The Science of Driving

Quote: AZDuffman

SD?

Self defense. The Cooper Color Code developed by Colonel Jeff Cooper is very similar, only involving five steps instead of three. Same concept, though.

As long as we are talking snow driving, how about a pet peeve I have on it. Lets call this segment, "Knowing What 4WD is and is Not."

Back in the old days, lets call them the 1970s/80s, almost nobody had 4 wheel drive. There were some odd cars like the AMC Eagle, Subaru, and pick-up trucks with the feature but 90% of the cars on the road were not 4WD. Yet somehow we survived and got to where we were going. In the late 1980s, however, a segment of the population was convinced they "needed" 4WD.

Said people were almost afraid to venture out in the snow without it, and were afraid if they did they surely would end up in a ditch where they and their kids would not be found for weeks and might end up as the Donner Party did. That they rarely left populated suburbs did not matter. Might have to go to the drug store at the corner for milk after all. But does 4WD really help all that much?

First the obvious, if you are stuck, 4WD WILL help pull you out. If you have ever been stuck and see one wheel slipping and the other not moving you understand how if you could "lock" the wheels and the other three help you would be on your way. But wheels on cars are rarely "locked" for good reason. (Face, feel free to help add to this.)

In a straight line all the wheels are moving at the same RPM. But if you make a turn the inside wheels need to turn fewer RPM than the outside wheels. If they were at the same RPM one wheel would be slipping and the car would become very unstable very fast. With power going to all four wheels the same thing can happen. This is why most modern 4WD systems actually operate in 2WD in most conditions, along with lowering fuel consumption most cars just handle better under most conditions.

But we live in a nation where if it is on TV then it must be real. People see the 4WD in ads and figure it can do anything. They do not understand that 4WD is basically mostly useful just to get you going and has less utility the faster you go. It has ZERO utility to help you in a skid. And skids are where most winter accidents happen.

I still remember a day in WNY where it was not a heavy snow, but slippery enough that you had to give the road a lot of respect. I was in a small, FWD vehicle. I passed 5-10 vehicles in the ditch on the side of the road, every one of them some kind of SUV. Clearly the drivers felt that with 4WD they were invincible. With a buddy once and a salesman tried to say, "in South Buffalo there are lots of hills so you more need 4WD down there." Being from WPA where we have *real* hills I just shook my head.

One final thing, a good deal of why SUVs are "good in the snow" is ground clearance. Not having to use engine power to push snow moves the vehicle better.

Here are a few pieces of snow-driving wisdom I have picked up over the years:

1. You cannot learn how to drive in the snow without driving in the snow. Get to a big, empty, open parking lot and slide your car a bit. See how it handles. You steer the way the rear end is kicking out to get back to straight. This is opposite to most people's instinct.

2. Keeping a car moving is also an art form. You have to know just how to goose the gas to move but not spin the tires. You cannot practice this in a parking lot. My best advice is you have to modulate it, flooring it will get you nowhere, you need to learn to "rock" it.

3. The colder it gets the better you will do in the snow. Right near freezing out is the most dangerous time. Snow will melt and freeze at the same time. The air may be near 40 degrees but the road surface below 32. OTOH, if it is -10 then everything is frozen and snow actually lets you get grip. Do not take this to go flying down the highway, but do know how things act.

4. Watch for the unexpected. A buddy and I were leaving n Indian Casino and a car was going the wrong way down the interstate. Had I been in the left lane I would be at that great Casino and Sports Book in the sky. We still talk about it and it was one of the weirdest road experiences of my life.

5. It is always the other cars that affect you most. Leave work early or stay late.

Quote: Face

Self defense. The Cooper Color Code developed by Colonel Jeff Cooper is very similar, only involving five steps instead of three. Same concept, though.

Oh, got it. I think the chart I saw had more levels but I only remember the three and not worth researching it for a simple blog.

Quote: AZDuffman

(Face, feel free to help add to this.)

I shall, and thanks for participating. 4WD is definitely coming up, as is its impotent 4th cousin, AWD.

