A debate question - Narrow Vs. Wide tires for winter driving
11-19-2009, 04:06 PM
#11
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Okay, 1/2 point to cb22 for providing the super cool video of WRC racing. I only gave a 1/2 point because I have little doubt those guys are driving with studded tires, to which higher PSI from a narrower tire makes more sense to me.
1-1/2 points to kleinbus for providing real-world experience in which the test involved almost identical vehicles, that and he sounds like he's driven in winter conditions for a long season vs. people in the southern US that get a little taste of it every now and then.
Seeing and hearing about the WRC certainly makes a compelling argument for narrow tires. I'll keep playing the advocate for the other side though just so we can keep having a nice debate about this...
I was just researching patents for snow tires and I noticed a pattern forming. Many patents have a description that indicates that a higher contact area is better for traction on ice, but not so good in deep snow. It appears numerous patents have been trying to deal with this balance. This is leading me to believe that a wider tire *may* be the right tire for certain winter conditions, and bad for other winter conditions. For example, I'm starting to think that people who live in a region where they see more "warm ice" due to temps hovering around 32 degrees a lot might do better with wider tires, while those of us in the snowier regions and below-zero temps with fresh snow daily might do better with more narrow tires that have more spacing between the lugs and more rigid blocks for cornering. Here's some examples of the details I'm finding from the U.S. Patent web site, all related to tire designs for snow and ice...
http://www.freepatentsonline.com/5647926.html
A patent for Bridgestone Corporation
"Motor vehicle tire with a tread profile for a superior grip on snow and ice" Lots of good stuff on this one.
1-1/2 points to kleinbus for providing real-world experience in which the test involved almost identical vehicles, that and he sounds like he's driven in winter conditions for a long season vs. people in the southern US that get a little taste of it every now and then.
Seeing and hearing about the WRC certainly makes a compelling argument for narrow tires. I'll keep playing the advocate for the other side though just so we can keep having a nice debate about this...
I was just researching patents for snow tires and I noticed a pattern forming. Many patents have a description that indicates that a higher contact area is better for traction on ice, but not so good in deep snow. It appears numerous patents have been trying to deal with this balance. This is leading me to believe that a wider tire *may* be the right tire for certain winter conditions, and bad for other winter conditions. For example, I'm starting to think that people who live in a region where they see more "warm ice" due to temps hovering around 32 degrees a lot might do better with wider tires, while those of us in the snowier regions and below-zero temps with fresh snow daily might do better with more narrow tires that have more spacing between the lugs and more rigid blocks for cornering. Here's some examples of the details I'm finding from the U.S. Patent web site, all related to tire designs for snow and ice...
http://www.freepatentsonline.com/5647926.html
"Winter or snow tires have historically been designed with treads having large traction lugs that were widely spaced yielding a very low road contacting surface within the tires normally loaded footprint. These open tread patterns are excellent in deep snow. However, due to the large lugs and open tread pattern these tires are notorious for generating substantial noise and vibration when used on rain soaked or dry paved roads. The tread wear rate is rapid and therefore these tires are considered for use only during the snowy winter months. These tires are not particularly well suited for icy road conditions."
http://www.freepatentsonline.com/5733650.html"Regarding tread patterns of current interest, the applicant has arrived at the conclusion that, when using the invented compound for the wearing surface, the tread pattern may with advantage be designed with less number of grooves, diagonally as well as radially, so leading to an increased contact area between tire and rad surface. This is due to the new compound increasing the adhesion against ice as compared to what has been the fact for tires till now."
"As mentioned before, experiments have shown that tires containing the invented compound in the wearing surface may as well have a relatively bigger pattern contact area"
http://www.freepatentsonline.com/7137424.html"As mentioned before, experiments have shown that tires containing the invented compound in the wearing surface may as well have a relatively bigger pattern contact area"
"In the case of a pneumatic tire used on a snowy road and a frozen road in winter (“ winter tire”, hereinafter), emphasis is placed on driving performance on an especially slippery frozen road. More specifically, there is employed a method in which the land ratio of a tread surface is increased to increase the ground-contact area, or there is employed a method in which the tread central portion having a long ground- contact length in the tire circumferential direction is formed with a rib-like land on which a sipe is disposed. In any of these methods, however, the driving-in-snow performance, especially the driving performance in deep snow is prone to deterioration."
