Myths of Winter Tire PSI

Sulley

Feb 18, 2023

In the throes of another snowstorm, I was reminded this morning that the new tires I had put on a while ago were overinflated to compensate for below zero temperatures at the time. We have now swung about 40 degrees in the other direction, and my tires have not been performing as well at the 44 PSI they were at earlier today. Dropping to a comfortable outdoor 34/35 PSI greatly improved traction. Here’s why.

There’s an old urban legend that you should over-inflate your tires in the winter, because it distributes more weight to the road. Anyone who skis will tell you how untrue this is, in that a wider set of skis generally is more aggressive by providing more grip on the snow than a narrow pair of skis. Surface area gives traction. But there’s another reason this is especially not true for tires.

Any decent set of tires has siping along the width of the tire, along the tread blocs and usually near the edges of the tire as well. This is particularly the case for three-peaks rated tires. That siping gives your tire extra grip in the snow. Guess what happens when you overinflate your tires? It makes them rounder. This causes the siping around the edges to make less contact with the road, REDUCING the amount of grip your tire has. You may be putting more weight on that narrow set of skis, but they are in fact more ski-like too than they were designed to be without the benefit of the extra siping. Keeping your tires inflated properly, but not overinflated, allows the siping across the entire width of the tire to make good contact with the road.

If you are running your tires in the snow above 35 PSI, consider lowering the pressure down to flatten the tire out. You should notice an improvement in the amount of traction your vehicle gets in snow and slush.

Dr Detroit, Deano Bronc

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Feb 18, 2023

My dad always lowered the tire pressure in the winter. Not a lot, but you post brought back memories 🙂

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Sven, Bluestreak57

Feb 18, 2023

I'm running 30psi in my factory sas tires and the ride and traction is fantastic...I haven't been off ice/snow packed roads since November.

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Deano Bronc

Feb 27, 2023

Sven
I'm running 30psi in my factory sas tires and the ride and traction is fantastic...I haven't been off ice/snow packed roads since November.

Got another cold snap here and some snow. Tires dropped to 32 psi, traction is excellent. I’d drop them lower, but we have pretty big swings and they’ve gotten as low as 28 on their own.

Sven

Feb 27, 2023

I am in south central Texas the only frozen precipitation we drive on is hail. So I know next to 0 about snow driving. But wouldn’t there be a certain situations were you would want a narrow “pizza cutter” tire to cut through the snow. Like maybe 6” of snow you can cut through to reach the road surface underneath. I could see deeper snow you would want to ride on top like snow shoes. Not arguing just really curious, snow scares me.

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Feb 27, 2023

Jakob1972
I am in south central Texas the only frozen precipitation we drive on is hail. So I know next to 0 about snow driving. But wouldn’t there be a certain situations were you would want a narrow “pizza cutter” tire to cut through the snow. Like maybe 6” of snow you can cut through to reach the road surface underneath. I could see deeper snow you would want to ride on top like snow shoes. Not arguing just really curious, snow scares me.

Less pressure = bigger foot print =better traction

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Feb 27, 2023

tstarks
Less pressure = bigger foot print =better traction

Wouldn't that only be true in certain situations?

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Feb 27, 2023

Jakob1972
I am in south central Texas the only frozen precipitation we drive on is hail. So I know next to 0 about snow driving. But wouldn’t there be a certain situations were you would want a narrow “pizza cutter” tire to cut through the snow. Like maybe 6” of snow you can cut through to reach the road surface underneath. I could see deeper snow you would want to ride on top like snow shoes. Not arguing just really curious, snow scares me.

Yes, you're right. There are situations where you don't want a bigger footprint. People sometimes post in what appears to be absolutes, so I'll preface this with "in general" you want a bigger footprint where there is good traction (dry surfaces). In general, you want a smaller footprint where there is less traction, think snow or water. This can be misleading as snow can be wet or dry, loose and powdery or packed and slick. It is a changing surface, so one answer is hard to give that applies in more than that one instance.

If you have a large footprint, you are more likely to hydroplane. On snow and ice, there are times that a wider footprint is better, but other times you may want to (pizza) cut down to the sub-surface that might provide a more firm grip.

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Sven, jimFish

Feb 27, 2023

AcesandEights
Wouldn't that only be true in certain situations?

