Best vehicle for bad weather conditions

[JCH13]

Wait, the links you provided that I replied to do? No. Wow. I can find more links if you want but not worth discussing it with you. Have you driven an Acura SH-AWD system? No. And I love how your new links reference 4WD.

http://www.caranddriver.com/feature...ll-climb-and-straight-line-performance-page-2

http://www.caranddriver.com/feature...at-price-traction-braking-and-handling-page-3

Bro, do you even read? Or think? Testing, numbers, quantifiable results. Well-thought-out analysis and conclusions based on those results.

Please find me a semi-technical article from a reliable source with at least some hand-waving at the scientific process and I'll believe you. Find me any rational expatiation about how being able to power all four wheels increases the tires' grip and I'll believe you.

Consumer Reports:

http://www.consumerreports.org/cro/...cember/cars/winter-driving/overview/index.htm

A lot of drivers get in trouble because they think that AWD or 4WD lets them go as fast as they want on slippery roads. In fact, although the systems provide maximum traction when traveling straight ahead, they provide no added benefit when braking or cornering. For aid when braking, make sure you have an antilock braking system; for cornering, you need electronic stability control.

The most un-biased commercial source possible. What more information do I need to provide to convince you?

 

[slatr]

Consumer reports need to accelerate hard in a corner in an STI and then try it again in a Mustang or RWD car before making such a broad statement.

A lot of drivers get in trouble because they think that AWD or 4WD lets them go as fast as they want on slippery roads. In fact, although the systems provide maximum traction when traveling straight ahead, they provide no added benefit when braking or cornering.

 

[JCH13]

Consumer reports need to accelerate hard in a corner in an STI and then try it again in a Mustang or RWD car before making such a broad statement.

A lot of drivers get in trouble because they think that AWD or 4WD lets them go as fast as they want on slippery roads. In fact, although the systems provide maximum traction when traveling straight ahead, they provide no added benefit when braking or cornering.

If you read the article you would know that this statement is clearly made in reference to winter driving conditions, as it was in my post.

 

[ND40oz]

Part of the problem is that car and driver article is from 14 years ago when awd systems were much different and torque vectoring systems weren't in use.

Here's quick explanation of the ZF system.

http://www.popularmechanics.com/cars/news/4225886

German transmission and driveline company ZF has also developed a torque-vectoring system, called Vector Drive—and it’s ready for volume production in all-wheel and rear-wheel drive vehicles. The system distributes drive torque individually to each of the rear wheels, generating a yaw movement around the vertical axis. This improves both cornering performance and vehicle stability in less-than-ideal road conditions. When driving straight, the torque vectoring rear axle behaves like an ordinary open differential. Drive torque is distributed equally to the wheels. Torque is only distributed individually along both halfshafts on an axle during cornering, controlled by an electromechanically actuated multi-disk brake. The ZF system also generates wheel differential torque independently of the drive torque. When cornering through a downhill section off the throttle, the outer wheel receives more drive torque than the inner wheel, allowing crisper turn-in. The gears of the planetary gearset don’t turn when driving straight, so the system saves fuel too. The torque-vectoring drive also acts like a positive-traction or locking differential on dry or uneven traction startups, with torque going to the wheel with higher friction potential.

 

[JulesMaximus]

Like this?



Or this article?



You are CLEARLY falling victim to 'over-confident driver' syndrome. You should NOT be driving faster because you have AWD, you CANNOT stop faster than a 2WD vehicle. You are a danger to other people and yourself if you honestly think you can drive faster and turn better in the snow because you have AWD.

This is so true it's not even funny. I remember when I was growing up in upstate NY in the winter, during a snowstorm the majority of vehicles in the ditch were 4x4 trucks or SUVs. Granted there are situations in which any vehicle would slide off the road (black ice-nothing will help you with that short of studded snow tires).

 

[desy]

I luvs a FWD RWD AWD/4WD whine off
AWD > FWD > RWD in winter, tires and nanny systems being equal.
If I lives where I needed ground clearance hills and turns with winter I would get AWD/4WD.

I live where theres lots of ice, no hills, no curves so the tradeoff of poorer fuel economy due to heavier , and pricier to repair and maintain vehicles, has me with going with FWD and good studded winter tires.

If the guy wants AWD knowing it costs more, no problem. However I wouldn't say Subaru is the only vehicle to fit the bill by any stretch.

 

[JCH13]

There's no doubt that torque-vectoring systems like the ZF are a big advancement over a conventional AWD system. The control that the system exercises will help make the vehicle more predictable to the average driver. The "yaw movement" is basically controlled sliding, this keeps the vehicle pointing in the direction that the driver expects.