http://www.freepatentsonline.com/6736176.htmlA patent for Bridgestone Corporation
"And also, when a substance being gas at the usual use temperature region of the tire and being liquefied at a lower temperature region of not higher than 0° C. is included in the composite body as a gas B or a third gas C, if the tire is rendered into a lower temperature on snow or ice road in winter season, a part of the included gases is liquefied, whereby the internal pressure of the tire can be lowered. By such a lowering of the internal pressure is enlarged a ground contact area of the tire, which is effective to improve the tire performances on the snow or ice road."
http://www.freepatentsonline.com/5967211.html"Additionally when such fibers or ceramic particles are removed by the friction of the tire on the road, the tire's exposed surface is significantly rougher than that of a tire tread without such additives contained in the tire tread rubber composition. It is readily apparent that a rougher tread surface has a larger surface area for contact with the ice than a smoothly worn traditional tread surface. This is a hypothesis as how improved, or at least enhanced, icy road traction might be obtained for the tire tread."
http://www.freepatentsonline.com/6659146.html"Motor vehicle tire with a tread profile for a superior grip on snow and ice" Lots of good stuff on this one.
"The experts are also familiar with the fact that the coefficient of friction μ increases as the pressure decreases. If the contact surface cannot be enlarged and the mass to be supported cannot be reduced, the pressure should be as constant as possible at least over the available contact surface. In connection with the facts stated in the preceding paragraph, this has led tire experts to the conclusion that measures should be taken for realizing positives similarly soft in the center and on the edge. Although DE-AS 24 32 363 (1981) aims to achieve an improved water discharge from the ground contact surface, a certain softening of the profile pad centers is already achieved with the measures described in this publication."
"...This means that tangential forces, e.g., propulsive or brake forces, result in an increased tilting of the pad sections that are separated from one another by the incisions. Although this slightly improves the grip on snow-covered roads, the coefficient of friction on icy roads which is particularly critical in situations of this type significantly deteriorates because the aforementioned tilting concentrates almost the entire surface pressure on the very small edge surfaces. In other words, the reduced flexural strength eliminates the advantage of a reduced compressive rigidity in the pad center with respect to the most critical aspect of a winter tire, namely the grip on icy roads."
"...The numerous small sinks S at the staggers EV of the incisions E improve the microdrainage from the incisions. This improves the discharge of melt water from the ground contact surface. In contrast to wet roads on which significantly larger quantities of water are introduced into the contact area from the contact area inlet and, as far as possible, discharge in the front third of the contact area, a thin water film is only produced in the contact area itself when driving on ice due to melting. "
"...The thusly created water quantity naturally depends on the ice temperature; warm ice produces relatively large quantities of melt water. This is the reason why it is particularly difficult to drive on roads covered with warm ice.
Although the water quantities in case of warm ice are smaller than those on wet roads, the decrease in grip is particularly significant because the ice is nearly smooth. This means that a very small quantity of water can cause a complete separation of the tread from the solid ground.
In order to improve the most difficult aspect of a winter tiregrip on icy roads without spikes—the inventors, after arriving at the previously described conclusions, propose to produce very finely distributed water receptacles in the tread which are able to rapidly receive the slightest quantities of water. Each of the aforementioned sinks represents such a water receptacle. Since the quantity of water to be received is small and the number of sinks is—in order to realize extremely short discharge paths—relatively high, the dimensions of each sink can be extremely small, namely so small that they are barely recognizable on the scale illustrated in FIG. 1 . These sinks preferably consist of a mere incision widening in the region of each incision stagger EV."
http://www.freepatentsonline.com/5181976.html"...This means that tangential forces, e.g., propulsive or brake forces, result in an increased tilting of the pad sections that are separated from one another by the incisions. Although this slightly improves the grip on snow-covered roads, the coefficient of friction on icy roads which is particularly critical in situations of this type significantly deteriorates because the aforementioned tilting concentrates almost the entire surface pressure on the very small edge surfaces. In other words, the reduced flexural strength eliminates the advantage of a reduced compressive rigidity in the pad center with respect to the most critical aspect of a winter tire, namely the grip on icy roads."
"...The numerous small sinks S at the staggers EV of the incisions E improve the microdrainage from the incisions. This improves the discharge of melt water from the ground contact surface. In contrast to wet roads on which significantly larger quantities of water are introduced into the contact area from the contact area inlet and, as far as possible, discharge in the front third of the contact area, a thin water film is only produced in the contact area itself when driving on ice due to melting. "
"...The thusly created water quantity naturally depends on the ice temperature; warm ice produces relatively large quantities of melt water. This is the reason why it is particularly difficult to drive on roads covered with warm ice.
