5 ms·

The mistake most people with AWD make can be summed up in one of my favorite phrases: even two wheel drive has four wheel braking. Winter driving is all about g

The mistake most people with AWD make can be summed up in one of my favorite phrases: even two wheel drive has four wheel braking. Winter driving is all about grip, having the extra drive wheels does nothing to help your tires maintain mechanical grip on the road.

swagmoney69 6y ago
Driving in general is all about grip. Hell, in every form of racing I would argue tires are first and foremost the most important part of a car.
emilecantin 6y ago
Yeah, that's exactly how I put it as well. Winter tires, once you've seen / touched them, are visibly different: different tread, way softer rubber, etc. I also pretty much always use studded tires, as we've been getting a lot of freezing rain in the last few years, and the one accident I've ever had was due to that (fell in the ditch while driving at ~30 km/h. I had a hard time _walking_ on the road without slipping). The flip side is that they're more likely to skid on pavement, especially in summer. That's why you have both.
- snuxoll 6y ago
  > Winter tires, once you've seen / touched them, are visibly different: different tread, way softer rubber, etc. Exactly, tires are the single most important element of winter driving. If you live in a place with mild winters all season tires can get you far, but if you get a lot of snow or ice seasonal tires are critical. Cold tires are slick tires that will slide all over hell and back, the tread on winter tires is designed to better move slush and snow out of the way so the contact patch can hopefully reach the road surface; while the softer rubber heats easier so it can get to a nice 'grippy' temperature and grab hold of the road even in conditions where the wet and cold are trying to sap heat from it. During the warmer months these winter tires will be less effective because they have smaller contact patches (due to more/deeper grooves in the tread to drive moisture away), and will actually get hotter than desired (softer rubber) causing a loss of grip as the rubber will want to start shearing off instead. Everyone needs to remember no matter what fancy engine, electronics, etc. your car has - your tires are the only thing that actually touches the ground. Acceleration, braking and turning are all highly depending on their ability to grip the ground (and withstand the forces being placed on them) - so make sure you have the right ones and don't put off replacing ones that are nearing the end of their life.
majormunky 6y ago
I think the AWD helps a lot more with starting out. My old FWD car (no snow tires) would not be able to stop at a stop light that was on an incline and then start again without spinning the tires forever. The same thing with my Subaru (AT tires) and there’s no slip at all.
- jeffbee 6y ago
  FWD cars can't start on an incline in the rain, either. It's just a fundamental problem of that architecture. Electronic traction control can help somewhat.
- grecy 6y ago
  Absolutely correct, though how many accidents occur because a vehicle can't get going? (hint: none) In winter situations, it's stopping (and steering) you need to worry about, not going. (Said as someone who drives a BIG 4x4 with excellent winter tires in a part of Canada where they are required by law)
  - sliken 6y ago
    None? Seen plenty of FWD stuck at the bottom of a hill that an AWD can climb. As you might imagine hanging out at the bottom of a hill is a great way to get hit.
    - grecy 6y ago
      The only crashes were stationary vehicles get hit are because the vehicle that hits them can't stop.
      - sliken 6y ago
        Right. Just what you get when it's hilly, slippery, and you have a bunch of FWD that can't climb.
- throwaway0a5e 6y ago
  It helps a ton any time you have to touch slush. Which is often. People aren't stupid. There's a reason why everyone who can swing it buys an AWD to commute and not everyone buys snow tires. The snow tire is still gonna be slush-o-planing any time you go onto highway slush of appreciable depth. Heck a mud tire with big fat grooves is your best bet when the tire is on that. There is no tire (suitable for general use, I'm sure the Florida mud racing crowd has something up their sleeve) that can handle that without planing. There just isn't enough space between the tread blocks for all that viscous fluid to be forced through (assuming you're going like 20+mph) and you end up on top of it. Being able to change lanes and enter traffic from side streets/driveways with less slip is just a soooooo much better experience than not being able to do those things gracefully but in exchange for a slightly a better worst case stopping distance in fairly rare conditions (ice and fresh powder). Commuting in snow is nothing like those commercials where they drive on ice. All the traction in the world won't help you when your problem is that the tire isn't making contact with the road. Driving on ice and fresh powder are so rare it's no surprise that consumers don't optimize for that. Sure you can put snow tires on your AWD but the lions share of improvement in the conditions people actually encounter comes from AWD.
mmmBacon 6y ago
I suppose that’s good advice because many people overdrive their vehicle’s AWD in winter but it’s not explicitly correct. Real life as usual is more complicated. Braking in AWD scenario and traction are not same as your example and depends on the power split between the front and rear and how the 2 are coupled together. In 4WD with the 50/50 split, the drive shafts are locked together through the differential and braking is much more effective in part due to the fact that the braking is more evenly distributed among the 4 wheels since the drive shafts are locked. Also when you lock up the brakes in 4WD usually 2 wheels on the diagonal keep turning, again due to how the differentials work. This is not the case in FWD.
- emilecantin 6y ago
