The_Phantom

I installed my snow tires again last week and noticed that the tires were a little more worn in the centers than on the sides. Sign of overinflation, right? So I put less air in than the last few years where I stuck to the factory recomendation of 36 & 44 psi. The tires are Blizzak LM-25s on the Cup 3 wheels from Tire Rack. How much does everyone else inflate their snow tires? Same as for the summer tires?

BruceP

Affirmative here.

jumper5836

No I go 4 lbs lower then summer. Lower pressure also provides more traction.

BruceP

I don't actually think this is true. Lower tire pressure in snow is a practice that comes from concerns about floatation, which wouldn't usually be an issue for our cars. Other than in the really deep stuff, the best traction comes from putting the most tread down. And that comes from higher, not lower, pressures.

Lowering pressures TOO much actually promotes hydroplaning (although I don't think that 4psi qualifies as "too much").

Lerxst

I would think slightly lower inflation would increase the contact patch, as long as the cross section of tread is completely contacting the road.

BruceP

If that were true, it would be a good idea in the summer, too. It's not. Up to a point, higher inflation pressures put more rubber down. I know it sounds counterintuitive, but it's true.

Apologies for the lame article, but I picked this out because of the contact patch pictures.

http://www.canadiandriver.com/articles/pw/laurens.htm

I think you'll find this is pretty consistently the point of view of car and tires companies alike.

missmy993

17" gets 36 around

pongobaz

I keep mine at 36fr 44r, just like the summer tires. No problems last year or this year so far.

1999Porsche911

One the contirbuting factors of tires losing traction in a corner is the flex of the sidewall. When turning, this slight flex caused by the moementum of the wieght of the car "snaps" the tire sideways and allows it to break from the road surface.

For straight driving using a typical summer tread tire, a lower pressure will dig into snow better than tires with a higher pressure. The lower pressure allows the tire to better conform to the terrain. Tires specifically designed for winter driving are made of a softer compound and do not need this lower pressure to dig in.

On ice? No, non studded, non chained tire in the world will save your ***.

BruceP

Sorry, just not true other than for deeper snow than any Porsche will see. It's a myth, born in the 4x4 world where you can get into snow so deep that floatation actually might make a difference. In anything a car will encounter, lower pressures will lose you traction (and, to your earlier point, predictability). Find us a parking lot with a foot or so on it, and I'll bet my pink slip.

My cred is >30 years of lower Great Lakes snowbelt driving (makes Chicago look like NYC), including some recovery work. This weekend, my Rover was rocker-deep in snow a few times, not that unusual where my country place is. Even in it, I run factory recommended pressures (28/46). I would not dream of dropping the pressures unless there was nothing firm under me, e.g. snow off-road, or mud, or sand. Snow on pavement? Nope.

jumper5836

BruceP you are correct except one thing, lower pressures do make your tires have a larger contact patch and can provide more traction on ice, deep snow or sand. Another important factor is that while driving under those conditions your going very very slow.
I am bumping my tires back up to the recommeded pressures. Since I am not driving under extreme conditions.

Lerxst

Gha... a guy from Winnipeg being corrected by someone from Toronto about something winter related... I'll never live this down! My excuse will be I was born in Vancouver

1999Porsche911

Don't assume since I currently live in the Chicago area that i have little snow driving experience. Learned in the mountains more than 40 years ago. The Upper Adirondacks is hardly a place an inexpereinced driver can navigate in the winter. We used to even race ON lake George, both oval and straight


The fact is, a softer, more flexable contact (whether it is a shoe or a tire) will provide for better traction on a suface that is snow covered.


Next time it snows, try running up a snow covered road in your hard soled dress shoes. Then try wearing your good, soft soled deck shoes. Or raise the tire pressure on your lawn tractor and see how much more the tires slip on the lawn. Or, keep your tires at maximum pressure next tme you go to the drag strip and see if your time is better or worse.

dresler

Tire Rack suggested 36/36 for my winter Pirellis.

BruceP

Geez, I don't know where to start with this...

Um, first, you learned 40 years ago? In the 1960s? I have one word for you: radials.

Shoes? Not an apt analogy. We aren't talking about how hard the finish on your tires is, this being the difference in your shoe example. You are trying to tell me that more contact with less pressure (ie underinflated tires) is better than less contact with more pressure (properly inflated tires). If you want to talk about footwear, you'd be right if the snow is deep and there's no accessible firm base (snowshoes), but wrong if you're walking down a snow covered sidewalk (boots).

Drag strip? I think that has something to do with the tire growing with heat and speed, and nothing to do with a soft tire being inherently stickier than a hard one.

Lawn tractor? Actually, my little John Deere handles hills distinctly better with the tires at higher pressure, thanks. The reason they are often run soft on lawn tractors is to minimize damage to the lawn.

I'm sorry, but on this one you are handing out some advice of the 'old wive's tale' variety. I respect your input on lots of stuff, but this is simply untrue, with the sole exception of deep, soft stuff with no underlying hard surface. These cars will never see enough snow to make running the tires soft a good idea, not without a 6" lift. Add the fact that they'll lose a pound for every 10 degree drop in temperature, and you have a foolish strategy for anyone who is prone to drive their car quickly. And maybe wants to stop, the odd time, too.

Anyway, no point in arguing further. They never go anywhere, and there is no irrefutable source around here. So whatever works for you.