Although the water quantities in case of warm ice are smaller than those on wet roads, the decrease in grip is particularly significant because the ice is nearly smooth. This means that a very small quantity of water can cause a complete separation of the tread from the solid ground.
In order to improve the most difficult aspect of a winter tiregrip on icy roads without spikes—the inventors, after arriving at the previously described conclusions, propose to produce very finely distributed water receptacles in the tread which are able to rapidly receive the slightest quantities of water. Each of the aforementioned sinks represents such a water receptacle. Since the quantity of water to be received is small and the number of sinks is—in order to realize extremely short discharge paths—relatively high, the dimensions of each sink can be extremely small, namely so small that they are barely recognizable on the scale illustrated in FIG. 1 . These sinks preferably consist of a mere incision widening in the region of each incision stagger EV."
"When the tread rubber is made softer, the true ground contact area of the tread can be increased to enhance the performances on ice, but the rigidity of the blocks in the tread is reduced to degrade the cornering stability on snow."
11-20-2009, 04:30 AM
#12
AudiWorld Senior Member
Happy, you were on good track with earlier posts but this "freepatents" crap is weirdest poop I have ever seen, sounds like people with too much time and no idea how to drive / handle car on snow have desided to describe winter tire function to patent application.
I will skip freepatents crap but I want to get back to this topic a bit later once I get out from work and talk about normal driving, off-roading and how width affects there.
Cheers...
I will skip freepatents crap but I want to get back to this topic a bit later once I get out from work and talk about normal driving, off-roading and how width affects there.
Cheers...
11-20-2009, 06:39 AM
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Happy, you were on good track with earlier posts but this "freepatents" crap is weirdest poop I have ever seen, sounds like people with too much time and no idea how to drive / handle car on snow have desided to describe winter tire function to patent application.
I will skip freepatents crap but I want to get back to this topic a bit later once I get out from work and talk about normal driving, off-roading and how width affects there.
Cheers...
I will skip freepatents crap but I want to get back to this topic a bit later once I get out from work and talk about normal driving, off-roading and how width affects there.
Cheers...
Anyway, if you think about it, searching the patents is a great source of facts. These people actually invest dollars into research, and then dollars into the patent, and then they often become the product that you use. Basically, they've got some skin in the game on this issue.
I unfortunately turn to this because I have yet to see anything like Mythbusters test this (despite a request or two), or Car&Driver, Motortrend, TireRack, etc. ever testing the idea. The funny thing is, you'd think this would be tested by a company like TireRack (or really a tire manufacturer) because if it turns out to be true, they stand to profit from selling wider tires. After all, a 235 width vs. a 225 width tire is an extra $20. I know, because I just bought 235 width X-ice2's and I have my friends 225 X-ice2's in my garage for their A4. The tires are practically the same width. The only thing that changed was the 235 tire has a wider shoulder on it to make it a 235. I highly doubt the extra rubber costs the manufacturer an extra $20, so selling a wider tire should be more profitable for them.
I look forward to your after-work reply. Should I get a shield of some sort to protect me?
(P.S. TireRack is wrong, wrong, wrong. They said a 235/45/R17 tire would not match the OEM size on an A4 B8 with 18" wheels as well as a 235/50/R17. I went with the 235/45 anyway which I just received... My friend has 225/50/R17 tires, and they are just slightly less than 1" taller then the OEM tire. Can you imagine how much taller a 235/50 would have been!!! My 235/45/R17 X-ice2's with 45mm offset matches my OEM 245/40/R18's about as good as you can get.)
11-21-2009, 10:00 AM
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I registered just to answer this as well. lol
You get traction on the road by your rubber tires interlocking with the pores in the road.
In dry conditions, wider is better because you have more surface area of the tire interlocking with the road. The air is easily displaced or compressed so you can even use slicks.
When conditions get wet, wider still gives you more contact area (more rubber interlocking with the asphalt) but you have to start worrying about moving water around... both on the surface and in the pores of the road. First you need grooves in order to channel the water away.
Now, since water isn't quite as easy to displace as air, you'll need more surface pressure from the tires to displace it from the pores in the road. So it's likely that increasing widths would make it progressively harder to get good traction on the road but I don't think the effect is significant enough to influence tire choices for the non-F1 driver... In this case, tread pattern is probably waaay more important.
Things get complicated when you start dealing with snow and ice. I think the slushy condition is basically like the rain situation I mentioned... tread pattern is probably way more important than tire width.