  > braking is more evenly distributed among the 4 wheels since the drive shafts are locked. There is something seriously wrong about either my understanding of how cars work, or yours. I have brake disks and brake pads on all 4 wheels of my (FWD) car; pretty much every car does. How would a drive-shaft help "distribute" braking power? The limiting factor here isn't the force each brake can exert on their wheel (they're pretty much always able to lock up), it's the traction between the wheel and the ground (the tire). In my mind, an "ideal" emergency braking scenario would be all 4 wheels braking at the maximum force they can without slipping, and that can be done much better by the ABS system when they're all disconnected from each other. A driveshaft connecting them would be irrelevant at best, but more likely it's a nuisance.
  - sliken 6y ago
    4wd/awd is pretty complicated. Some depend mostly on hardware (like subaru), others try to use sensors and torque control and/or brake control to put the torque where it's needed. AWD is complicated with 3 differentials that can be a mix of open, limited slip, or actively controlled (by torque split or brake based system). It's especially tricky since it's not the actual traction that matters as much as the driver perceived traction and predictability. I've drivin AWD systems with snow tires that seemed to have more traction than my subaru with all seasons, but ended up driving more slowly because I couldn't predict what it was going to do. Subaru seems to communicate well with the driver, and making sliding just not a big deal. Other cars make it harder to tell what a given throttle/braking input is going to result in and can trigger heavy front or rear bias based on what the sensors/software tell it to do. It drives me nuts when a car acts completely differently in high traction and low traction conditions, especially when it changes one second to the next. Some Subaru folks make fun of other systems that they call "slip and grip", where there's a heavy FWD bias (minimal torque to the rear), until AFTER you start slipping. My WRX had a limited slip in the rear, center diff was a viscous coupling (100% mechanical/no software), and a open front diff. It was reassuring, never surprised me, and even when significant slipping I could always put the car exactly where I wanted. Even when crab crawling sideways in a parking lot at 2 mph it never surprised me. Numerous Toyota, Ford, Honda, and BMW cars I tried would try to outsmart me. Limiting throttle, moving the torque around, limiting braking forces, etc. Last thing I want when climbing a hill is the car to cut the throttle because one of 4 wheels slipped for 50ms. Consumer reports tested a Subaru forester, Toyota RAV 4, and Honda CRV in heavy snow conditions and concluded the Subaru was a clear winner despite them all having similar dry road performance and AWD. I think for normal snowy roads Subaru does it best with a mostly manual system, the ABS and traction control has a light touch that can be mostly avoided. But for heavy offroad the best thing to do (in certain messy conditions) is lock all differentials, which is something the Subaru can't do.
ip26 6y ago
More simply: Ok, your car has four wheel go. But EVERY car already has four wheel stop.
sliken 6y ago
I find that a very weird statement. Driving a FWD, especially when climbing, shows how limited the grip of FWD is. AWD distributes the power to twice as many wheels (often 3 times actually) and loses grip less often. Sure both cars would descend the same, but you can always lower your speed to decrease the amount of traction you need. When climbing there's no such options for FWD.
- snuxoll 6y ago
  My Prius can climb a hill like a champ, until the battery is drained and the poor ICE is all that's turning the driveshaft. Torque matters when it comes to hills, not the number of wheels connected to a driveshaft.
  - sliken 6y ago
    Well this discussion is about snow/slippery conditions, engine torque is largely irrelevant.
    - snuxoll 6y ago
      Torque is highly relevant, the entire 'benefit' of AWD is being able to distribute torque to all four wheels instead of two. Thing is, with winter tires even a Prius has enough mechanical grip to put the extra torque from the MG's down and many AWD vehicles won't be able to max theirs out with all season tires. When it comes to winter driving the entire perceived benefit of AWD vehicles for commuter use goes out the window as soon as you need seasonal tires, basically. Yes, it will still better help put the power down given equal tires - but at that point the extra cost of the AWD system isn't giving you too much benefit if you are only buying it for winter driving.
      - sliken 6y ago
        Yes, the distribution of torque is very important and is the reason for AWD. But the amount of torque is not. When it's treacherous out even 5% of a normal cars HP/Torque is plenty. I've heard the FWD + snow tires beats AWD + all seasons before and personally I don't believe it, but it's a pretty subjective thing. The big win for AWD is predictability and control, not that I want to go around corners sideways at 100 mph rally style. Having control over the car, even when sliding, without any rear or front bias just makes for a MUCH more controllable car. My Subaru forester with AWD and all seasons handled numerous treacherous conditions, sometimes so bad that every highway around me was closed. I used to do 6 7200 foot passes every weekend, often in the middle of storms dropping 2-3 feet. My main problem on the roads was others that don't know how to drive and block the roads. I've driven roads so slick that going too slow would cause you to slide off the road. I'd have to apply torque, while sliding, to keep the 10-15 mph required to avoid sliding to the inside of every banked turn. Which would be MUCH harder with FWD or RWD. Amusingly at chain control points, often the workers would look back in the line, see my Subaru and pull me out of line and let me go through with a smile and a wave. Presumably because there are (or weren't anyways) any non-AWD Subarus (this was before the BRX) and Subarus aren't the typical cars getting stuck and causing problems. Sure AWD and snow tires is even better, just seems overkill for the highways in the high sierras.

