lowering tire pressure for icy driving
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I run -2 size front snow tires on steel rims (185 70 14 firestone winterforce) which have soft sidewalls with no filler and I am at about 26psi at 20 deg for decent traction. I Dont think the sidewalls on the dunlops I had on my fit would want to run much below 28 or 29 psi before you're driving on the sidewall filler and worsening the winter steering. Not all tire construction take well to low pressure. I dont think you could loose a bead seal above 20psi unless you whack a curb - but I would not go below 27 psig on the OEM "all weather" ( yeah, right
) tires.
The modern thinking is that you should maintain the recommended tyre pressures for winter tyres, this is because lowering tyre pressures increases braking distance on a cold dry road and some types of ice, it only helps slightly in snow or mud.
Personally I would run OEM recommendation in winter. Come Spring I bump up to 32-35 depending on load.
Turf1 stipulated specifically for very icy conditions, not winter driving in general, and on that score I think he's right.
I've talked to people who've lived WAY up in the north of Saskatchewan & Alberta - places where temps drop under -20 and STAY under -20 for days or weeks at a time - and what many drivers there practice is to decrease pressure in conditions when there's likely to be lots of continuous frozen driving surfaces.
The idea is to spread out the contact area a little more, giving the tread, sipes and compound features the maximum chance to make resistance - the same dynamic which gives under-inflated tires lousy fuel economy in normal conditions is supposed to be beneficial on ice & hard frozen snow.
Once again, this is for special conditions of extreme cold, flash reeze or aftermath of freezing rain.
I've never heard of a bead popping out from underinflation - but you CAN damage it by hitting something. Stock PSI are usually on the low side to begin with, droping more than 5psi starts to undermine the tire's Speed Rating, Load Rating and impcat resistance. It goes without saying that they "baby" the tires when driving them underinflated, which the extreme conditions would call for anyway, being extra alert not to hit any hidden curbs or craters, remebering that your tires are slightly compromised wherever you get clean pavement, and so forth.
It sounds very logical although I haven't really had enough ice & frozen snow where I drive in recent years to evaluate for myself wether it works like they say.
I've talked to people who've lived WAY up in the north of Saskatchewan & Alberta - places where temps drop under -20 and STAY under -20 for days or weeks at a time - and what many drivers there practice is to decrease pressure in conditions when there's likely to be lots of continuous frozen driving surfaces.
The idea is to spread out the contact area a little more, giving the tread, sipes and compound features the maximum chance to make resistance - the same dynamic which gives under-inflated tires lousy fuel economy in normal conditions is supposed to be beneficial on ice & hard frozen snow.
Once again, this is for special conditions of extreme cold, flash reeze or aftermath of freezing rain.
I've never heard of a bead popping out from underinflation - but you CAN damage it by hitting something. Stock PSI are usually on the low side to begin with, droping more than 5psi starts to undermine the tire's Speed Rating, Load Rating and impcat resistance. It goes without saying that they "baby" the tires when driving them underinflated, which the extreme conditions would call for anyway, being extra alert not to hit any hidden curbs or craters, remebering that your tires are slightly compromised wherever you get clean pavement, and so forth.
It sounds very logical although I haven't really had enough ice & frozen snow where I drive in recent years to evaluate for myself wether it works like they say.
Originally Posted By: eljefino
I've seen tires at 5 psi that haven't popped beads. Don't recommend going that low.
Really best thing for that car would be skinny "pizza cutters" at normal ish psi.
Pizza cutters are great in slush and wet snow, but on packed snow, ice, or dry snow, I find wider tires to grip a little better (those conditions need contact area more than pressure, as trying to cut through to the surface underneath isn't as helpful). Plus, the wider tires break free more predictably.
As I've put progressively wider tires on the Jeep, it's gotten better in most kinds of snow and ice (it'll cruise through 6" of unplowed dry snow with 10 - 12" drifts in 2wd like it's nothing, and that's on A/Ts, not snow tires). But, it's only mediocre in wet snow and slush. It'll stop fine as pitching weight onto the nose digs the tires into it harder. However, in 1" of slush, 4wd is pretty much required to get it to move. In 2wd, the lightest throttle feathering possible still results in tons of wheelspin (yet in 3" of dry, semi-packed snow, it'll scoot off the line pretty quickly in 2wd).
Wider vs narrower is a matter of conditions you're likely to see most.
Ideally, the best pressure is whatever will give the most even contact pressure across the tread width. Going lower than that can help when on uneven surfaces, such as rough, uneven, icy, packed snow. The lower pressure will allow the tire to conform to the surface better, which can give better contact and more grip.
I've seen tires at 5 psi that haven't popped beads. Don't recommend going that low.
Really best thing for that car would be skinny "pizza cutters" at normal ish psi.
Pizza cutters are great in slush and wet snow, but on packed snow, ice, or dry snow, I find wider tires to grip a little better (those conditions need contact area more than pressure, as trying to cut through to the surface underneath isn't as helpful). Plus, the wider tires break free more predictably.
As I've put progressively wider tires on the Jeep, it's gotten better in most kinds of snow and ice (it'll cruise through 6" of unplowed dry snow with 10 - 12" drifts in 2wd like it's nothing, and that's on A/Ts, not snow tires). But, it's only mediocre in wet snow and slush. It'll stop fine as pitching weight onto the nose digs the tires into it harder. However, in 1" of slush, 4wd is pretty much required to get it to move. In 2wd, the lightest throttle feathering possible still results in tons of wheelspin (yet in 3" of dry, semi-packed snow, it'll scoot off the line pretty quickly in 2wd).
Wider vs narrower is a matter of conditions you're likely to see most.
Ideally, the best pressure is whatever will give the most even contact pressure across the tread width. Going lower than that can help when on uneven surfaces, such as rough, uneven, icy, packed snow. The lower pressure will allow the tire to conform to the surface better, which can give better contact and more grip.
Why do you think lower pressure gives better traction??
MAYBE if you are stuck - but no way for me.
MAYBE if you are stuck - but no way for me.
Originally Posted By: mechtech2
Why do you think lower pressure gives better traction??
MAYBE if you are stuck - but no way for me.
It can give better traction on snow, but on ice I don't know.
From Continental Tire:
".............Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition..........."
Why do you think lower pressure gives better traction??
MAYBE if you are stuck - but no way for me.
It can give better traction on snow, but on ice I don't know.
From Continental Tire:
".............Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition..........."
The premise is a floppy sidewall makes the tread blocks shrink and expand and fling snow out. We see many but not all snow tires with softer sidewalls.
But we don't always want snow flung out, sometimes we want it to stick to the rubber. Is one of those things where fixing one thing compromises another.
I'd defer to someone who's objectively tested this. My own 2300 lb car needs pizza cutters and seeing 18 wheelers and loaded passenger busses flying through storms with lots of weight on small patches has me in the "dig down through it" camp.
But we don't always want snow flung out, sometimes we want it to stick to the rubber. Is one of those things where fixing one thing compromises another.
I'd defer to someone who's objectively tested this. My own 2300 lb car needs pizza cutters and seeing 18 wheelers and loaded passenger busses flying through storms with lots of weight on small patches has me in the "dig down through it" camp.
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