In what winter situation don't you think this is true?

Feb 27, 2023

AcesandEights
Yes, you're right. There are situations where you don't want a bigger footprint. People sometimes post in what appears to be absolutes, so I'll preface this with "in general" you want a bigger footprint where there is good traction (dry surfaces). In general, you want a smaller footprint where there is less traction, think snow or water. This can be misleading as snow can be wet or dry, loose and powdery or packed and slick. It is a changing surface, so one answer is hard to give that applies in more than that one instance.

If you have a large footprint, you are more likely to hydroplane. On snow and ice, there are times that a wider footprint is better, but other times you may want to (pizza) cut down to the sub-surface that might provide a more firm grip.

I'm not sure you're correct here. A larger footprint means more tread, which means you can tread more water underneath the tire; that should reduce your tendency to hydroplane. So they will increase the threshold at which your tires become waterlogged. Once waterlogged, they'll hydroplane just as much as any other depending on vehicle weight and so forth. With a low profile tire (with more shallow tread), I can see what you're saying having some merit to it - but these tires are far from low profile. You'll also have more siping making contact with the ground which is good for traction. Good wide tires can be just as, or more, resistant to hydroplaning, if they're designed right.

jimFish, AcesandEights

Feb 27, 2023

#10

Sulley
In what winter situation don't you think this is true?

The post I quoted didn't say in winter situations, but it wouldn't be true in any situation where you wanted more contact pressure.

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Feb 27, 2023

#11

Sulley
I'm not sure you're correct here. A larger footprint means more tread, which means you can tread more water underneath the tire; that should reduce your tendency to hydroplane. You'll also have more siping making contact with the ground which is good for traction.

Now even though we do not get a lot of rain here about 33" a year we get most of it in about 5 rain storms a year. seriously 8"/hour storms. And wider tires will get you floating on top and you will hydroplane easier skinnier tires will be your friend.

Laura, Sven

Feb 27, 2023

#12

Jakob1972
Now even though we do not get a lot of rain here about 33" a year we get most of it in about 5 rain storms a year. seriously 8"/hour storms. And wider tires will get you floating on top and you will hydroplane easier skinnier tires will be your friend.

Even if that were true (which I think is more of an urban legend than anything), any effect likely does not outweigh the benefits of having the wider tire's extra tread and siping. The Bronco's wheels are so big that any width is likely to be "wide enough" to fall into this category. I've hydroplaned in heavier SUVs with 245/70's, which are much narrower than anything people are running on Broncos. Yukon XL has about 1,000 lb or more weight over the Bronco, and narrower tires (usually 245s or 265s). Plenty of pressure there - far more than you'd shift around by airing up or down. The width of the tire is largely insignificant here compared to the treat depth, pattern, and most importantly - speed. Airing up your tires is only a false sense of security. Drive slow in the rain and wear good tires. Airing them up won't buy you anything significant.

Laura, jimFish

Feb 27, 2023

#13

Yes tread depth for sure is the biggest factor. I don't know what I was thinking I was comparing regular road tires not AT/MTs which have much deeper tread.

Deano Bronc

Feb 27, 2023

#14

When I intentionally go up to play in the snow, I'll usually air down to about 15-16psi on my stock Squatch tires (no beadlock)... I've been told I could go as low as 10-12, but you're at higher risk of de-beading the tire if you are turning and hit something under the snow, so I'll keep it to 15ish - it does make a HUGE difference in the deeper snow... plus ride quality is nicer, and you have less risk of puncturing a tire if there's a rock or something hidden by the snow.

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Laura, BuckYeah

Feb 27, 2023

#15

Jakob1972
Now even though we do not get a lot of rain here about 33" a year we get most of it in about 5 rain storms a year. seriously 8"/hour storms. And wider tires will get you floating on top and you will hydroplane easier skinnier tires will be your friend.

You're right again. A tire hydroplanes because it cannot displace the water faster than it passes over/through it, so it floats, goes up on "plane". A narrower tire does this, displacement, faster than a wider tire.

It's not an urban legend, but fact. The "tread" of a wider tire is a detriment, not a benefit. It's actually the lack of tread, which allows water to run through that groove (non-tread area), or to the outside of the tire, which allows the tread to make contact with the asphalt.

