4 ms·

Snow tires are a big help for getting going. They are much less help for stopping.

by graycat 8y ago

Hamuko 8y ago
This is so incorrect it hurts.
- graycat 8y ago
  My point is clear if just consider a little of how snow tires work: The main point is the big bumps in the tread. These big bumps permit spinning drive wheels to dig down in the snow to find some traction, maybe the hard surface below. This digging down has the bumps grab a lot of snow and throw it back and out of the way and let the tires get down, through the snow into some traction. Ordinary tires just spin and throw far too little snow. Works great. But in stopping, there is no such "spinning" or "digging". Instead, all the snow tires can do is roll or slide. So, snow tires help a lot in going but not much in stopping. Typically get into winter car wrecks from not stopping, not from not going. So, once snow tires have you going, be darned careful about stopping -- the risk is not stopping, and snow tires aren't much help because the lugs don't get a chance to dig and throw snow.
  - rjsw 8y ago
    Modern snow tyres don't have big bumps in the tread.
    - graycat 8y ago
      The ones on my car do.
  - Tor3 8y ago
    >"My point is clear if just consider a little of how snow tires work: The main point is the big bumps in the tread. These big bumps permit spinning drive wheels to dig down in the snow to find some traction, maybe the hard surface below. " That's not how snow tires work. Not at all. Independent of the design. And no, they don't 'stop' the way you describe either.
nkurz 8y ago
To the contrary, "winter tires" actually have comparable benefits for stopping. Here's are the first three findings (of ten) from a recent University of Michigan report: Finding #1: The main benefit of winter tires is improved tire adhesion, braking and cornering performance–not acceleration performance. Finding #2: Winter tires provide improved traction on roads that are below 7 °C (45 °F) even when snow and ice are not present. Finding #3: Stopping-distance performance of winter tires on packed snow is typically about 35% shorter than all-season tires and 50% shorter than summer tires. http://umich.edu/~umtriswt/PDF/SWT-2016-10.pdf http://umich.edu/~umtriswt/PDF/SWT-2016-10.pdf
- graycat 8y ago
  I agree, but "winter tires" are quite different from "snow tires". Moreover, I was implicitly assuming that the stopping would be on snow, and not packed snow but, say, just snow as it fell although maybe a minute ago to several days ago. For stopping on wet or slushy streets or just, say, 1-2 inches of snow, then, sure, "winter tires" not only help stopping but likely are better than snow tires. But when my driveway has 8" of fresh snow, to get out I need snow tires, tire chains, or a tractor to pull me out. Then in stopping, say, from 30 MPH in such snow, nothing helps much except tire chains and there are questions about those. Again, what is good about snow tires is that the big bumps on the tread let the tire, when it is spinning trying to drive the car, dig into the snow, kick it backwards out of the way, and let the rubber meet the road. For that, the aggressive tread, with the bumps, is essential. But the bumps work because the tire is spinning and digging, and that action won't work for stopping unless, say, going forward with, somehow, the drive wheels spinning in reverse. The advantages of "winter tires" are how the tread cuts through water and thin layers of snow and has softer rubber with a better coefficient of friction when the rubber does meet the road.
  - rjsw 8y ago
    I have driven in 8" of fresh snow with winter tyres, more than once, they work well. I do remember my grandparents having tyres with deep treads but that kind of thing isn't common in Europe.

Snow tires are a big help for getting going. They are much less help for stopping.

Hamuko 8y ago

This is so incorrect it hurts.

graycat 8y ago
My point is clear if just consider a little of how snow tires work: The main point is the big bumps in the tread. These big bumps permit spinning drive wheels to dig down in the snow to find some traction, maybe the hard surface below. This digging down has the bumps grab a lot of snow and throw it back and out of the way and let the tires get down, through the snow into some traction. Ordinary tires just spin and throw far too little snow. Works great. But in stopping, there is no such "spinning" or "digging". Instead, all the snow tires can do is roll or slide. So, snow tires help a lot in going but not much in stopping. Typically get into winter car wrecks from not stopping, not from not going. So, once snow tires have you going, be darned careful about stopping -- the risk is not stopping, and snow tires aren't much help because the lugs don't get a chance to dig and throw snow.
- rjsw 8y ago
  Modern snow tyres don't have big bumps in the tread.
  - graycat 8y ago
    The ones on my car do.
- Tor3 8y ago
  >"My point is clear if just consider a little of how snow tires work: The main point is the big bumps in the tread. These big bumps permit spinning drive wheels to dig down in the snow to find some traction, maybe the hard surface below. " That's not how snow tires work. Not at all. Independent of the design. And no, they don't 'stop' the way you describe either.

nkurz 8y ago

To the contrary, "winter tires" actually have comparable benefits for stopping. Here's are the first three findings (of ten) from a recent University of Michigan report: Finding #1: The main benefit of winter tires is improved tire adhesion, braking and cornering performance–not acceleration performance. Finding #2: Winter tires provide improved traction on roads that are below 7 °C (45 °F) even when snow and ice are not present. Finding #3: Stopping-distance performance of winter tires on packed snow is typically about 35% shorter than all-season tires and 50% shorter than summer tires. http://umich.edu/~umtriswt/PDF/SWT-2016-10.pdf http://umich.edu/~umtriswt/PDF/SWT-2016-10.pdf

graycat 8y ago
I agree, but "winter tires" are quite different from "snow tires". Moreover, I was implicitly assuming that the stopping would be on snow, and not packed snow but, say, just snow as it fell although maybe a minute ago to several days ago. For stopping on wet or slushy streets or just, say, 1-2 inches of snow, then, sure, "winter tires" not only help stopping but likely are better than snow tires. But when my driveway has 8" of fresh snow, to get out I need snow tires, tire chains, or a tractor to pull me out. Then in stopping, say, from 30 MPH in such snow, nothing helps much except tire chains and there are questions about those. Again, what is good about snow tires is that the big bumps on the tread let the tire, when it is spinning trying to drive the car, dig into the snow, kick it backwards out of the way, and let the rubber meet the road. For that, the aggressive tread, with the bumps, is essential. But the bumps work because the tire is spinning and digging, and that action won't work for stopping unless, say, going forward with, somehow, the drive wheels spinning in reverse. The advantages of "winter tires" are how the tread cuts through water and thin layers of snow and has softer rubber with a better coefficient of friction when the rubber does meet the road.
- rjsw 8y ago
  I have driven in 8" of fresh snow with winter tyres, more than once, they work well. I do remember my grandparents having tyres with deep treads but that kind of thing isn't common in Europe.