Once the snow becomes packed, the game totally changes. You might have just ventured into the classical physical model, where friction doesn't depend on surface area. Now you need to either create ridges in the snow that your tires can hold onto or have studs to push into and interlock with the snow surface or else you'll just slide on top of it.
Going wider likely means less pressure to create some ridges in the surface or on each stud.... again, whether that limit is low enough to affect real world tire selections is beyond my knowledge.
You get traction on the road by your rubber tires interlocking with the pores in the road.
In dry conditions, wider is better because you have more surface area of the tire interlocking with the road. The air is easily displaced or compressed so you can even use slicks.
When conditions get wet, wider still gives you more contact area (more rubber interlocking with the asphalt) but you have to start worrying about moving water around... both on the surface and in the pores of the road. First you need grooves in order to channel the water away.
Now, since water isn't quite as easy to displace as air, you'll need more surface pressure from the tires to displace it from the pores in the road. So it's likely that increasing widths would make it progressively harder to get good traction on the road but I don't think the effect is significant enough to influence tire choices for the non-F1 driver... In this case, tread pattern is probably waaay more important.
Things get complicated when you start dealing with snow and ice. I think the slushy condition is basically like the rain situation I mentioned... tread pattern is probably way more important than tire width.
Once the snow becomes packed, the game totally changes. You might have just ventured into the classical physical model, where friction doesn't depend on surface area. Now you need to either create ridges in the snow that your tires can hold onto or have studs to push into and interlock with the snow surface or else you'll just slide on top of it.
Going wider likely means less pressure to create some ridges in the surface or on each stud.... again, whether that limit is low enough to affect real world tire selections is beyond my knowledge.
11-21-2009, 09:30 PM
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I found myself agreeing with much of your points in your post, with maybe a few minor points here and there. I do agree with you that for daily driving, I believe tread pattern will make a much greater difference on how a tire performs for us vs. what an F1 driver would require. In fact, part of my questioning this notion here is questioning just how much a wider or narrow width really effect things at all anyway?
Let's just say that a more narrow tire REALLY IS BETTER (not that I'm conceding this yet, just saying this to establish my next point.) So if it really is better, at what point does it make a difference? They say that it takes a 20% difference or change in something for the human eye to be able to notice it. I've seen a lot of people that have downsized from 235 tires to say 215's or 205's. Just how much of a difference could this really make? Could it possibly make a 20% difference? I would guess that a good ABS, ESP and torque vectoring system could make a bigger percent change in a given situation than dropping a tire width by 10 or 15 millimeters. I can say that I've seen this first hand (as a passenger) with a Buick Rainier in the snow. It had one of the worst, I'd even say dangerous, AWD systems I've ever encountered. The driver was showing me how bad by taking me around a corner to show how it first let's you fishtail off a turn if you gave it any gas at all because only the rear wheels were receiving the power. THEN, it engages the front wheels drives when it detects slip while completely dis-engaging the rear-wheel drives and it pulls you forward into the other lane, then swaps back to the rear wheels to re-fish-tale you the other direction. Basically, the Buick AWD system was stupid, even with winter tires, because it kept shifting the full power front and back as it detected slip. YIKES!!! Wide, narrow, whatever, the tires just didn't matter at that point because it was too late.
I digres...
You mention about traction in wet conditions, and seem to admit that even in wet conditions, wider is better with the issue that wider tires probably don't move the water out from under the tire fast enough to allow the rubber to contact the road. I completely agree with this. I think the key difference here though is that I don't believe it always has to be more pressure of the tire on the road surface in order to displace the water. If you review the patents I mentioned earlier, and you can even research this on the Internet and see video's of it, tire manufactures have been putting in sipes in the tires to actually suck up the water on the road surface to leave a drier spot for the rubber to come in contact with. In other words, there are two ways to displace water. The first is with pressure to try and shove it out of the way from under the tire so the rubber can be in contact with the road. The other option is to suck it off the road.
The interesting thing I see with the sipes and the information about them is that they serve two purposes. The first is to allow the tread block to fold over so it produces a biting edge on hard packed and deep snow. The second however is to provide a channel that the water gets sucked up in and then dispelled as the wheel rotates. Basically, it acts like a little pump. If you take a look at the latest Michelin X-Ice XI2's, you'll notice that the outer tread block has sipes in which two rows of the sipes are not longitudinal, but are actually cylindrical. They describe it that the cylindrical holes are "mini-pumps" to suck up the small quantity of water that forms when driving in the winter. Oddly enough, the new X-Ice's are garnering some of the highest scores in traction on ice of all tires. Part of the reason that Michelin went with cylindrical holes was to maintain the integrity of the tread block for cornering purposes. Every time you make those wonderful little longitudinal sipes in the tire, it reduces the rigidity of the tread block for cornering. That's why there are so many patents for this, and why we are seeing more tires with slits (or sipes) that have curvy, wavy and angular shapes to them. It is to maintain the strength of the tread block, but still provide the benefits that a sipe provides.
