Why? Simple. They think he might be a nutcase. It seems that Brian's grandfather taught Brian to zig-zag while braking, to increase the distance on the road, thereby making braking safer. In theory.
Tom and Ray thought he ran the risk of losing control of the car. What do you think? Is there any validity to this slalom theory of braking? We'd love to hear it, if you've ever crossed paths with this unique-- and highly whacko sounding-- theory of braking.
P.S. Want to catch the details? Hear Brian’s call with Tom and Ray right here.
Unless the driver zig zags from one side of a really wide 6 lane highway to the other and back again, he won’t increase the distance enough to matter.
If you zig zag downhill, you effectively have a less steep gradient to climb or coast down, in fact, that’s why mountain roads often zig zag. When I ski downhill, zig zagging is the most effective way to control my speed. Also, when I was a kid with a single speed bicycle, I found that one particularly steep hill was easier to climb if I zig zagged up it.
Also some high performance sailboats, catamarans in particular, will go down wind faster if you zig zag instead of just letting it run dead down wind.
It makes no sense to zig zag. The contact patch on the tire is good for only so much traction in any direction. When braking the contact patch is all being used for deceleration. If you brake and turn you spend some of the traction on turning, not braking, so the braking force is less. Sure you might create a longer distance to brake, but with less braking force. Due to efficiency losses, turning and braking will always take further to come to as stop than in a straight line. The optimum braking is in a straight line. This is why race cars brake in a straight line, then turn without accelerating or braking, this makes maximum use of the tire contact patch in all phases in a turn. It also explains why if you have an underpowered dodge dart, the only way to spin the wheels is in a turn (or in a turn when it’s wet, or in a turn when it’s wet while the tires are on a stripe…).
Traction control and ABS were specifically designed to allow you to BRAKE IN A STRAIGHT LINE!!!
Zigzagging begs you to lose control of the car. Having good winter tires and slowing before going downhill down are two good SANE ways of braking safely.
Anybody who drives in snow country learns that the way to stop a skid is to turn into the skid, which gives you the tranction to regain control–with the wheels pointed in the same direction that the car is moving. Tire treads are designed to grip in the line of travel, and zigzagging is a recipe for a skid,I wonder how often Grandpa has been all over a road without having any idea how it happened–or if he has been very lucky and lives in a warm, dry place.
Hi, I’m writing from Switzerland. Here they offer a thing called a “Schleuderkurs” which is basically lessons on what to do if your car starts to go out of control due to a slippery road - one covered with water, snow or ice - for example. My husband took this course once and this steering back and forth quickly sounds a little like what they taught him to do if your car is going into a spin - except you must keep your foot OFF the brake (which is really hard to do, since all your instincts are telling you to stop the car as soon as possible)!
Sounds to me like maybe Brian’s grandfather came from some snowy or high altitude country where HIS father or grandfather taught him something like this, and eventually over the years the information became warped to this zig-zag breaking idea…
I’m guessing it was because back in his grandfather’s day the brakes were shaft-engaged drum brakes that were hard to balance and really not very powerful. That’s well before my time, but I think the brakes of yesteryear couldn’t provide anywhere near enough friction to lock the front wheels. Perhaps back in the day scrubbing the front tires back and forth was a common way to add more drag than the meager brakes can provide, like slaloming on a ski slope. Of course nowadays it’s totally bogus.
I’m thinking grandpa was a cop. He once pulled over a drunken wacko who was weaving all over the road. The drunk then explained his erratic weaving as a “strategy” to increase braking effectiveness. Grandpa bought that story, thanked the drunk and sent him on his way. That’s my story and I’m sticking to it.
I remember a funny movie with Peter Falk and Charles Grodin called The In-Laws. Falk, a CIA agent, was often being shot at and he instructed his son-in-law to ‘Zig Zag’, which would make you a more difficult target to hit. So, although zig zagging your car might be foolish in most instances, it sounds like a good idea if you are being hailed upon by bullets.
This is just a variant of a classic first-year physics problem!
The problem: if you are heading perpendicular towards an infinitely-long wall at the edge of a parking-lot, is it better to brake in a straight line, turn your car as hard as you can, or some combination of both?
The answer has to do with the maximum acceleration (deceleration) your tires can give before they lose their grip (the simple straight-line braking solution) -vs- the amount of centripetal acceleration required to push/pull your car into a curve. Do the math - it takes more acceleration to turn in a circle of radius R (and thus not hit the wall) than it does to stop in distance R.
Zig-zag is ALWAYS more-likely to lose control, and NEVER better for stopping!
The technique grandpa is referring to is called “scrubbing off speed”. However, standard traffic lanes are no where near wide enough to make this practice effective for normal driving. But you will drive the other motorists around you to think you’ve lost your marbles.
"The answer has to do with the maximum acceleration (deceleration) your tires can give before they lose their grip (the simple straight-line braking solution) -vs- the amount of centripetal acceleration required to push/pull your car into a curve. Do the math - it takes more acceleration to turn in a circle of radius R (and thus not hit the wall) than it does to stop in distance R. "
I did the math and you’re right. The required acceleration required to turn a circle with the radius R is exactly twice as much as the amount of acceleration required for a straight line stop in the distance R.
The Zig-Zag theory of braking might not be recommended for a car but in 1967 Vietnam I was personally grateful that it worked for us in a plane….well, with “help” from the pilot then the radar tower. From my book “Who Knew? Reflections on Vietnam” ….where I worked as an American Red Cross “Donut Dolly.”
WHO KNEW…
…when our plane landed in DaNang
that we wouldn’t have any brakes?
It careened from side to side to slow down
but I’d already unlatched my seat belt
in my enthusiasm to get back.
The pilot and I were the only casualties on board.
His head was cut when we hit the radar tower
and the kid in the tower broke both legs
from the plane in his lap.
I almost died…from embarrassment
as I collected bruises and scrapes
going ass over teakettle down the aisle
with my skirt flying around my head.
They say every landing is a controlled crash.
I believe it.
The term “Donut Dolly” is not a joke. 627 of us served in VN between 1965 & 1972. Check out this 5 min. award-winning documentary: <tinyurl.com/24GQ9FA>
Holley Watts
American Red Cross 1966-67
Supplemental Recreational Activities Overseas
(a.k.a. “Donut Dolly”) DaNang, Chu Lai, An Khe, Cu Chi
Holly, I was there 68-69. I didn’t get any donuts but I did get back. I’m glad you did too. I too thank you for being there. I don’t recommend zig zag for cars, though
The criticisms of the zig-zag theory assume thet the brakes on every vechicle are capable of locking the wheels at all speeds and loads. They are not.
On fresh fallen snow a car or truck trying to stop in a straight line may take longer to stop because the front wheels are polishing the tracks that the back wheels are trying to stop in. Getting the car sideways will shorten stopping distances because you will be building a wedge of snow against the sidewalls of the tires.
In fresh fallen snow and glare ice there is so little traction that ABS systems have been shown to INCREASE stopping distances ( there is so little traction that they can’t effectively “read” it ) .
You never turn and brake at the same time. Period. Doing this “slalom” only serves to load up one or the other front tire, risking the tire folding, breaking the bead, and dragging the rim. Breaking while turning, especially with auto makers under inflating tires to improve ride quality, is the largest cause of vehicular roll-overs on our highways - SUVs and cars alike.
