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post #8491 of 15698
Quote:
Originally Posted by dah328 View Post

I have although it's not relevant since one does not have to do that in order to understand basic physics.

I think you are equating the idiots that try to drive too fast because they have AWD or 4WD and then lose it in a turn vs. the actual situation. Let's think about this. Two cars going 10 mph in deep snow, one RWD, one AWD, and that is the only difference between those two vehicles. They both attempt to turn. Which car a) has the better likelihood of turning or b) if a slide/skid is initiated regaining control and completing the turn?
post #8492 of 15698
Quote:
Originally Posted by Piobaire View Post

Quote:
Originally Posted by dah328 View Post

I have although it's not relevant since one does not have to do that in order to understand basic physics.

I think you are equating the idiots that try to drive too fast because they have AWD or 4WD and then lose it in a turn vs. the actual situation. Let's think about this. Two cars going 10 mph in deep snow, one RWD, one AWD, and that is the only difference between those two vehicles. They both attempt to turn. Which car a) has the better likelihood of turning or b) if a slide/skid is initiated regaining control and completing the turn?

That's precisely the situation I have in mind. Neither vehicle has an advantage because lateral traction determines the vehicles' turning capabilities and the lateral traction available to the vehicles is completely independent of the number of drive wheels.
post #8493 of 15698
Quote:
Originally Posted by dah328 View Post

That's precisely the situation I have in mind. Neither vehicle has an advantage because lateral traction determines the vehicles' turning capabilities and the lateral traction available to the vehicles is completely independent of the number of drive wheels.

Did not mean to thumbs this...

Have you ever gassed a 4/AWD when it starts to slip in this scenario? The steering tyres tend to dig in and bite, as they are powered, thus providing traction. With a RWD the ass end slides out or pushes the car in a vector not equal to the one set by the steering tires. I've experienced this probably thousands of times in my life. By having power to the front wheels the 4/AWD is superior in gaining traction in a way the RWD simply cannot.
post #8494 of 15698
yjy4esu9.jpg

Friend spotted this today......lol
post #8495 of 15698
Modern AWD's have the ability to route power to whichever wheel(s) of the four that have the most traction. How's that not an advantage over 2wd, where advanced TC systems can do the same thing but only on two drive wheels?
post #8496 of 15698

https://www.youtube.com/watch?v=wdiF-BxPSH0

 

Quote:
Originally Posted by dah328 View Post

I have although it's not relevant since one does not have to do that in order to understand basic physics.

 

 

We often agree, dah, but I think you may be belaboring a mistaken assumption. If the physics is basic, state the principle you question.

 

If you have two cars, each say 200hp, and one AWD and the other 2WD, it is manifest that the vehicle with AWD will be dividing said 200hp in some manner between some subset of the four tires. This should make it superior to FWD, where the two tires that are dividing all the power also have to cope with steering loads. Handling is a vague term, but the fact that the steering wheels have less torque going to them should make them less inclined to slip than if they were handling all the torque. RWD cars have a similar issue, as they are inclined to oversteer. Reducing the torque to the rear wheels should raise the oversteer threshold. There's also the weight transfer issue.

 

So, on balance, AWD does handle better, if you define better as requiring more severe conditions in order to run off the road than a comparable 2WD car driven by the average driver (and excluding braking). On the other hand, I think that a better driver can learn to drive a RWD car better than the comparable AWD car because its tendency to oversteer can be exploited -- but I wouldn't call that handling 'better'.

 

~ H

post #8497 of 15698
How about we stop arguing over which drive-train is better for traction and everyone accept the fact (yes, fact) that by placing your car's floor mats (ideally rubber) under your tires, you will escape the dreaded no-traction trap with great ease and finesse.

teacha.gif
post #8498 of 15698
Quote:
Originally Posted by HRoi View Post

Modern AWD's have the ability to route power to whichever wheel(s) of the four that have the most traction. How's that not an advantage over 2wd, where advanced TC systems can do the same thing but only on two drive wheels?

This. Its an obvious advantage unless you define handling by 'getting her sideways'.

Quote:
Originally Posted by Huntsman View Post

We often agree, dah, but I think you may be belaboring a mistaken assumption. If the physics is basic, state the principle you question.