DSC systems exert a similar influence, but by using the brakes rather than the drive system.

It does not improve overall traction of the tires. It cannot make a car sustain more lateral acceleration or braking acceleration. It cannot defy physics.

It will probably help the average driver from doing something really stupid and will help keep the vehicle's behavior predictable to the average driver. It cannot sustain considerably higher cornering speeds nor reduce braking distance.

I am frequently seeing the word "performance" being used to describe aspects that are NOT performance in many of these articles. The mis-use of the term may be quite confusing to some.

 

[ND40oz]

I don't think anyone is claiming they defy physics (at least I hope not), what they do is allow the tires to better work with the traction they have available to them at that moment in time.

I had an 07 FJ full time awd with a torsen center diff, open diffs at the front and the back unless you locked the center diff and then you could lock the rear. I also had an 07 MDX at the same time, no locking capabilities but it did have SH-AWD. I can say from driving them both that the MDX was head and shoulders above the FJ in most winter conditions. The only time it wasn't was when there were a few feet of unpacked snow. With like tires, in most driving conditions the traction available to any given wheel varies depending on the surface it's on, whether that's dry pavement, wet pavement, slush covered pavement, snow packed pavement, icy pavement and everything in between. Since you're driving down the road, those conditions change constantly and a torque vectoring system can account for all of these things as it puts torque down to each individual wheel. With open diffs, you're just going to get wheel spin as torque goes to path of least resistance if one wheel has less traction then the other or if it has a traction control, it'll brake the spinning wheel to try and transfer torque but the system isn't actively transferring torque based on driver inputs and other sensors.

 

[exar333]

Snow tires are the best improvement, for sure, but AWD makes WORLDS of difference over RWD or AWD as well.

RWD in snow can be dangerous if you lose traction and the back starts to slip out to either side...

FWD vehicles can be very difficult to get out of heavy snow when you need to both steer and get enough tracton to 'get moving'

AWD gives a lot more confidence on slippery corners, assuming you have a good AWD system, because the car can shift power to the wheel that has the traction. This may only help you in 1/100 situations, but that difference does make you feel better on those white-knuckle drives across the state in a snowstorm.

JCH13 is spot-on with over-confidence though. You can't expect AWD cars to stop quicker or turn faster. It's easy to get a false sense of security because you can accellerate more quickly and driver faster, but that's just something you have to deal with.

 

[JCH13]

I don't think anyone is claiming they defy physics (at least I hope not), what they do is allow the tires to better work with the traction they have available to them at that moment in time.

I had an 07 FJ full time awd with a torsen center diff, open diffs at the front and the back unless you locked the center diff and then you could lock the rear. I also had an 07 MDX at the same time, no locking capabilities but it did have SH-AWD. I can say from driving them both that the MDX was head and shoulders above the FJ in most winter conditions. The only time it wasn't was when there were a few feet of unpacked snow. With like tires, in most driving conditions the traction available to any given wheel varies depending on the surface it's on, whether that's dry pavement, wet pavement, slush covered pavement, snow packed pavement, icy pavement and everything in between. Since you're driving down the road, those conditions change constantly and a torque vectoring system can account for all of these things as it puts torque down to each individual wheel. With open diffs, you're just going to get wheel spin as torque goes to path of least resistance if one wheel has less traction then the other or if it has a traction control, it'll brake the spinning wheel to try and transfer torque but the system isn't actively transferring torque based on driver inputs and other sensors.

All of your points are valid, and the advanced torque-vectoring certainly lets the car drive down the road more comfortably. Sometimes deceivingly comfortably. What it does NOT do is help with braking or steering, the two most important things to do in an emergency and the two things that actually keep a car on the road. AWD vehicles sometimes have worse braking/steering performance than their 2WD counterparts.

This is why AWD car drivers scare me (horrible generalization, but not at all uncommon) they think that because they can get up to speed more quickly than 2WD cars that they should actually drive faster than their 2WD counterparts, despite having comparable or inferior steering and braking. AWD helps you to get moving, that's it.

Frankly, I've never had an issue with 2WD vehicles in 11 years of driving in New England/NH. Neither has my entire family. The cars I have driven range from an open-diff RWD crown vic to a Volvo S80, to my Mazdaspeed3. None have ever failed to get me to a ski area on a snow day. I'm not arguing the AWD isn't nice to have in some situations, but it is far from necessary and only helps one ONE aspect of winter driving.

 

[ND40oz]

It does help steering, braking not at all unless you're also using engine braking at the same time and have something like ZFs system where it works on deceleration as well. SH-AWD is only good when you're applying power though. But it works great when applying power through a turn, you can feel it shift torque around, it's especially noticeable on slippery surfaces, something an open diff or just a brake based traction control system can't do.