Less tread (siping) is what helps allow the water to move out of the way of the tread. "Extra tread and siping" is mutually exclusive. The extra tread of a wider tire is a detriment and the extra siping is a misnomer. It's like saying the extra voids, or the extra lack of tread. The extra lack of tread is nothing but space, it doesn't help because it doesn't exist. Where it doesn't exist, it is less wide, haha, meaning a narrower tire is better. It's akin to asking for no ketchup and the restaurant being so kind as to only charge $0.25 for extra no ketchup. Or man, this burger tastes so good without ketchup, I'll order the next one with extra no ketchup. I guess a better way of putting it, in this context, is the lack of extra tread on the narrower tire works better than the actual extra tread of the wider tire.

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Feb 27, 2023

#16

AcesandEights
You're right again. A tire hydroplanes because it cannot displace the water faster than it passes over/through it, so it floats, goes up on "plane". A narrower tire does this, displacement, faster than a wider tire.

It's not an urban legend, but fact. The "tread" of a wider tire is a detriment, not a benefit. It's actually the lack of tread, which allows water to run through that groove (non-tread area), or to the outside of the tire, which allows the tread to make contact with the asphalt.

Less tread (siping) is what helps allow the water to move out of the way of the tread. "Extra tread and siping" is mutually exclusive. The extra tread of a wider tire is a detriment and the extra siping is a misnomer. It's like saying the extra voids, or the extra lack of tread. The extra lack of tread is nothing but space, it doesn't help because it doesn't exist. Where it doesn't exist, it is less wide, haha, meaning a narrower tire is better. It's akin to asking for no ketchup and the restaurant being so kind as to only charge $0.25 for extra no ketchup. Or man, this burger tastes so good without ketchup, I'll order the next one with extra no ketchup. I guess a better way of putting it, in this context, is the lack of extra tread on the narrower tire works better than the actual extra tread of the wider tire.

The spaces in the tread are the channels the water is expunged through. Deep channels means it can “tread” more water out of the tire. Nothing wrong with a wide tire if the tread can evacuate enough water. It’s the tires of any width that don’t channel water well that you have to worry about.

We will have to agree to disagree on this topic. But let’s all at least agree this has nothing to do with snow.

Calgecko

Feb 28, 2023

#17

It's not about the depth of the channels, it's about the design. That's why a "mud" tire isn't inherently great in rain. The tread depth is great, the traction in wet conditions isn't (necessarily). A "rain" and "snow" tire have purposely designed channels, regardless of having less depth than a mud tire. It channels water away. Tread depth has nothing to do with how the water is channeled away as the tire travels through water.

Sorry, still can't agree. It does have to do with snow. You don't get a snow rated tire without sipes.

I'm sorry if this is too personally-directed, but you don't know what you're talking about.

We can agree on this maybe. I don't think it's really worth discussing any more. People should do research outside this thread, because you're ill-informed.

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Feb 28, 2023

#18

AcesandEights
It's not about the depth of the channels, it's about the design. That's why a "mud" tire isn't inherently great in rain. The tread depth is great, the traction in wet conditions isn't (necessarily). A "rain" and "snow" tire have purposely designed channels, regardless of having less depth than a mud tire. It channels water away. Tread depth has nothing to do with how the water is channeled away as the tire travels through water.

Sorry, still can't agree. It does have to do with snow. You don't get a snow rated tire without sipes.

I'm sorry if this is too personally-directed, but you don't know what you're talking about.

We can agree on this maybe. I don't think it's really worth discussing any more. People should do research outside this thread, because you're ill-informed.

I guess if you’re going to resort to personal attacks, I’ll put you on ignore. Bye now.

Feb 28, 2023

#19

Facts on Siping
https://en.wikipedia.org/wiki/Siping_(rubber)
Overinflating tires generally provide only one benefit: it will reduce rolling resistance slightly, improving fuel economy. Otherwise, there is no point in overinflating tires. I've never heard of someone doing that in the winter.
Keeping tires at the specified air pressure will provide the expected balance between fuel economy, comfort, and traction. Reducing air pressure such that the tire can relax, can result in increased friction and thus traction, though can negatively impact tire life and increase heating of the carcass.

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