So, let's bring this back to F1 race drivers. As kleinbus indicated in a previous post, a F1 car utilize a thinner tire for wets. That makes sense, as they really can't get away with sipes to suck up the water. If they used sipes, the tread blocks would never have the rigidity necessary for the G's they pull in the wet, and the tire would most likely over heat as the blocks were constantly moving. So, their only solution is to go narrow and try to "push" the water out of the way. Contrast this to daily driving. We're not pulling the type of G's they are, so we can get away with softer tread blocks that suck up the water and discharge it.
Here's another thing I find interesting. All of the patents indicate that a larger contact area is good for ice, but large spacing between the tread blocks is better for deep snow. I COMPLETELY agree with this. The goofy thing is, if we all ran wider tires, then the tire designers could have more liberty in creating a tread pattern that had more spacing between the tread blocks for deep snow, yet still had the contact area of what everyone is running for narrow tires currently. In other words, a tire designer could design a tread on a 245 tire that had lots of spacing for the deep snow, yet physically had the contact area of a 205 tire. If they tried to do the same thing with a 205 tire, they would probably end up with the contact area of a 165 tire.
I'll make one last comment about the tire width before I retire for the night. I used to run a Dunlop WinterSport M3. This tire has some pretty wide spacing between the tread blocks. Last year I ran Nokian R's, in a wider width, which had a fair amount of spacing between the tread blocks, but nothing like the Dunlops, and about twice as many sipes. They were better tires for sure than what the Dunlops were, yet they had a larger contact area in two regards. 1st, they were wider, 2nd, they had less space between the tread blocks which means more rubber on the roads. After picking up my new A4, I was forced to purchase new wheels, so I purchased new tires as well, and this time I picked up the X-Ice XI2's because all the reviews (even in Europe!) are indicating these are equal to the Nokian R's, yet they are more readily available and cheaper. I can tell you that these tires again have even less space between the tread blocks than what the Nokian's did, which ultimately means an even larger contact patch. The number of sipes looks to be about the same. So, long story short, I find it interesting that the top-scoring tire amongst all the manufacturers appears to have developed a tire that has some of the least amount of space between the tread blocks, aka, a larger contact area. Coincidence?
11-21-2009, 10:42 PM
#16
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It seems there's a general misunderstanding about how objects move through snow. I ski, snowmobile, offroad, and live where there is 300" of snow per year.
There are basically too kinds of snow, packed and loose and how you move through the two is very different. With both skiing and snowmobiling the you need an edge to bite on packed snow and ice. On skis you lean the ski over and bite with the blade edge. Ice skating is the same thing. Snowmobiles have skags on the bottoms of the skis. These bite into the surface and that's how you get traction.
As snow gets deeper and looser the edge bite does less. On skis and snowmobiles you bank through the powder. Your compressing and rebounding off the snow, pushing snow into snow. That's how you steer. On snowmobiles the track has little to do with steering, but rather propulsion. The track simultaneously compresses and displaces snow. The deeper and looser the snow gets the more you have to rely on displacement and the less on bite and compression. In deep powder you need a long track with large lugs to throw more snow. With a long track you float better and propel better in loose snow. But you don't want too wide a track or you compromise banking and steering.
Car tires don't have much in the way of edges or skags and they don't bank in powder. So no wonder they perform terribly in snow, compared to snowmobiles and skis.
The advantage to a skinny tire in snow doesn't come from getting down to the pavement, but rather getting below the surface of the snow enough to push on the snow, again compressing and rebounding. The deeper you are in the snow, the more the snow you have to displace to slide sideways and skinny tires get deeper in the snow than fat tires. And this has been my personal experience running both styles of tires. Tires that float on top of the snow are harder to steer.
That problem can, however, be offset with a deep open lug. In snow and sand in a car if you try to side hill, that is angle up a slope, the car will walk downhill. If you want to climb a hill, the thing to do is point it straight up, run big lug tires, and plenty of horsepower. You want to displace and dig simultaneously. In that case a fat tire with a big lug will do better than a skinny tire, more propulsion, less steering.
