Between Place Card and Max Cold PSI, where should I be to maximize traction on icy roads (not snow)?
Sleet / Thin Ice on Road, What PSI for Traction?
- Thread starter Jonny Z
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When you walk on ice, or snow, or any slippery hard surface; Do you walk on your tippy toes or do you walk flat footed trying to put as much sole in contact with the "road" as possible?
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Snow requires max ground pressure. Not much you can do. The profile/width of the tire kinda dictates it. Now surely over inflation will give you issues ..but under inflation has its own set of liabilities. You can't constantly be driving on ice and at crawling speeds. Unless you carry on board air ..and are willing to air up and down as needed ...AND KNOW when to do it ..you're far better off just leaving it at the recommended pressure.
Get studded snows on dedicated rims if it's that bad on a seasonal basis where you live. They'll last you 6 or 7 seasons if used that way.
Get studded snows on dedicated rims if it's that bad on a seasonal basis where you live. They'll last you 6 or 7 seasons if used that way.
I live in Austin, TX, we get sleeted once or twice a year. The biggest hazard on the road is not the icy road itself, but the idiots that don't know how to act and end up spinning around and slamming into you. I have decided this year, if it sleets, I will take the road less travelled by: the back two lane country road. It has a few more bridges, and a 30 degree hill.
I like to experiement with tire pressure. My lower limit is the placard valuve, and my upper limit is the max cold PSI on the side wall. I do not intend to ever go out of this range.
Seems from what everyone said, a pressure approaching the lower limit would be yield more benefit.
Thanks for the replies.
I like to experiement with tire pressure. My lower limit is the placard valuve, and my upper limit is the max cold PSI on the side wall. I do not intend to ever go out of this range.
Seems from what everyone said, a pressure approaching the lower limit would be yield more benefit.
Thanks for the replies.
When it comes to ice, it really doesn't matter what the pressure is. There is so little traction you just have to be careful.
I'm going to disagree with oli's analogy - The reason we walk flat footed on ice is that the motion of the foot put forces on the ice, so we put our feet straight down to avoid these forces. So like why old people walk they way they do.
I'm going to disagree with oli's analogy - The reason we walk flat footed on ice is that the motion of the foot put forces on the ice, so we put our feet straight down to avoid these forces. So like why old people walk they way they do.
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I encounter the same thing here in my neck of PA. We get, aside from the occasional good blow from the south, very little in terms of snow. The main problem is too many people in too small a space with none of them having enough practice at winter driving. It totally makes sense ..except that more people should realize their limitations and "learn how to learn" in a more sensible and economical manner.
I'd go through Harrisburg every day in the early hours of the morning. At least 85 bridges (seems that way, anyway) ..and everyone was bumper to bumper on glaze ice @ 5-10 mph. Me? 4 -6 car lengths. Invariably someone would slam on the brakes and fender benders of high number occured. Around me ..vehicle ingress to the four lane was possible and relatively safe. Everywhere else?
I did note your location ..but presented it in a generic manner for those in other climates.
I'd go through Harrisburg every day in the early hours of the morning. At least 85 bridges (seems that way, anyway) ..and everyone was bumper to bumper on glaze ice @ 5-10 mph. Me? 4 -6 car lengths. Invariably someone would slam on the brakes and fender benders of high number occured. Around me ..vehicle ingress to the four lane was possible and relatively safe. Everywhere else?
I did note your location ..but presented it in a generic manner for those in other climates.
Less pressure is better in wet/snow/ice. 28-30 rather than 32-34. At higher pressures, the tires stand-off under load, lower pressures they get wretched down and grab.
I like the idea of having a "longer" contact patch from less inflation. Max inflation might lead to having a traction rectangle, long side perpindicular to the length of the car. Get going sideways, and you have less traction.
Also apparantly the more the lugs flex, the more snow they kick out... but you asked about ice.
Also apparantly the more the lugs flex, the more snow they kick out... but you asked about ice.
I don't think you'll see a bit of difference on ice. Think about it-it's still just as slick no matter how big the "contact patch" is. Ice is ice and slick no matter what. Once you break traction it's all over.
If larger contact patches made any difference, you'd see fewer "bubba buggies" (4X4's with big tires and lift kits) in the ditch during an ice storm.
Even if you reduce the pressure 10# in each tire you are only adding a couple scant square inches to the total contact patch. It will make no difference on ice when a 2500# automobile starts sliding.
As Gary said, the only real way to gain any traction on ice is studded snow tires. Other than that no amount of tinkering with the tire pressure will make any difference.
We get several ice storms each year in Iowa, as well as plenty of snow.
The best defense is to slow down-way down.
If larger contact patches made any difference, you'd see fewer "bubba buggies" (4X4's with big tires and lift kits) in the ditch during an ice storm.
Even if you reduce the pressure 10# in each tire you are only adding a couple scant square inches to the total contact patch. It will make no difference on ice when a 2500# automobile starts sliding.
As Gary said, the only real way to gain any traction on ice is studded snow tires. Other than that no amount of tinkering with the tire pressure will make any difference.
We get several ice storms each year in Iowa, as well as plenty of snow.
The best defense is to slow down-way down.
"If larger contact patches made any difference, you'd see fewer "bubba buggies" (4X4's with big tires and lift kits) in the ditch during an ice storm."
What matters is how much tread with traction is in contact with the ice. The hillbilly BMWs (big mud wagons :^) seem to usually favor big mud terrains, which have lots of voiding and very little if any siping. Decent non studded ice tires seem to have lots of siping with lots of rubber in contact with the road, with voiding not much more than a mud and snow tire. Tires adequate for the conditions seem to usually favor larger contact patches for better traction.