Quote: AZDuffman

1. You cannot learn how to drive in the snow without driving in the snow. Get to a big, empty, open parking lot and slide your car a bit. See how it handles. You steer the way the rear end is kicking out to get back to straight. This is opposite to most people's instinct.

100% agree. You cannot know this from just reading a book (or even my thread, as amazing as it is ;)). You have to go out and do it. Just be aware, there is a slight chance you might get approached by the 5-0 when doing it. As long as your age doesn't end in "-teen", you're not emulating Ken Block, and you're doing it well away from parked cars or on off hours, most 5-0 will understand with the worst being a warning that you can't do it anymore. Totally worth it considering the alternative, trying to learn it at speed in an emergency situation.

Quote: AZDuffman

2. Keeping a car moving is also an art form. You have to know just how to goose the gas to move but not spin the tires. You cannot practice this in a parking lot. My best advice is you have to modulate it, flooring it will get you nowhere, you need to learn to "rock" it.

"Modulating" is The Gauge. It's you finding and remaining as close to that 100% as you can. There's another nugget of wisdom that comes with sliding tires that I'm not sure where to put... I suppose I'll make an Advanced-Advanced section.

Quote: AZDuffman

3. The colder it gets the better you will do in the snow. Right near freezing out is the most dangerous time. Snow will melt and freeze at the same time. The air may be near 40 degrees but the road surface below 32. OTOH, if it is -10 then everything is frozen and snow actually lets you get grip. Do not take this to go flying down the highway, but do know how things act.

100% true, just as I posted in the weather section. The further away you get from liquid water on the temperature scale, the stickier things are. -10 powdered snow is like sand; slippery because it's loose, but is not slippery in and of itself.

Quote: Face

I shall, and thanks for participating. 4WD is definitely coming up, as is its impotent 4th cousin, AWD.

Will be interesting to hear as some AWD owners get upset if you say 4WD. When I did car loans I asked one guy if it was 2 or 4WD and he said "AWD." So I said, "4" and he kept repeating "AWD." I kind of didn't answer back.

Quote:

100% agree. You cannot know this from just reading a book (or even my thread, as amazing as it is ;)). You have to go out and do it. Just be aware, there is a slight chance you might get approached by the 5-0 when doing it. As long as your age doesn't end in "-teen", you're not emulating Ken Block, and you're doing it well away from parked cars or on off hours, most 5-0 will understand with the worst being a warning that you can't do it anymore. Totally worth it considering the alternative, trying to learn it at speed in an emergency situation.

I made the mistake of practicing in the HS parking lot. I kind of ended up doing a donut as I practiced and the VP saw me and flagged me down. He was upset but didn't write me up. He told the gym teacher who ran the lot and at the end of the day said gym teacher knocked on my window. After I rolled it down he grabs the back of my hair and says, "IF I CATCH YOU DOING DONUTS IN MY LOT AGAIN *YOU'VE HAD IT*!" As I was never in real trouble I got no "official" discipline, but back then there was "gym teacher justice" meaning whatever they did and you would wish they just gave you the detention slip. It worked out for all who understood it.

RWD is for manly men who can conquer the world and already have. OK, just kidding. But it is pretty bad ass, in my not so humble opinion. Of course, as with anything in life, it does have its drawbacks, which we will cover... now.

RWD is awesome because it separates accelerating from steering. Assuming you're not on the brakes, your fronts have all 100% available to steer you away from trees, dogs, oncoming cars, and joggers with earbuds in. The only way you can avoid stuff is to steer away from it; don't you want as much of that ability as possible? Only in a RWD do you get all 100% available for turning.

Another fantastic feature is the ability to use the throttle to turn. This has saved my soul times beyond count. Say you're approaching a turn, and whoops, you're coming in a little hot and your fronts start to slide. You get off the gas, which causes decelration and weight to shift forward. The extra weight allows your front tires to increase their maximum potential G. On top of that, the compression braking is acting on the rears, leaving them with less traction available than the fronts. With any luck, they will break free and start to slide. At this point, you can blip your throttle and really break the rear loose. That sharp input of acceleration leaves almost no traction left for keeping the rear straight. With any traction turning the front, it will overcome the tiny bit left in the rear and the rear will kick out, rotating the car and pointing it the way you want to go ie away from the ditch, tree, 10 kids waiting at the busstop. "But, Face" you may be saying "why do we want to slide?" Because it beats plunking a toddler, obviously! Once you get the vehicle pointed the way you want to go, it automatically tries to go that way. And, since your rears are under your control, you can use the throttle to increase or decrease the amount of side traction trying to straighten you out, preventing the "catch and hook" of FWD. Similar to FWD climbing a hill, you can modulate the throttle keeping the traction level at the desired amount, bringing the rear end back around slowly and under control.