 

[smackababy]

This is why AWD car drivers scare me (horrible generalization, but not at all uncommon) they think that because they can get up to speed more quickly than 2WD cars that they should actually drive faster than their 2WD counterparts, despite having comparable or inferior steering and braking. AWD helps you to get moving, that's it.

As someone who recently moved to an area with harsh winters and limited snow / ice driving experience, I can confirm this fear. I don't know how many times I've been passed by people doing 5-10MPH over the speed limit with snow on the road. Of course they are in an SUV or a xDrive BMW. The best part is once a little rain comes down, they all drive 15MPH under the speed limit.

 

[JCH13]

It does help steering, braking not at all unless you're also using engine braking at the same time and have something like ZFs system where it works on deceleration as well. SH-AWD is only good when you're applying power though. But it works great when applying power through a turn, you can feel it shift torque around, it's especially noticeable on slippery surfaces, something an open diff or just a brake based traction control system can't do.

I'm sure the SH-AWD system makes the car feel like it can turn better and helps the vehicle be more predictable in a turn, like I've said. However, putting any torque through the wheels takes away grip otherwise available for lateral acceleration (turning). This is a fact that no amount of torque vectoring can avoid. Tires have a fixed amount of total grip, and if that grip is all being devoted to steering/turning (on the threshold of sliding sideways) then the drive system is irrelevant because any torque on any wheel will cause a slide.

AWD engine braking CANNOT do better than ABS. A wheel does NOT have to be locked to be sliding, it just has to be spinning at a different speed than it should be.

I'll phrase my another way: very good AWD control systems allow drivers to ignorantly approach the limits of their car. The drivers are then totally surprised when they exceed their cars limits. A 2WD car has the same, or better, cornering and steering limits, provided the driver knows how to balance the car. BUT the 2WD car communicates that it is approaching its limits much sooner and more clearly.

 

[ND40oz]

It allows you to use the rear tires of the vehicle for cornering as well, not just your front two tires, by overdriving the outside rear tire, you generate that yaw movement that the ZF article refers to.

 

[Vic Vega]

I never had a problem with RWD sedans and I lived in Chicagoland half my life. I have a 4x4 Explorer that does very well.

No amount of AWD/4x4 magic will save you on ice.

 

[billybob-ssd]

So many people that don't know what the hell they are talking about. Subaru has symmetrical all wheel drive, and it is perhaps the best all wheel drive system you can get.

As for the unrelated theoretical high performance of four wheel drive, I go to the track. A lot. Nissan GT-R's are out there slaying Corvette Z06's and Porsche GT-3's all day long. The GT-R is a MUCH heavier car, but it murders the other sports cars because of that all wheel drive. It lets the car put all that horsepower to the pavement better than the other cars on the track.
I'm not talking about the drag race track, I am talking about a real race track like this one.
In fact, if you would like to come to the next HPDE event, I would be more than happy to watch a GT-R stomp any 2wd car you can bring.

 

[billybob-ssd]

It cannot make a car sustain more lateral acceleration....

But it DOES however increase the amount of acceleration possible under heavy lateral loads.

 

[XavierMace]

As for the unrelated theoretical high performance of four wheel drive, I go to the track. A lot. Nissan GT-R's are out there slaying Corvette Z06's and Porsche GT-3's all day long.

Unless that's in the snow, that has nothing to do with the topic at hand...

 

[JCH13]

It allows you to use the rear tires of the vehicle for cornering as well, not just your front two tires, by overdriving the outside rear tire, you generate that yaw movement that the ZF article refers to.

Like I said in an earlier post, it is a controlled slide. I can do the same thing in a RWD car with the gas, or a FWD car with the hand brake. That actually sacrifices grip.

So many people that don't know what the hell they are talking about. Subaru has symmetrical all wheel drive, and it is perhaps the best all wheel drive system you can get.

As for the unrelated theoretical high performance of four wheel drive, I go to the track. A lot. Nissan GT-R's are out there slaying Corvette Z06's and Porsche GT-3's all day long. The GT-R is a MUCH heavier car, but it murders the other sports cars because of that all wheel drive. It lets the car put all that horsepower to the pavement better than the other cars on the track.
I'm not talking about the drag race track, I am talking about a real race track like this one.
In fact, if you would like to come to the next HPDE event, I would be more than happy to watch a GT-R stomp any 2wd car you can bring.