What matters is how much tread with traction is in contact with the ice. The hillbilly BMWs (big mud wagons :^) seem to usually favor big mud terrains, which have lots of voiding and very little if any siping. Decent non studded ice tires seem to have lots of siping with lots of rubber in contact with the road, with voiding not much more than a mud and snow tire. Tires adequate for the conditions seem to usually favor larger contact patches for better traction.
If you put the air pressure too low the center of the tire will bow upwards also creating a lower contact patch...
(why the edges wear when tires are underinflated)
There will also be a much much higher risk of hydroplaning if
you are underinflated even modestly say 24psi vs 32.
(why the edges wear when tires are underinflated)
There will also be a much much higher risk of hydroplaning if
you are underinflated even modestly say 24psi vs 32.
Disagree.
Ah....Mmmm.....I hate to mention this, but doesn't ice turn to water under pressure?
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For snow ..it's simply a matter of ground pressure. Tall and skinny is the way to go. Same with mud with a bottom to it. Mud that's too deep ..as with snow that's too deep...then floation is the name of the game. This is only applicable where with 4wd ..or perhaps something like a VW Golf where most of the mass of the vehicle can be supported by the drive wheels. The other shoe that drops on this scene is that when you have such wide tires that indeed can support the weight of the vehicle without penetration, then you float on ALL surface imperfections. The lighter the vehicle ..the more the terrain effects you. That is, if you can float on the 2' deep snow with little penetration ...rutted snow will tend to direct you where it goes. That "low groud pressure" works both ways. In a pickup, it can make 4WD a mandatory mode just to climb a small incline.
Unless you're driving on a plowed lake for the whole winter, you've got to select your tire based on the most prevalent conditions.
Aside from some place like Iceland ..on dedicated tour buggies..the USA is the ONLY place you see wide traction tires. The Euros and everywhere else their influence has lingered ..tend to go with the tall and skinny.
As far as air pressure..
Although lower pressure will alter your contact patch in terms of evenly distributed ground pressure, the added drag will produce more traction. Try pushing a car with a flat tire sometime.
There's also the matter of going doesn't equate to stopping on ice. I traveled up the NJ turnpike in freezing rain with the "hot lick" of the time, hydrophyle tires, @ 70 mph while everyone else was flashing their lights and blowing their horns as they were doing 35 mph ..but I'd be doing cartwheels if I had had cause to hit the brakes at that speed.
On normal surfaces I'll agree. However I don't think he wants to let all of the air out of his tires.
I'll still contend that letting a few pounds of air out of tires to drive on ice will make no noticeable difference in traction, whether starting, speeding or stopping. The amount of friction provided by the ice is so drastically reduced that there are virtually no benefits.
Try this-in the next ice storm walk outside in dress shoes that are large and flat on the bottom-the largest "contact" patch you can find. Repeat the process with winter boots that have treaded soles-a much more limited "contact" patch, albeit with more tread. By the larger contact patch theory, the dress shoes should get better traction on ice, right?
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I think that there's a material/surface component there that also has an impact.
If you'll note my last post, I'm not a believer in the larger contact patch theory except in certain situations. On ice, you're typically just providing four larger skid pads to slide on ..at least in terms of braking. "Go" is typically easier on ice then "stop".
I'm don't have such great faith in siping. I haven't had cause to really consider it much either(in all fairness). If it's that bad, and they were available in my size, studded snows would be in use if the conditions warranted it. If it's just planning for the exceptional situation ..it makes far more sense to just skip driving for the day. If studs were not available ..and ice was a routine occurance, then siping and all the other beliefs and modalities could be explored. Chains are usually an alternative for the "I gotsta go" crowd.
There are situations where there is no good way to get around things in all conditions all the time. Everyone, understandably, wants a ONE ITEM fix-it. It doesn't exist.
If you'll note my last post, I'm not a believer in the larger contact patch theory except in certain situations. On ice, you're typically just providing four larger skid pads to slide on ..at least in terms of braking. "Go" is typically easier on ice then "stop".
I'm don't have such great faith in siping. I haven't had cause to really consider it much either(in all fairness). If it's that bad, and they were available in my size, studded snows would be in use if the conditions warranted it. If it's just planning for the exceptional situation ..it makes far more sense to just skip driving for the day. If studs were not available ..and ice was a routine occurance, then siping and all the other beliefs and modalities could be explored. Chains are usually an alternative for the "I gotsta go" crowd.
There are situations where there is no good way to get around things in all conditions all the time. Everyone, understandably, wants a ONE ITEM fix-it. It doesn't exist.
Once or twice a year?? STAY HOME!
Bob
Bob
"Once or twice a year?? STAY HOME!"
Or STAY AWAY FROM HOME if one is caught in an ice storm while on the road heading home.
One needs to distinguish between 'hard' ice in cold weather, and 'soft' ice close to freezing. Hard ice responds better to attempts at improving traction, while I've been on soft ice that was so bad that even with 4wd and studded severe snow tires I'd start sliding while I was idling :^)
Or STAY AWAY FROM HOME if one is caught in an ice storm while on the road heading home.
One needs to distinguish between 'hard' ice in cold weather, and 'soft' ice close to freezing. Hard ice responds better to attempts at improving traction, while I've been on soft ice that was so bad that even with 4wd and studded severe snow tires I'd start sliding while I was idling :^)
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When I had my 454/auto C20..I had to remember to make sure that I applied the brakes extra hard after I stopped ..other wise the rear wheels would start spinning on the slick surfaces.
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