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In snow in the winter, slamming on the brakes actually can prevent you from stopping your car. I grew up in Minnesota, where you learn how to deal with this ver

In snow in the winter, slamming on the brakes actually can prevent you from stopping your car. I grew up in Minnesota, where you learn how to deal with this very quickly. If you've never driven in snow/ice before, there's a situation where the brakes can "lock up", causing your tires to freeze instead of slowly spin down. For some physics reason I don't entirely understand, the tires have better friction with a slippery surface when they're still spinning, so when they stop spinning your car just turns into a giant hockey puck, and you can no longer stop the car without getting the tires to spin again. Newer cars have what's called an "Anti-Lock Braking System (ABS)", but it usually doesn't work very well. I'm pretty sure it's just there for the people that have never driven in snow before. It's actually worse to trigger it sometimes. If you've never driven in snow before and just moved to a place where it does, find an empty driveway and learn how to pulse the brakes. Seriously could save your life.

sidcool 12y ago
I am looking for the `\s` in your comment.
pedrocr 12y ago
> For some physics reason I don't entirely understand, the tires have better friction with a slippery surface when they're still spinning Nothing complex about this, the coefficient of friction in most reasonable cases is higher when the two surfaces aren't sliding. >Newer cars have what's called an "Anti-Lock Braking System (ABS)", but it usually doesn't work very well. I'm pretty sure it's just there for the people that have never driven in snow before. It's actually worse to trigger it sometimes. ABS is far from new. It was introduced in airplanes in the 1930s and has existed in cars since the 1970s. It's rare for cars these days not to have it. It's also much safer than pulsed braking because the anti-lock feature is applied per-wheel and not globally, so you can safely steer for example. Apparently ABS reduces braking distances on asphalt and may increase them on snow/gravel because in some of those situations locked wheels can actually brake more by digging into the surface. More modern systems probably fix that and I bet even the old ones are still safer in real situations where you need to brake and steer. https://en.wikipedia.org/wiki/Anti-lock_braking_system https://en.wikipedia.org/wiki/Anti-lock_braking_system
chrisBob 12y ago
Threshold breaking, where you stop as hard as you can with out locking up the wheels, is probably better than relying on ABS, but it requires training and practice, and doesn't enable the per-wheel breaking that modern ABS provides. My parents taught me that ABS is often bad, and that sometimes it actually prevents you from stopping (for example on a hill), but then I sat in a car for a demonstration of the difference: I visited the Consumer Reports test track in college, and among other things they had us all put on helmets, and 3 at a time we rode along in a car they had modified to disable ABS with a switch. They had a section of road setup so that one side is slicker than the other, and they straddled the line between that and the regular pavement for their demonstration. The first run, with ABS on, was a hard, but boring stop where the car leaned forward and came to rest nicely. Then they flipped the switch and did the same thing again. Riding along with ABS off was much more exciting. It meant you got be be in the Subaru as it spun around 3 times at 50mph. I was convinced.
bryanlarsen 12y ago
Modern ABS systems work a lot better on snow/ice than older ones. They appear to pulse at an adaptive rate -- if you are on ice/snow they pulse a lot slower than they do on pavement. But your main point stands: don't wait until you're in an emergency situation to find out if your car can stop well on snow/ice.

sidcool 12y ago

I am looking for the `\s` in your comment.

pedrocr 12y ago

> For some physics reason I don't entirely understand, the tires have better friction with a slippery surface when they're still spinning Nothing complex about this, the coefficient of friction in most reasonable cases is higher when the two surfaces aren't sliding. >Newer cars have what's called an "Anti-Lock Braking System (ABS)", but it usually doesn't work very well. I'm pretty sure it's just there for the people that have never driven in snow before. It's actually worse to trigger it sometimes. ABS is far from new. It was introduced in airplanes in the 1930s and has existed in cars since the 1970s. It's rare for cars these days not to have it. It's also much safer than pulsed braking because the anti-lock feature is applied per-wheel and not globally, so you can safely steer for example. Apparently ABS reduces braking distances on asphalt and may increase them on snow/gravel because in some of those situations locked wheels can actually brake more by digging into the surface. More modern systems probably fix that and I bet even the old ones are still safer in real situations where you need to brake and steer. https://en.wikipedia.org/wiki/Anti-lock_braking_system https://en.wikipedia.org/wiki/Anti-lock_braking_system

chrisBob 12y ago

Threshold breaking, where you stop as hard as you can with out locking up the wheels, is probably better than relying on ABS, but it requires training and practice, and doesn't enable the per-wheel breaking that modern ABS provides. My parents taught me that ABS is often bad, and that sometimes it actually prevents you from stopping (for example on a hill), but then I sat in a car for a demonstration of the difference: I visited the Consumer Reports test track in college, and among other things they had us all put on helmets, and 3 at a time we rode along in a car they had modified to disable ABS with a switch. They had a section of road setup so that one side is slicker than the other, and they straddled the line between that and the regular pavement for their demonstration. The first run, with ABS on, was a hard, but boring stop where the car leaned forward and came to rest nicely. Then they flipped the switch and did the same thing again. Riding along with ABS off was much more exciting. It meant you got be be in the Subaru as it spun around 3 times at 50mph. I was convinced.

bryanlarsen 12y ago

Modern ABS systems work a lot better on snow/ice than older ones. They appear to pulse at an adaptive rate -- if you are on ice/snow they pulse a lot slower than they do on pavement. But your main point stands: don't wait until you're in an emergency situation to find out if your car can stop well on snow/ice.