The Science of Driving

Quote: Face

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

I used to hate them because they are all against the classic US car layout but over the years my daily care has become as much an appliance as my TV and to put money into anything to fancy it up I now see as something I outgrew. Where I once saw a cool ride I now see a waste of money. I would like a nice convertible for summer but that is all. Since I had FWD in the snow I never looked back. My next car will be a small SUV so may go 4WD or may not, want something I can tow small trailer with and room to haul some small stuff. Been using my Accent as a pick-up truck doing this house and see some value to utility as the mileage will be about what the Accent gets.

Quote:

There was a time when I thought AWD was just some moniker to gain attention, but was the same as 4WD.

It is a moniker to gain attention.

Totally agree on the nice car issue. To think of all the money I wasted on accoutrement in my youth. Up in our parts, it’s a total waste. As someone who has but one car that must be put through NY winters every year, having a car for 5-10 years is the limit. I might like loud pipes and big tires and a keen paint job on my pick ‘em up, but all that will be trashed before they’re even paid off. I can’t be bothered anymore.

The only way it makes sense is if you have a true cruiser. Something you take out for pleasure between May and October, and don’t have to drive in the rain and the snow. Maybe someday…

Quote: Face

Totally agree on the nice car issue. To think of all the money I wasted on accoutrement in my youth. Up in our parts, it’s a total waste. As someone who has but one car that must be put through NY winters every year, having a car for 5-10 years is the limit. I might like loud pipes and big tires and a keen paint job on my pick ‘em up, but all that will be trashed before they’re even paid off. I can’t be bothered anymore.

The only way it makes sense is if you have a true cruiser. Something you take out for pleasure between May and October, and don’t have to drive in the rain and the snow. Maybe someday…

I used to do some of it but it was on fancy cars not street-racers. I still remember a buddy got a Dodge Demon in high school. Slick tires, mag wheels, the lot; all in High School. By 18 months out of school it had all the signs of someone who could not afford it. The mag wheels on the front were then regular tires from a junker he owned. Plenty of bodywork showing. Well, you can guess the rest. Actually you would be amazed at what happened next. If there is interest I can post the story which is a good story of how to waste a lot of money and I mean a LOT. As another side note, to show how marketing affects people he and some other buddies seemed to think the Dodge Demon was somehow different than the Plymouth Duster. I mean they thought one was just way better than the other.

Today I merely laugh at people with wheels and tires that are 25% or more of the KBB value yet are so living the rest of life on the edge.

Quote: AZDuffman

If there is interest I can post the story which is a good story of how to waste a lot of money and I mean a LOT.

Go for it. I'd surely share my own, as I have no shortage of asshats to laugh at who do similar stuff ;)

Now for the Advanced-Advanced stuff. We’re now getting more into stuff that happens on-the-edge, where most people avoid going. However, I hope some part of this might sink in and assist in your daily commute, or help when you accidently find yourself on the edge.

Tires – Like many things, I have studied tires more than anyone who is not getting paid for it should. Brush models, theoretical models, rubber composition and traits… the list goes on. Much of what I’ve learned I’ve already shared, but there’s an added little queerness to them that I think everyone should know.

You know that tires, whatever traction level they are capable of, can only achieve 100% of that capability. We know that what that 100% represents changes based on a myriad of factors, and we know what those factors are. We know what amount of that 100% we use is based on our actions, and we know how our actions affect it. What is not widely known is that when we go over that 100%, everything changes.

For reasons that I am unable to comprehend and therefore cannot convey, a sliding tire is only capable of exerting 70% - 80% of its maximum traction. You heard right. If a tire is capable of 1G, you will near pulling 1G of lateral force the faster you go and the harder you turn. But once that tire starts sliding, that tire is now only capable of holding .7-.8 G.

This is important to know for two reasons. Firstly, if you’re nearing the limit in a corner, you can’t expect a slide to be something that’s easily ceased. It’s not like you can just peek above that 100% and then bring it right down to 99% again and be fine. Once a slide is engaged, you have to lower the amount of traction you’re asking from your tires by 30% for them to regain control. Second, this is what enhances that “catch” in a slide so badly. Once you go over 100% and start sliding, you need to bring it back down to 70% for it to catch. And when it catches, it catches at 70% and then immediately shoots to whatever your inputs are asking from it. Since most people are completely off all inputs when trying to correct a slide, what they’re asking for is it all. So that 70% the tires are exerting to make the car return to a straight orientation instantly shoots to 90%-95%-100% and the car violently snaps back toward straight.

