 4WD/AWD can be beneficial, but that has nothing to do with steering. That related to acceleration, which is the point dah328 is trying to make as well.

And of course things are variable in the real world, but that's not relevant to demonstrating the underlying physics. We can't factor in everything, so we have to simplify and create an environment where we can get comparable results.
post #8511 of 14761
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Edited by Beckwith - 2/13/13 at 9:49am
post #8512 of 14761
Getting off topic, I saw a 458 Italia this morning in the snow covered North Shore of Long Island. I also watched a new M5 get sideways on some sandy, wet pavement. Not sure why I would see a 458 out in these conditions, maybe his AWD/4WD car was in the shop. bounce2.gif

Maybe the variable is the driver, but I had real world experience. This morning an RDX wtih AWD, GMC Acadia and my GL450 went the same way, my car was the only one not to get stuck. Was skeptical of the 4Matic after the LR4, but it has proven to be solid.
post #8513 of 14761
Quote:
Originally Posted by Beckwith View Post

Getting off topic, I saw a 458 Italia this morning in the snow covered North Shore of Long Island. Not sure why I would see a 458 out in these conditions
facepalm.gif to that driver. There's enough salt on the roads to have me think nope.



in other Ferrari news, Ferrari of Manhattan has an F12 in their showroom. It looks pretty impressive.
post #8514 of 14761

good lord, drop this 

post #8515 of 14761
Quote:
Originally Posted by Beckwith View Post

Getting off topic, I saw a 458 Italia this morning in the snow covered North Shore of Long Island. I also watched a new M5 get sideways on some sandy, wet pavement. Not sure why I would see a 458 out in these conditions, maybe his AWD/4WD car was in the shop. bounce2.gif

post #8516 of 14761
You guys are talking semantics because even dry awd only helps cornering by letting you accelerate earlier after the apex and put the power down.

Piobare seems to be talking about the entire process of a turn where you accelerate out of the apex... Yes I think awd is better.

Dah seems to be talking about a situation where every tire is under complete lateral load with no traction left for acceleration... Yes awd will do nothing there.

Yay everyone can be right.
post #8517 of 14761
I just want to remind everyone that this whole argument started because some people said it was a good idea to use snow tires when it's cold and icy out, even if you're driving an AWD vehicle. An AWD vehicle with all-seasons or summers is unsafe in cold and icy conditions. Even if you could get the AWD car moving, you'd then have very little control over braking or steering. AWD can affect steering, but only in very specific ways and conditions. Braking? AWD will not help if you have no traction. And traction can be gained only by using the right tires.

And braking is not a strawman. You are not safe if your car cannot stop.

Then the discussion veered into specific kinds of handling and how different wheel drives work, which is where we are now. And this discussion of vehicle dynamics and handling assumes that you have traction: that your tires can actually grip the ground. If you have cold, hard tires with no or random grip, then all bets are off.
post #8518 of 14761
Quote:
Originally Posted by Vickt View Post

You guys are talking semantics because even dry awd only helps cornering by letting you accelerate earlier after the apex and put the power down.

Piobare seems to be talking about the entire process of a turn where you accelerate out of the apex... Yes I think awd is better.

Dah seems to be talking about a situation where every tire is under complete lateral load with no traction left for acceleration... Yes awd will do nothing there.

Yay everyone can be right.

I don't think that's what dah was talking about. And AWD systems can help handling, but how they do so is different for different systems, because AWD is not one generic system. For example, the vaunted Audi Quattro system cannot divert 100 percent of driving torque into a single wheel, nor can it overdrive that wheel (ie. adding more torque than it is diverting) unlike Honda's SH-AWD or even the later versions of BMW's xDrive. That affects handling in a pretty major way. AWD and RWD and FWD systems all have different suspension setups and tuning so you cannot drive them the same way and expect the same results.

For track driving, AWD can put power down earlier than RWD, but that's mostly useful in the case where torque exceeds your car's traction limits at that point in time. Most AWDs will power understeer if you get on the gas too early.

Of course, this discussion assumes that you have some reasonable amount of traction: that your tires can grip the ground. If they can't, then it's all moot.
post #8519 of 14761
Wait, snow tyres are good for driving on snow?

NO SHIT
post #8520 of 14761
Quote:
Originally Posted by Piobaire View Post

Quote:
Originally Posted by dah328 View Post

You certainly don't let your ignorance in a particular area stop you from opining on it. We should get together and I could give you some tips on hospital administration.

Oh, real world performance of 2WD vs. AWD drive cars is your area of professional expertise? Who knew?

I split my time between that and maritime law.
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