Yes you should drop your Tire pressure in the winter. You have a larger tire footprint for and a bit more more traction. Also having more give in the tread of your tire helps to release snow and keep it from building up in your tread. But if you have the summer only tires, I'd say go rent a car for the trip. Don't go below the lowest recommended pressure and don't do any High speed driving (over 90 mph lets say).
Posts by jarry
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You don't actually bite down to the pavement in snow. You have 2 kinds of tire traction Mechanical and Adhesive. Mechanical traction comes from your tires biting into the snow. as long as your tire treads are reasonably clean this is where most of your snow traction comes from. Its why you have no traction on ice, No bite and no adhesion.
Just a note that defy's logic. page 8-35 of the '08 mazda3 owners manual says that Overinflating your tire creates a greater possibility of damage from road hazards.
If you want a stiffer tire for driving in snow, why does siping help you get better traction?
With higher pressure your sidewalls are stiffer which doesn't allow your tire to warm up as much while driving.
The tread section of your tire that is generally designed to help you turn are toward the outer part of the tire and having less weight on those because you have more crown on your tire will lessen your ability to take corners.
A stiffer tire is less able to conform to minor bumps, grooves and irregularities making it more likely to have an instant traction loss.
With a lower pressure you have more Tread distortion which helps keep your tires free of ice buildup and snow and your tires get warmer and stay a bit more pliable.
A wide track with wide grooves help you push more snow out of the contact areas. Floating comes from not having enough voids in your tire or having your voids iced up completely.
If you want a stiffer tire for driving in snow, why does siping help you get better traction?
With higher pressure your sidewalls are stiffer which doesn't allow your tire to warm up as much while driving.
The tread section of your tire that is generally designed to help you turn are toward the outer part of the tire and having less weight on those because you have more crown on your tire will lessen your ability to take corners.
A stiffer tire is less able to conform to minor bumps, grooves and irregularities making it more likely to have an instant traction loss.
With a lower pressure you have more Tread distortion which helps keep your tires free of ice buildup and snow and your tires get warmer and stay a bit more pliable.
A wide track with wide grooves help you push more snow out of the contact areas. Floating comes from not having enough voids in your tire or having your voids iced up completely.
Btw I'm an engineer for a tire company.
Seems like almost everyone who has commented here has relied on secondary information. They read it on a site somewhere or its "common knowledge." I appreciate that you were posting information in an attempt to answer someones questions but if you don't actually know, or you are referencing some other information you found or saw someone else, at least qualify your response so that people can evaluate it. Even though I'm an engineer I don't assume I know everything there is to know, and when I put out my opinion I make sure its labeled as an opinion.
After posting my comments here, I asked the questions because I was interested to see where everyone is getting their information from. I went digging around the internet and couldn't find much of anything. There really isn't anything anywhere on how winter tires work and why they work. If you do find references to snow driving and tire pressure, go ahead and link them.
Siping is made to trap very small pockets of snow and ice because nothing adheres better to snow and Ice than more snow and Ice. If you question this go make a snowball, and then try to stick it to something else. This goes back to Adhesive vs Mechanical traction.
Rubber has a low heat transfer rate so even though it is in the "freezing snow" the tires are in fact well above the temp of the snow. Tires tend to hold in heat and that is actually one of the biggest considerations in designing tires. Deflection of a tires sidewall is a form of work and creates heat. Tire pressure has a huge effect on tire temperature because if your tires are deflecting more they are doing more work and more heat gets stored in the tire.
The racing car with the narrow tires also has spiked and studded tires. So digging through the snow and getting down to ice and possibly ground is much more effective for them. But we don't have spiked studded tires. If it were a real advantage, we'd all have 4 donut spares on for winter driving.
The 4.7 psi drop is from some engineer getting too picky with the numbers.
The idea is to hold your tires at a constant Volume between Summer and Winter. So basic chem, ideal gas law PV=nRT. To hold the V constant ,n and R are the same so P1/V1=constant and you can set the 2 equal. P1/T1 =P2/T2. Temperature has to be in an absolute temp scale so you have to change degrees Fahrenheit to Rankin. If you are looking at the difference in tire pressure from 10F to 80F. 10F=470R, 80f=520r. P2/35= 470/50. P2=31.6 psi which is a drop of 3.6 psi purely from the temp difference. If you measure from 90F to 0F you get a 4.7 psi drop.
Yes you are right, Tread depth tread width and angle are all important. There are literally thousands of tread designs that give a specific advantage in different situations and are less effective in other circumstances. So to discuss tread design specifics is pretty much impossible. We can just talk in generalities.
And then there are lots of mechanisms that testing is the only way to qualify. Tire design is much less exact and less developed than a lot of other engineering. The amount of testing involved in taking a tire from concept to construction is impressive.