And that last part, friends, is what I mean by steering with throttle and why I so love RWD. When I slide and my rears fight to regain going straight, I can modulate the throttle and use some of that traction for forward movement, lessening the amount being used for straightening movement. As a result, my slides recover with such pillow soft gentleness that I won’t even spill your coffee ;D Try it at home. Seriously. A little work in a snow covered lot could save you a walk home, a hefty repair bill, or even your life.

Another hinky thing to watch for comes when using RWD. We briefly covered a differential and what it does, although you will not find a deeper explanation on one here. I feel the same grinding in my brain when trying to understand a differential as I do when trying to solve Wiz’s math problems on WoV; it just doesn’t compute. But what we do know is it creates a difference in the forces between the wheels on each side of the car. In a RWD car, the right wheel is the primary drive wheel. When you hit the gas, it is this wheel that’s doing all the work while the left one just rolls. Everyone knows the one-wheeler-peeler, right? You hammer the gas, peel out, and you get one sad line of black. That’s your differential at work. Under almost all circumstances, that right tire will be the only one that ever makes you go forward.

Since it is the right tire that drives and your left just rolls, this causes a difference in available friction. Imagine we’re in an open, snow covered lot. We’re going 10mph, and we begin to turn to the right while accelerating. What will happen is the weight of the vehicle will shift to the left, thanks to inertia/centrifugal force. That left tire now has increased maximum traction available thanks to the extra weight acting on it, and since it doesn’t “drive”, it is using all 100% of that to hold the road in the turn. The right, on the other hand, has lessened maximum traction thanks to the weight leaving it. It is also being asked to hold the road as well as accelerate, so it’s likely to go over 100% and spin in a one-wheeler-peeler. But, since the left has a good grip, you still make the turn. Now we do the same thing, but turn to the left. All the weight now shifts to the right, lightening the load of that left tire. It now has reduced maximum available traction and is much more likely to break free. Additionally, the right tire, which while having additional weight to increase its maximum potential traction, is also being asked to drive. The turning plus the driving is likely to put the right tire over 100%, and the left is barely hanging on since you’ve reduced its traction by getting the weight off it. As a result, the same turn taken at the same speed and the same intensity of cornering is much more likely to lose control turning to the left as opposed to turning to the right. Again, try it at home.

These same concepts can be used for all drives of cars. RWD, FWD, AWD and 4WD, the concepts never change. The only thing that changes is where your drive inputs go, and how those input affect the individual tire. If you can picture this in your mind, picture how your inputs affect each tire, see the weight shifting on and off tires as you turn, and see The Gauge moving in kind, I’m telling you, you will never lose control and crash again.

That is pretty much everything I have, with one exception. I think I will make one more post in an attempt to rid the world of ABS. Perhaps, after reading, you too will pull your ABS fuse to disable it on your own car as I have. I'll give that a whack as soon as I find a free moment. Soo...

Up next - ABS and why it'll kill you.

OK, so here it is. First, I'm not going to let my agenda allow me to fill this thread with misinformation, so I will start with a full admission - ABS under normal driving conditions is superior and safer in every way.

ABS works by electronics taking over your brakes and pumping them at hummingbird-wing speeds. This allows the vehicle to exert maximum braking force without locking up the wheels. Since we've determined that a sliding tire can only produce 70% of its maximum traction, it's clear to see why ABS is superior. You could line me up in identical cars and take 100 runs each in ABS and normal brakes, and if I ever out brake ABS with my manual foot, I'll admit, it'd be purely by luck.

Also, since ABS prevents a lock up, it'll allow you to steer while in an emergency braking scenario. As we've also learned, a locked wheel which is using 100% of its traction to stop has nothing left over to turn. ABS, since it prevents the wheel from locking, will give you something left over to turn and allow you to steer even if in a full out panic stop.