On the road, however, steering is the problem, not propulsion, and the skinnier tire is going to steer better in deep snow. On packed snow and ice, it's all about bite and friction. A large fat tire with an aggressive tread will do well on packed snow, but horribly on solid ice because rubber can't bit into the ice. On ice you need bite or friction. If you can't get bite then you have to fall back on friction. In the latter case, more surface area is helpful.
The best all around tire for snow and ice is going to be relatively narrow and have a tread with sharp corners. For deeper snow a narrower tire will keep a truck from walking sideways on an angled slope, but won't do as well paddling up hill.
Chains improve handling in almost every winter driving situation by biting into hard surfaces and displacing more snow.
There are basically too kinds of snow, packed and loose and how you move through the two is very different. With both skiing and snowmobiling the you need an edge to bite on packed snow and ice. On skis you lean the ski over and bite with the blade edge. Ice skating is the same thing. Snowmobiles have skags on the bottoms of the skis. These bite into the surface and that's how you get traction.
As snow gets deeper and looser the edge bite does less. On skis and snowmobiles you bank through the powder. Your compressing and rebounding off the snow, pushing snow into snow. That's how you steer. On snowmobiles the track has little to do with steering, but rather propulsion. The track simultaneously compresses and displaces snow. The deeper and looser the snow gets the more you have to rely on displacement and the less on bite and compression. In deep powder you need a long track with large lugs to throw more snow. With a long track you float better and propel better in loose snow. But you don't want too wide a track or you compromise banking and steering.
Car tires don't have much in the way of edges or skags and they don't bank in powder. So no wonder they perform terribly in snow, compared to snowmobiles and skis.
The advantage to a skinny tire in snow doesn't come from getting down to the pavement, but rather getting below the surface of the snow enough to push on the snow, again compressing and rebounding. The deeper you are in the snow, the more the snow you have to displace to slide sideways and skinny tires get deeper in the snow than fat tires. And this has been my personal experience running both styles of tires. Tires that float on top of the snow are harder to steer.
That problem can, however, be offset with a deep open lug. In snow and sand in a car if you try to side hill, that is angle up a slope, the car will walk downhill. If you want to climb a hill, the thing to do is point it straight up, run big lug tires, and plenty of horsepower. You want to displace and dig simultaneously. In that case a fat tire with a big lug will do better than a skinny tire, more propulsion, less steering.
On the road, however, steering is the problem, not propulsion, and the skinnier tire is going to steer better in deep snow. On packed snow and ice, it's all about bite and friction. A large fat tire with an aggressive tread will do well on packed snow, but horribly on solid ice because rubber can't bit into the ice. On ice you need bite or friction. If you can't get bite then you have to fall back on friction. In the latter case, more surface area is helpful.
The best all around tire for snow and ice is going to be relatively narrow and have a tread with sharp corners. For deeper snow a narrower tire will keep a truck from walking sideways on an angled slope, but won't do as well paddling up hill.
Chains improve handling in almost every winter driving situation by biting into hard surfaces and displacing more snow.
11-22-2009, 07:40 PM
#17
AudiWorld Senior Member
The "lot of horse power" does not work with snow. It just sunks you right away with snow off-roading and you should know that if you really get that much snow and your hobby is off-roading.
I went side ways with relatively small tires on sand dunes and well, I guess it is the real experience than just talk that kept me going...
.....There are basically too kinds of snow, packed and loose and how you move through the two is very different. With both skiing and snowmobiling the you need an edge to bite on packed snow and ice. On skis you lean the ski over and bite with the blade edge. Ice skating is the same thing. Snowmobiles have skags on the bottoms of the skis. These bite into the surface and that's how you get traction........
After skiing since little boy, the skii edge bites to ice under the snow layer but on powder, it is the flat bottom that gives the control as there is nothing hard for edge to bite on.
The skiidoo (snowmobile) track does displace snow only at hard acceleration as it throws snow stripe behind the machine. On normal travel it only compresses...
Few winters ago back in Finland when I had one of the few real 4x4 cars, stock Mercedes G diesel stick with all 3 mechanical differential locks (front-middle-rear). One weekend I went to play around with it on no-winter-maintenance forrest road that I knew had surface at summer time but at winter, snow was on my hips (I'm 5'9") as I went there walking and sunk. Car had brand new Bf G all terrain 31-11.5-R16 tires so I engaged low range and the 1st gear, locked all 3 locks and gave some gas to climb over the bank from main road. First few car lenghts went fine but then wheels started digging and sinking the car, I lifted my feet off from gas and engine on idle kept me going on walking speed and it climbed up again. Few car lenghts later I gently pressed gas to try to go faster and same spinning - digging happened again, this time so bad that I got stuck and I had to shovel snow away from under the car to get it back on its wheels.