swagmoney69 6y ago

Driving in general is all about grip. Hell, in every form of racing I would argue tires are first and foremost the most important part of a car.

emilecantin 6y ago

Yeah, that's exactly how I put it as well. Winter tires, once you've seen / touched them, are visibly different: different tread, way softer rubber, etc. I also pretty much always use studded tires, as we've been getting a lot of freezing rain in the last few years, and the one accident I've ever had was due to that (fell in the ditch while driving at ~30 km/h. I had a hard time _walking_ on the road without slipping). The flip side is that they're more likely to skid on pavement, especially in summer. That's why you have both.

snuxoll 6y ago
> Winter tires, once you've seen / touched them, are visibly different: different tread, way softer rubber, etc. Exactly, tires are the single most important element of winter driving. If you live in a place with mild winters all season tires can get you far, but if you get a lot of snow or ice seasonal tires are critical. Cold tires are slick tires that will slide all over hell and back, the tread on winter tires is designed to better move slush and snow out of the way so the contact patch can hopefully reach the road surface; while the softer rubber heats easier so it can get to a nice 'grippy' temperature and grab hold of the road even in conditions where the wet and cold are trying to sap heat from it. During the warmer months these winter tires will be less effective because they have smaller contact patches (due to more/deeper grooves in the tread to drive moisture away), and will actually get hotter than desired (softer rubber) causing a loss of grip as the rubber will want to start shearing off instead. Everyone needs to remember no matter what fancy engine, electronics, etc. your car has - your tires are the only thing that actually touches the ground. Acceleration, braking and turning are all highly depending on their ability to grip the ground (and withstand the forces being placed on them) - so make sure you have the right ones and don't put off replacing ones that are nearing the end of their life.