Try it at home, it's fun as hell. Just drive in a snowy circle, maybe 50' wide at 10mph. Blip the throttle and get the rear out, and practice bringing it back in under control. You'll feel the "snap" when you do it wrong. You'll feel like a driving god when you do it right. In my truck on the back roads, I think absolutely nothing of taking corners at 60, knowing that it's going to break loose but absolutely confident I'll not only not crash, but I won't even lose speed and will keep the vehicle entirely within my own lane. For this, people think I'm foolish at best and a complete asshole at worst. But just last month, while negotiating a corner on the on-ramp of the I-190 in the rain, my truck broke loose at 70mph in door to door, bumper to bumper traffic. And I held that slide for 100', never leaving my lane or slowing a bit. I barely even got an adrenaline dump for it. Without being "that asshole", I would've been a statistic, just another 10 car pileup during the Buffalo rush hour.

RWD does have it's downsides. Unless you're driving a supercar with a six digit pricetag, most of the weight of your car is over the front tires. In a truck, with an open bed, even more so. That means the maximum potential G of the tires that drive is less than a FWD or 4WD. This is painfully apparent when climbing a snowy hill. If we took all the drive types and tested them on increasingly sloped hills, the RWD would give up first.

RWD is also the most wayward. In situations where traction is lost in a FWD, the front will gently drift to the right due to the crowned roads and the car remains mostly pointed in the direction you were headed. In a RWD, that drift is greatly accelerated, and said drift turns the entire car toward the oncoming lane. That makes people freak out, and when freaked out, people panic and do stupid things. Since most people think driving can be completely explained using two pedals, a wheel, and a hole to pour liquid in, RWD is usually avoided (even though it's way better)

Up next... 4WD (and the dispelling of all the damned myths)

I can't bring myself to devote an entire page to stupid AWD, so let's combine it with 4WD and start with how and why they're different.

As AZ so graciously offered, cars have what is called a differential which allows wheels to turn at different speeds. As he pointed out, without one, both tires would have to turn the same amount at all times. When you turn a corner, the inside corner needs to turn a lot less, and this would both cause the tire to skip and skid, as well as result in them resisting the turn and trying to go straight.

An AWD, while delivering power to all 4 wheels, does so through a differential both front and back. This is great for at-speed handling as well as tire wear, but it is absolute garbage in inclement weather situtations. As anyone who's ever been stuck, or anyone who's ever watched "My Cousin Vinny" knows, a differential can create that condition where one wheel is spinning in the muck and the other wheel doesn't move at all. That is the system an AWD vehicle is equipped with. Yeah, depending on a multitude of factors, the differential may at sometimes engage and give you quasi-4WD performance, but if those factors aren't met, you're just stuck. Simple as that.

A 4WD has a locking differential that forces both front wheels to turn always. If you have a 4WD, try it at home. Get on dry pavement, engage the 4WD, then turn as tight as you can. Hard to turn, isn't it? You can hear the tires skidding, can't you? That is the difference between AWD and 4WD.

So, back to the pros and cons. 4WD, as AZ had already said, is all about going forward. Whether FWD or RWD, you only have two tires worth of traction with which to accelerate. If those tires don't possess the friction to push or pull you through the snow or mud, then you, sir, are stuck. 4WD gives you two more tires worth of traction to push or pull you through the junk.

But that, my friends, is IT

Think of what we now know about friction and The Gauge. Think of how we now know how tires work, how there's only 100% available, and all the stuff we've gone over. Now ask yourself "how would adding acceleration forces, which would use some of the 100%, allow me to turn better?"