There. I said it. And it pains me ;)

What ABS prevents, and why I refuse to use it, is emergency slide recovery. To understand this, we need to understand some terms I will borrow (and probably butcher) from aviation.

The first is vector (feel free to use your own term if I got this wrong). This is the direction we're heading. It doesn't matter if we're facing it, pointed at it, or if we're skidding upside down on our roof and can't see it. It's not the way we want to go, it's the way we are going.

The second is heading. Heading is the way we are pointed, the way we want to go.

Now, in almost all cases, the heading and vector match. When your car is under control, they always do. You point the car, it goes in that direction. Simple, right?

It's when they don't that people freak out. When the heading and vector don't match, you are in a slide. The problem almost all people have is that they put the priority on heading and don't think twice about vector.

This. Is. Wrong! The way you're facing in a slide is information. It'll tell you what went wrong and what you need to do to correct. Under no circumstances can a heading hurt you. It doesn't matter if you're on a tilt-a-whirl spinning round and round. If you're spinning round and round but doing so in your lane with no one around you, what happens? Nothing!

Vector, on the other hand, will kill you. If your vector has you headed right for a tree at 70, but your heading has you facing right down the middle of your lane where you want to go, are you safe? No. You're about 1.5 seconds away from serious injury or death. Yet no one, no one I know gives a rip about vector. All they care about is heading, and a loss of heading freaks them the hell out.

Vector is the ultimate reason why I hate ABS. There are times, even when I'm in my glorious RWD with which I have supreme control, that I get into a situation that I just can't save. This often happens in the wet snow and powdered snow scenarios we discussed earlier, where there exists extreme transitions of surface type. The rear starts waggling, and I just can't keep up with corrections as it switches from bare pavement to thick snow. I start to waggle and can't stop, the waggles are getting worse, I know I won't be able to stop them, and something needs to be done.

What I need to do is completely remove the steering input. I need all of that 100%, part of which is causing my tires to catch and turn me, to be used somewhere else. And the only way to get all 4 to do that is to lock every one of them up. As my heading is swapping back and forth, my vector lags along behind it. Slide to the left, my vector tries to go left. Slide to the right, it tries to go right. And every time it swaps, there's a sweet spot in the middle where the vector returns to dead straight on before continuing to the left or right. If I stomp the brakes right at that moment, all 100% will be used for braking, leaving nothing left for turning, and I'll slide exactly the direction I mean to go.

Sure, often times I'll be facing the other lane or the trees when this happens, but heading means nothing. What matters, the only thing that matters, is vector. Locking up those tires preserves and locks in my vector while at the same time ceasing the heading swaps that I'm unable to correct. Sometimes, it gives me that precious moment I need to get on top of the heading and I can release the brakes, reestablishing the heading. At the very least, I can ride the entire thing out until I come to a complete stop and start all over again.

In ABS, this is impossible. No matter how hard you mash, the ABS will keep those tires rolling and keep your turning forces active. Get into a swap of death with ABS... and you are dead. Or at least in a ditch.

That's all for now. I might come back if I think of more, perhaps the upcoming race season will jar some lost knowledge loose and I'll post it up. Until then... thanks for reading! =)

Quote: Face

Go for it. I'd surely share my own, as I have no shortage of asshats to laugh at who do similar stuff ;)

Sadly I typed in the entire story but either didn't hit save correctly or it was flagged. Lets just say it involved a guy spending over $20,000 on all kinds of tools to "restore" a car worth at best $6,000. I will be happy to buy you a cup of coffee and discuss next time I am on the reservation.

No, it's here. Was so good I had a mod make it is own thread, as I also have gripes about the idiotic things done involving cars

Quote: Face

No, it's here. Was so good I had a mod make it is own thread, as I also have gripes about the idiotic things done involving cars

So I am not nuts, thanks. The offer for more car stories over coffee stands.

Quote: Face

It is entirely obvious that the majority of people think driving consists of "go, stop, and turn" with no thought into how to do these things effectively or how they even happen.

You bet its go stop and turn... Anyone puts a tachometer in a car should be shot. Manual transmissions should be about as socially acceptable as used hypodermic needles and why won't those girls in short shorts from the next car come over and check my tires for me?