majormunky 6y ago

I think the AWD helps a lot more with starting out. My old FWD car (no snow tires) would not be able to stop at a stop light that was on an incline and then start again without spinning the tires forever. The same thing with my Subaru (AT tires) and there’s no slip at all.

jeffbee 6y ago
FWD cars can't start on an incline in the rain, either. It's just a fundamental problem of that architecture. Electronic traction control can help somewhat.
grecy 6y ago
Absolutely correct, though how many accidents occur because a vehicle can't get going? (hint: none) In winter situations, it's stopping (and steering) you need to worry about, not going. (Said as someone who drives a BIG 4x4 with excellent winter tires in a part of Canada where they are required by law)
- sliken 6y ago
  None? Seen plenty of FWD stuck at the bottom of a hill that an AWD can climb. As you might imagine hanging out at the bottom of a hill is a great way to get hit.
  - grecy 6y ago
    The only crashes were stationary vehicles get hit are because the vehicle that hits them can't stop.
    - sliken 6y ago
      Right. Just what you get when it's hilly, slippery, and you have a bunch of FWD that can't climb.
throwaway0a5e 6y ago
It helps a ton any time you have to touch slush. Which is often. People aren't stupid. There's a reason why everyone who can swing it buys an AWD to commute and not everyone buys snow tires. The snow tire is still gonna be slush-o-planing any time you go onto highway slush of appreciable depth. Heck a mud tire with big fat grooves is your best bet when the tire is on that. There is no tire (suitable for general use, I'm sure the Florida mud racing crowd has something up their sleeve) that can handle that without planing. There just isn't enough space between the tread blocks for all that viscous fluid to be forced through (assuming you're going like 20+mph) and you end up on top of it. Being able to change lanes and enter traffic from side streets/driveways with less slip is just a soooooo much better experience than not being able to do those things gracefully but in exchange for a slightly a better worst case stopping distance in fairly rare conditions (ice and fresh powder). Commuting in snow is nothing like those commercials where they drive on ice. All the traction in the world won't help you when your problem is that the tire isn't making contact with the road. Driving on ice and fresh powder are so rare it's no surprise that consumers don't optimize for that. Sure you can put snow tires on your AWD but the lions share of improvement in the conditions people actually encounter comes from AWD.

mmmBacon 6y ago

I suppose that’s good advice because many people overdrive their vehicle’s AWD in winter but it’s not explicitly correct. Real life as usual is more complicated. Braking in AWD scenario and traction are not same as your example and depends on the power split between the front and rear and how the 2 are coupled together. In 4WD with the 50/50 split, the drive shafts are locked together through the differential and braking is much more effective in part due to the fact that the braking is more evenly distributed among the 4 wheels since the drive shafts are locked. Also when you lock up the brakes in 4WD usually 2 wheels on the diagonal keep turning, again due to how the differentials work. This is not the case in FWD.