Quite obviously, it does not. It CAN not. You can't take away something and at the same time have more of that same something. And this is why AZ and all the rest of us see so many SUVs in the ditch. People hit their 4WD, can accelerate faster than normal and think they're glued to the road, never realizing they now have less turning traction available until they need it and it's not there. To recap, 4WD gives you two more tires worth of accelration traction. The only way to get two more tires worth of turning traction... is to add two more tires that turn ;)

For this reason, my truck almost never goes into 4WD. The only time it does is when I have to stop and then restart on that hill mentioned earlier due to a stuck FWD car, or when passing in the snow. As you can see, both of these situations call for increased acceleration traction. Once either of those situations have been completed, I'm back in RWD mode so I keep all 100% of the fronts available for turning. Completing your entire commute in 4WD not only wastes gas, but slightly decreases the traction available in the fronts same as a FWD.

If anyone ever tells you they keep it in 4WD for handling purposes, tell them you need to pee, get them to stop, get out, and walk home. You're likely to be walking home later anyways =p

Up next... Advance Advanced Random Stuff.

Quote: Face

RWD is also the most wayward. In situations where traction is lost in a FWD, the front will gently drift to the right due to the crowned roads and the car remains mostly pointed in the direction you were headed. In a RWD, that drift is greatly accelerated, and said drift turns the entire car toward the oncoming lane. That makes people freak out, and when freaked out, people panic and do stupid things. Since most people think driving can be completely explained using two pedals, a wheel, and a hole to pour liquid in, RWD is usually avoided (even though it's way better)

I wondered why they drifted to the right. FWIW I prefer FWD for most driving because you can steer and pull the car at the same time whereas in snow a RWD can be like pushing a chain.

Quote: Face

An AWD, while delivering power to all 4 wheels, does so through a differential both front and back. This is great for at-speed handling as well as tire wear, but it is absolute garbage in inclement weather situtations. As anyone who's ever been stuck, or anyone who's ever watched "My Cousin Vinny" knows, a differential can create that condition where one wheel is spinning in the muck and the other wheel doesn't move at all. That is the system an AWD vehicle is equipped with. Yeah, depending on a multitude of factors, the differential may at sometimes engage and give you quasi-4WD performance, but if those factors aren't met, you're just stuck. Simple as that.

A 4WD has a locking differential that forces both front wheels to turn always. If you have a 4WD, try it at home. Get on dry pavement, engage the 4WD, then turn as tight as you can. Hard to turn, isn't it? You can hear the tires skidding, can't you? That is the difference between AWD and 4WD.

Thanks for explaining it this way. I didn't realize how useless AWD was. FWIW I have already tried the 4WD on dry pavement at the boat ramp where I put it in 4WD so it locks before I back into the water. Knew it caused this but wasn't so sure why.

Quote: AZDuffman

I wondered why they drifted to the right. FWIW I prefer FWD for most driving because you can steer and pull the car at the same time whereas in snow a RWD can be like pushing a chain.

I'm so glad you've experienced it, because you now understand perfectly. It's a weird phenemenon. No one think that just sitting at a red light requires friction. Without it, you'd still slide right off the road just from the crown in the road. Spinning the tires beautifully illustrates the points I've been making. You're using all 100% to go forward, there's nothing left preventing it from going sideways. With nothing left, it slides to the right, the direction the road is crowned =)

And my FWD hatred is mostly jest. I mean, I do hate them, but obviously an economical car just can't be RWD, especially not in our parts. Even my truck, were it only RWD, would not get me to Salamanca. Then I'd have to work in the Falls everyday, and who wants that?

Maybe back when a family sedan came in at 4,500lbs... but I can't imagine Mosca tooling around our parts in February in his Miata XD

Quote: AZDuffman

Thanks for explaining it this way. I didn't realize how useless AWD was. FWIW I have already tried the 4WD on dry pavement at the boat ramp where I put it in 4WD so it locks before I back into the water. Knew it caused this but wasn't so sure why.

You're quite welcome. There was a time when I thought AWD was just some moniker to gain attention, but was the same as 4WD. Very wrong, and knowing why is helpful when I get stuck with one. A little knowledge is a good thing, glad to pass some along =)