No one is at all arguing that AWD cars wouldn't be fast around a track. AWD cars can do very well at the track because they are able to put power down sooner out of a corner as compared to most (all?) RWD and FWD cars. As I have mentioned before, AWD can instill a sense of over-confidence, which will reward risk-taking drivers at an HDPE.

However, you're comparing a $75k car, assuming it's a Z06 'vette (probably cheaper) to a $100k-$115k GTR. Not a very fair comparison. Also, at HDPEs there are many divers of varying skill levels and attitudes on the same track, making their car largely irrelevant. There was a forum member here who posted a picture of him driving a GTI passing an Audi R8. Do you think a GTI is faster than an R8?

Still though, stupid arguments and faulty comparisons aside, let's look at a real test with the only significant variable being the car itself.

Let's look at the same driver on the same track with multiple cars. Randy Pobst set the Mazda Raceway Leguna Seca lap record in, gasp, a Corvette ZR1, RWD. 2nd place is held by a Viper ACR, RWD. Next is a Z06 Corvette, I assume driven by Randy Pobst again, RWD. Then a McLaren MP4 12C, driven by Randy Pobst, RWD. Then a Devon GTX, RWD. Finally we have our fastest AWD car, an Aventator LP700, driven by Randy Pobst. Then a Porsche GT2 RS, RWD. Then a Ferrari 458 Italia driven by Randy Pobst, RWD. Then we get to the GTR in 9th place, driven by Randy Pobst.

Source: http://fastestlaps.com/tracks/laguna_seca.html
(I assume the #1 spot is a typo)

GTR in 3rd place behind two RWD cars: http://fastestlaps.com/tracks/willow_springs.html

Feel free to browse, I couldn't find a track where the GTR was beating ZR1 Corvettes or ACR Vipers. There are some tracks where it has a record, but there isn't much competition at those tracks.

I guess you're the one of those people who has no idea what the hell they are talking about.

 

[ND40oz]

Like I said in an earlier post, it is a controlled slide. I can do the same thing in a RWD car with the gas, or a FWD car with the hand brake. That actually sacrifices grip.

That's like saying an LSD on rwd car is creating a controlled slide when you're on the gas through a corner. You're transferring torque to the outer wheel with more grip, you're not sliding or losing traction at all, you're just using the extra traction on the outside wheel to help steer the vehicle.

 

[JCH13]

That's like saying an LSD on rwd car is creating a controlled slide when you're on the gas through a corner. You're transferring torque to the outer wheel with more grip, you're not sliding or losing traction at all, you're just using the extra traction on the outside wheel to help steer the vehicle.

Yes, that's exactly what I'm saying, assuming you're referring to 'throttle-on' oversteer.

Oversteer happens when the rear axle is sliding a little (or a lot). This slide can be quite controllable and advantageous, or it can be disastrous.

 

[FiLeZz]

http://www.youtube.com/watch?v=0_MXK2nzt2Y

http://www.youtube.com/watch?v=2OzK-oRPCbs




Long videos but worth a watch.

enjoy

 

[Vdubchaos]

Remember, Tires BEFORE the car.

Invest in a good set of tires for ANY vehicle you might have.

I will take FWD with Show tires over AWD with all seasons ANY day of the week and twice on Sundays.

 

[_Rick_]

I humbly submit this, for what AWD can do to turning grip.

https://www.youtube.com/watch?v=469mi4UOVK0

Torque vectoring allows you to counter yaw movements, that limit grip elsewhere, by countering them at the wheels, that still have sufficient grip.

This is irrelevant when braking, but evading obstacles stably becomes possible.

So what these enhanced ESPs do, is not increase maximum absolute grip, but they do increase realistically available grip, by controlling yaw and slip, before it destabilizes the car. Being able to break and accelerate each wheel independently, as is possible in a four wheel drive car, is what makes these systems really powerful. In a 2WD cars, there are always two wheels where you have limited control.

 

[ND40oz]

Yes, that's exactly what I'm saying, assuming you're referring to 'throttle-on' oversteer.

Oversteer happens when the rear axle is sliding a little (or a lot). This slide can be quite controllable and advantageous, or it can be disastrous.

Oversteer happens once you've exceeded the grip of the rear tires, the whole point in these systems is to use that grip up to the point where you haven't exceeded it. You don't need to have oversteer to use the rear of the vehicle to help bring it through a corner. What the system is doing is transferring more torque to the outside wheel to help bring the car around the corner, the inside rear wheel doesn't travel as fast when going around a corner and by shifting that additional torque to the outside wheel and overdriving it compared to the inside wheel, it helps bring the car around. This is all done without oversteer, you don't want to slide the rear of the car around, you want to use the outside wheel to help bring it around without exceeding the limits of your tires.