emilecantin 6y ago
> braking is more evenly distributed among the 4 wheels since the drive shafts are locked. There is something seriously wrong about either my understanding of how cars work, or yours. I have brake disks and brake pads on all 4 wheels of my (FWD) car; pretty much every car does. How would a drive-shaft help "distribute" braking power? The limiting factor here isn't the force each brake can exert on their wheel (they're pretty much always able to lock up), it's the traction between the wheel and the ground (the tire). In my mind, an "ideal" emergency braking scenario would be all 4 wheels braking at the maximum force they can without slipping, and that can be done much better by the ABS system when they're all disconnected from each other. A driveshaft connecting them would be irrelevant at best, but more likely it's a nuisance.
- sliken 6y ago
  4wd/awd is pretty complicated. Some depend mostly on hardware (like subaru), others try to use sensors and torque control and/or brake control to put the torque where it's needed. AWD is complicated with 3 differentials that can be a mix of open, limited slip, or actively controlled (by torque split or brake based system). It's especially tricky since it's not the actual traction that matters as much as the driver perceived traction and predictability. I've drivin AWD systems with snow tires that seemed to have more traction than my subaru with all seasons, but ended up driving more slowly because I couldn't predict what it was going to do. Subaru seems to communicate well with the driver, and making sliding just not a big deal. Other cars make it harder to tell what a given throttle/braking input is going to result in and can trigger heavy front or rear bias based on what the sensors/software tell it to do. It drives me nuts when a car acts completely differently in high traction and low traction conditions, especially when it changes one second to the next. Some Subaru folks make fun of other systems that they call "slip and grip", where there's a heavy FWD bias (minimal torque to the rear), until AFTER you start slipping. My WRX had a limited slip in the rear, center diff was a viscous coupling (100% mechanical/no software), and a open front diff. It was reassuring, never surprised me, and even when significant slipping I could always put the car exactly where I wanted. Even when crab crawling sideways in a parking lot at 2 mph it never surprised me. Numerous Toyota, Ford, Honda, and BMW cars I tried would try to outsmart me. Limiting throttle, moving the torque around, limiting braking forces, etc. Last thing I want when climbing a hill is the car to cut the throttle because one of 4 wheels slipped for 50ms. Consumer reports tested a Subaru forester, Toyota RAV 4, and Honda CRV in heavy snow conditions and concluded the Subaru was a clear winner despite them all having similar dry road performance and AWD. I think for normal snowy roads Subaru does it best with a mostly manual system, the ABS and traction control has a light touch that can be mostly avoided. But for heavy offroad the best thing to do (in certain messy conditions) is lock all differentials, which is something the Subaru can't do.

ip26 6y ago

More simply: Ok, your car has four wheel go. But EVERY car already has four wheel stop.

sliken 6y ago

I find that a very weird statement. Driving a FWD, especially when climbing, shows how limited the grip of FWD is. AWD distributes the power to twice as many wheels (often 3 times actually) and loses grip less often. Sure both cars would descend the same, but you can always lower your speed to decrease the amount of traction you need. When climbing there's no such options for FWD.

snuxoll 6y ago
My Prius can climb a hill like a champ, until the battery is drained and the poor ICE is all that's turning the driveshaft. Torque matters when it comes to hills, not the number of wheels connected to a driveshaft.
- sliken 6y ago
  Well this discussion is about snow/slippery conditions, engine torque is largely irrelevant.
  - snuxoll 6y ago
    Torque is highly relevant, the entire 'benefit' of AWD is being able to distribute torque to all four wheels instead of two. Thing is, with winter tires even a Prius has enough mechanical grip to put the extra torque from the MG's down and many AWD vehicles won't be able to max theirs out with all season tires. When it comes to winter driving the entire perceived benefit of AWD vehicles for commuter use goes out the window as soon as you need seasonal tires, basically. Yes, it will still better help put the power down given equal tires - but at that point the extra cost of the AWD system isn't giving you too much benefit if you are only buying it for winter driving.
    - sliken 6y ago
      Yes, the distribution of torque is very important and is the reason for AWD. But the amount of torque is not. When it's treacherous out even 5% of a normal cars HP/Torque is plenty. I've heard the FWD + snow tires beats AWD + all seasons before and personally I don't believe it, but it's a pretty subjective thing. The big win for AWD is predictability and control, not that I want to go around corners sideways at 100 mph rally style. Having control over the car, even when sliding, without any rear or front bias just makes for a MUCH more controllable car. My Subaru forester with AWD and all seasons handled numerous treacherous conditions, sometimes so bad that every highway around me was closed. I used to do 6 7200 foot passes every weekend, often in the middle of storms dropping 2-3 feet. My main problem on the roads was others that don't know how to drive and block the roads. I've driven roads so slick that going too slow would cause you to slide off the road. I'd have to apply torque, while sliding, to keep the 10-15 mph required to avoid sliding to the inside of every banked turn. Which would be MUCH harder with FWD or RWD. Amusingly at chain control points, often the workers would look back in the line, see my Subaru and pull me out of line and let me go through with a smile and a wave. Presumably because there are (or weren't anyways) any non-AWD Subarus (this was before the BRX) and Subarus aren't the typical cars getting stuck and causing problems. Sure AWD and snow tires is even better, just seems overkill for the highways in the high sierras.