If you have two cars, each say 200hp, and one AWD and the other 2WD, it is manifest that the vehicle with AWD will be dividing said 200hp in some manner between some subset of the four tires. This should make it superior to FWD, where the two tires that are dividing all the power also have to cope with steering loads. Handling is a vague term, but the fact that the steering wheels have less torque going to them should make them less inclined to slip than if they were handling all the torque. RWD cars have a similar issue, as they are inclined to oversteer. Reducing the torque to the rear wheels should raise the oversteer threshold. There's also the weight transfer issue.

So, on balance, AWD does handle better, if you define better as requiring more severe conditions in order to run off the road than a comparable 2WD car driven by the average driver (and excluding braking). On the other hand, I think that a better driver can learn to drive a RWD car better than the comparable AWD car because its tendency to oversteer can be exploited -- but I wouldn't call that handling 'better'.

~ H

Mostly agree. His premise only defines handling in very specific (read narrow) terms. Its a broader concept and I 2nd the call for an explanation on the physics.

Not sure about a better driver and RWD, though. Maybe too much Top Gear and running sideways? I can't see too many situations on the road where this idea of inducing oversteer is necessary. But, should I be proven wrong, in most AWD cars you can turn these systems off and run the rear wheels.

For me I like a neutral handling car.
post #8499 of 15698
Quote:
Originally Posted by Piobaire View Post

As for braking it does not. As I never maintained it did this is a straw man. This however is not the complete summation of the situation, now is it? There is acceleration (4 chances vs. two) and even in turning 4WD or AWD is superior. Have you ever driven such a vehicle in snowy conditions?

Let's do a small physics experiment here.

Which box will slide faster? The coefficient of friction is the same, they have the same mass and the same incline. (I do apologize for the terrible handwriting)
N is the normal force, exerted from the plane. G is the gravitational force, and R is the resistance. The only difference is the color.

It would be reasonable to think that both will behave the exact same way, right? Yes. They will.

It's the same concept with steering and braking traction. When talking about traction on a slippery surface, other things equal, 1WD, RWD, 4WD or 3WD does not matter. What matters is the coefficient of friction between the tires and the surface. When two identical cars, with the same center of gravity, same weight distribution etc, and the only difference being RWD/4WD, they'll behave exactly the same.
post #8500 of 15698
Quote:
Originally Posted by henrikc View Post

Let's do a small physics experiment here.

Which box will slide faster? The coefficient of friction is the same, they have the same mass and the same incline. (I do apologize for the terrible handwriting)
N is the normal force, exerted from the plane. G is the gravitational force, and R is the resistance. The only difference is the color.

It would be reasonable to think that both will behave the exact same way, right? Yes. They will.

It's the same concept with steering and braking traction. When talking about traction on a slippery surface, other things equal, 1WD, RWD, 4WD or 3WD does not matter. What matters is the coefficient of friction between the tires and the surface. When two identical cars, with the same center of gravity, same weight distribution etc, and the only difference being RWD/4WD, they'll behave exactly the same.

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.
post #8501 of 15698
Quote:
Originally Posted by henrikc View Post

Let's do a small physics experiment here.

Which box will slide faster? The coefficient of friction is the same, they have the same mass and the same incline. (I do apologize for the terrible handwriting)
N is the normal force, exerted from the plane. G is the gravitational force, and R is the resistance. The only difference is the color.

It would be reasonable to think that both will behave the exact same way, right? Yes. They will.

It's the same concept with steering and braking traction. When talking about traction on a slippery surface, other things equal, 1WD, RWD, 4WD or 3WD does not matter. What matters is the coefficient of friction between the tires and the surface. When two identical cars, with the same center of gravity, same weight distribution etc, and the only difference being RWD/4WD, they'll behave exactly the same.

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?
post #8502 of 15698
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.

If you are accelerating from a corner in RWD there is a weighted wheel and unweighted wheel, the unweighted wheel will provide less of an opportunity to grip and accelerate. With AWD, there are 2 weighted wheels on the outside able to transfer power and shift power away from an unweighted wheel wanting to break away and produce wheel spin.
post #8503 of 15698
I think you're agreeing with me, aren't you?
post #8504 of 15698
Quote:
Originally Posted by Blackhood View Post

I think you're agreeing with me, aren't you?

Yes, I am.
post #8505 of 15698
Quote:
Originally Posted by gort View Post

yjy4esu9.jpg

Friend spotted this today......lol

stupid propaganda machine
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