Seems like almost everyone who has commented here has relied on secondary information. They read it on a site somewhere or its "common knowledge." I appreciate that you were posting information in an attempt to answer someones questions but if you don't actually know, or you are referencing some other information you found or saw someone else, at least qualify your response so that people can evaluate it. Even though I'm an engineer I don't assume I know everything there is to know, and when I put out my opinion I make sure its labeled as an opinion.
After posting my comments here, I asked the questions because I was interested to see where everyone is getting their information from. I went digging around the internet and couldn't find much of anything. There really isn't anything anywhere on how winter tires work and why they work. If you do find references to snow driving and tire pressure, go ahead and link them.
Siping is made to trap very small pockets of snow and ice because nothing adheres better to snow and Ice than more snow and Ice. If you question this go make a snowball, and then try to stick it to something else. This goes back to Adhesive vs Mechanical traction.
Rubber has a low heat transfer rate so even though it is in the "freezing snow" the tires are in fact well above the temp of the snow. Tires tend to hold in heat and that is actually one of the biggest considerations in designing tires. Deflection of a tires sidewall is a form of work and creates heat. Tire pressure has a huge effect on tire temperature because if your tires are deflecting more they are doing more work and more heat gets stored in the tire.
The racing car with the narrow tires also has spiked and studded tires. So digging through the snow and getting down to ice and possibly ground is much more effective for them. But we don't have spiked studded tires. If it were a real advantage, we'd all have 4 donut spares on for winter driving.
The 4.7 psi drop is from some engineer getting too picky with the numbers.
The idea is to hold your tires at a constant Volume between Summer and Winter. So basic chem, ideal gas law PV=nRT. To hold the V constant ,n and R are the same so P1/V1=constant and you can set the 2 equal. P1/T1 =P2/T2. Temperature has to be in an absolute temp scale so you have to change degrees Fahrenheit to Rankin. If you are looking at the difference in tire pressure from 10F to 80F. 10F=470R, 80f=520r. P2/35= 470/50. P2=31.6 psi which is a drop of 3.6 psi purely from the temp difference. If you measure from 90F to 0F you get a 4.7 psi drop.
Yes you are right, Tread depth tread width and angle are all important. There are literally thousands of tread designs that give a specific advantage in different situations and are less effective in other circumstances. So to discuss tread design specifics is pretty much impossible. We can just talk in generalities.
And then there are lots of mechanisms that testing is the only way to qualify. Tire design is much less exact and less developed than a lot of other engineering. The amount of testing involved in taking a tire from concept to construction is impressive.
If you are driving off road or on a road with very little traffic you encounter unmolested snow and have to worry more about tire float. But most situations you are driving on a road where someone else went before you and you are encountering a hard packed or iced over section of road. Its this type of road that winter tires are designed to manage. If you are cutting a new path through new snow then you need a different approach and the thin studded tires are right for that. But its better to talk about the general strategies where most of us drive every day and not stress about the rare instances.
You say you live in Sweden? Do you guys do full concrete roads over there? Our roads are HORRIBLE here. I was listening to a story today that said 94% of our roads are asphalt
BLAH!!!
Almost everyone in Europe has a summer/winter specific tire and wheel combo for their cars, and in the US its pretty rare that people do (unless they were forced because their MS3 has summer tires). Even in places that absolutely need snow tires people refuse to invest in the extra control and piece of mind. Go buy dedicated snow tires if you are in an area that has a low temp, even if you don't get excessive snow. They offer huge advantages.
The Tire pressure thing is just that, your tire pressure drops when the temperature drops and you have to account for that so check your tire pressure and put it back to the recommended pressure. I even oversimplified the calculation just to demonstrate where it came from. Someone was being a typical engineer and a technical writer was saying "whatever" when they put 4.7 is the exact pressure you need to raise your tires.
You say you live in Sweden? Do you guys do full concrete roads over there? Our roads are HORRIBLE here. I was listening to a story today that said 94% of our roads are asphalt
BLAH!!!Almost everyone in Europe has a summer/winter specific tire and wheel combo for their cars, and in the US its pretty rare that people do (unless they were forced because their MS3 has summer tires). Even in places that absolutely need snow tires people refuse to invest in the extra control and piece of mind. Go buy dedicated snow tires if you are in an area that has a low temp, even if you don't get excessive snow. They offer huge advantages.
The Tire pressure thing is just that, your tire pressure drops when the temperature drops and you have to account for that so check your tire pressure and put it back to the recommended pressure. I even oversimplified the calculation just to demonstrate where it came from. Someone was being a typical engineer and a technical writer was saying "whatever" when they put 4.7 is the exact pressure you need to raise your tires.
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