So lets just separate the off-roading from this topic as it would get this so compicated that we would probably end up flaming back and forth. On off-roading wider tire helps a lot on sand and snow, but those very same wide tires gave me hairy moments on same road where I wrove my Passat with unstudded tires without any issues. With another car with studded tires made me feel there was no ice at all...
Happy, no shields needed as to me, this is free world, one could like green and other yellow and one is not better than other, it is just color for heavens sake...
I'm design engineer for vehicle industry (18 wheelers) so I know patent applications and I'm familiar with wording. I just can't help myself feeling freepatentsonline is mostly about the folks who are after easy money and royalties as there is too many same ideas just described different ways.
Ok lets go back to the original topic and the tires...
First of all, someone have to define what is narrow and wide tire. Is narrow 195 and wide 235 or even 255?
You don't find much traction difference between 195 and 205 as the width difference is so small, but if you throw 255 unstudded tires to Passat or A4, you will get slush slide earlier at slower speeds than with 195 or 205 as sluch is even worse than normal hydroplanning when the ice-water mixture does not get out from thread as easilly as pure water.
I'm not sure how much there is traction difference between 195 and 235 on clean snow surface but on powder the wider starts floating earlier than narrower.
My winter tire experience is from studded and unstudded real winter tires, like Nokian Hakkapeliitta, Bridgestone Blizzak and Michelin X-Ice. Sizes from 195 to 205 on MB C serie, Passat, Passat Variant, Volvo S40, Mitzu Galant, Subaru Lagacy and 235 on Transporter Syncro. The 4x4's I had is another story so I don't include those. Also I have tried other winter tire brands and learnt only few knows how to make real winter tires.
Dry ice and wet ice, go with studded tires as there is no other tire giving you such traction. (I know it is not allowed in some states / countries)
I don't know how this is called here in States, but back in Finland few times in winter when temperature below -10C (14F), it starts raining water and once the drop hits a surface, it freezes immediately (ice storm?), anyways, I was on side road, blasting all heat to windshield to keep ice melting and the darn road was like ice hockey ring so I with unstudded tires (why did I take that car that day?), had to drive on curb with speed about 5 mph so if I would slide somewhere, at least it would not cause bad damage. I tried to go to my own lane and car started to slide right away so I returned to curb where I had some traction. Took 30 mins to drive part that normally took less than 10 mins.
Last winter, here in Kansas we had few days snow, first day the highway next to us became ice hockey ring, normally I fly by 75mph but that day when we were coming back home with our Tiguan with Blizzaks, I noticed how light the steering was and how "glittery/shiny" the road was, so as no one was behind us, I told wife to hold on and on straight part I gently started pressing brake, barely touched the pedal when I heard ABS system sound so I knew it was way too slippery, without pressing the gas I slowed down from 65 to 40. Few cars passed me like crazy and few mins later we started counting the cars and trucks in ditches and on side of the road. Well we got home safe and sound....
Tiguan was with 235 and current Q5 haves 235 winter set so do I feel 225 or 215 would give me advantage? Both cars have 235 summer tires so 205 or even 195 would look so stupid "bicycle" tire that would be no go to me. Anyways, the small advantage narrower could have, if such advantage exists, I can always compensate by slowing down...
Last edited by kleinbus; 11-22-2009 at 07:58 PM.
11-23-2009, 07:22 AM
#18
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This thread is very relevant to me... About to purchase winter set for my '10 a4 quattro. Half of my winter driving is around NY/NJ and not a big deal. The other half is what matters, driving to vermont/upstate NY during/after snow dumps. This means snowy or more frequently slushy interstates with stressed traffic. I've had dunlop winter sport m3 or 3d's on different bmws now for the five seasons.
The ideal winter size for the b8 a4 is 225/50-17. Narrower is plain silly for me, as are non-performance super soft winters. I prefer the 3d's (smoother on highway, slightly better on snow) but no one has them in that size. They also had a fault/recall in that size a year ago, so I won't get them used without checking DOT numbers. The m3's are available in that size, but I have a less favorable memory of them. The 3d's exist in 245/45-17, which will also fit my OEM 17" winter wheel set, but then is 245 too wide for snow tires?
What will it be? The tire that I like better in 245 or the tire that I like slightly less 225?
The ideal winter size for the b8 a4 is 225/50-17. Narrower is plain silly for me, as are non-performance super soft winters. I prefer the 3d's (smoother on highway, slightly better on snow) but no one has them in that size. They also had a fault/recall in that size a year ago, so I won't get them used without checking DOT numbers. The m3's are available in that size, but I have a less favorable memory of them. The 3d's exist in 245/45-17, which will also fit my OEM 17" winter wheel set, but then is 245 too wide for snow tires?
What will it be? The tire that I like better in 245 or the tire that I like slightly less 225?
11-23-2009, 08:54 AM
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Horsepower absolutely matters at the extreme end of wheeling. Normal car, normal tires you have no propulsion, you just bury it. Go to youtube and search snow wheeling, you will see that HP clearly matters. That's true of 4wheeling and snowmobiling. Higher HP snowmobiles get stuck less. The compromise, however, is weight. With snowmobiles and trucks there's a happy medium, optimal power to weight ratio. What that is, is debatable. Slednecks want to add power without adding weight.
Regarding skiing think about what the flat of the ski is doing, it's pushing and compressing the snow. There's lots of banking and leaning and balancing of pressure against snow working in conjunction with gravity. Your constantly pushing against the snow to control speed and direction.
Similarly there's an equilibrium point for tire width. If you don't have a big lug, or anything to bite, your going to do better being a little under the surface of the snow than floating on top of it. If the tire is down in the snow you're using the sides of the tire as well, particularly if you have something on the sidewall that can bite and dig. In that case you actually have more surface area in contact with a surface that's not exactly flat. If you're on top of the snow, with out much lug to bite, you're going to push across the snow very easily in a turn. If you get down in the snow a bit then you have snow pushing against the sidewall resisting sliding in a turn.
So there's an equilibrium point for the width of the tire. too skinny and you get down in the snow, but you have little surface area. Too wide and you slide over the top. However, if you have some kind of lug, you can go really wide and go on top, and grab, think snowcat. But that's not practical on a car.
On a light pu, a narrower tire with an aggresive lug and side bite, for example BFG MT 75-85 will do better on snowy roads than a BFG AT 33x12.5 wide high floating tire, If you want to go wide you have to compensate with a lot of lug to bite and propel.
Sand and snow wheelers use wide tires and large paddles/lugs. They want to float and propel. The more horsepower you have the more paddle you can run, provided your axles can handle the stresses. If you can float and you can paddle, you can move faster over the snow or sand with more HP, without just digging in and burying.
Regarding skiing think about what the flat of the ski is doing, it's pushing and compressing the snow. There's lots of banking and leaning and balancing of pressure against snow working in conjunction with gravity. Your constantly pushing against the snow to control speed and direction.
Similarly there's an equilibrium point for tire width. If you don't have a big lug, or anything to bite, your going to do better being a little under the surface of the snow than floating on top of it. If the tire is down in the snow you're using the sides of the tire as well, particularly if you have something on the sidewall that can bite and dig. In that case you actually have more surface area in contact with a surface that's not exactly flat. If you're on top of the snow, with out much lug to bite, you're going to push across the snow very easily in a turn. If you get down in the snow a bit then you have snow pushing against the sidewall resisting sliding in a turn.
So there's an equilibrium point for the width of the tire. too skinny and you get down in the snow, but you have little surface area. Too wide and you slide over the top. However, if you have some kind of lug, you can go really wide and go on top, and grab, think snowcat. But that's not practical on a car.
On a light pu, a narrower tire with an aggresive lug and side bite, for example BFG MT 75-85 will do better on snowy roads than a BFG AT 33x12.5 wide high floating tire, If you want to go wide you have to compensate with a lot of lug to bite and propel.
Sand and snow wheelers use wide tires and large paddles/lugs. They want to float and propel. The more horsepower you have the more paddle you can run, provided your axles can handle the stresses. If you can float and you can paddle, you can move faster over the snow or sand with more HP, without just digging in and burying.
11-23-2009, 09:24 PM
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TIRE UPDATE
Got some Michelin X-Ice 2 195/60 15s put on my Saab 9-3 a couple of days ago. No snow yet here in Michigan but they drive great on dry pavement so far. They are a little squishy in the turns which is to be expected. Highway speeds are great, just a faint high pitched noise. Will update with snow and ice reports through the season.