AWD with Summer tires vs 2WD with Winter Tires
12-17-2014, 05:40 AM
#1
AWD with Summer tires vs 2WD with Winter Tires
It's the tire compound that matters, not so much the size of the wheel/tire. Be sure to watch the Video.
Here's Proof All-Wheel Drive Is Useless In The Snow Without Proper Tires
Here's Proof All-Wheel Drive Is Useless In The Snow Without Proper Tires
12-17-2014, 07:29 AM
#2
I am not an expert but do have a significant amount of experience driving in places that have a lot of snow and ice. My take is that tires are very important and AWD is very important. As more and more manufacturers offer digital-controlled traction control, the extra edge provided by AWD seems to be diminishing.
I do feel that AWD with winter tries will be better than a FWD car with the same tires. For about 10 years I had a weekend home in the Catskill Mountains at a 3,100 ft. elevation (not much elsewhere in the US, but pretty high up for New York State). I was on a private road (not maintained by the local Town) with a pretty steep grade, so much so, that the Town would not take over maintenance because it exceeded the grade limit. Oil trucks, etc. declared no deliveries from November 1 to April 1 because of the difficulty in getting up the road. One time a FedEx truck got stuck and slid sideways into the drainage ditch for several hours until it was rescued. After that they never tried to deliver in bad weather.
Point is, for a while I had two cars during a certain time frame (a 1998 Isuzu Trooper with part-time 4-wheel drive and a 2002 4-cylinder Altima). The Trooper had 16” non-winter SUV tires and on the Altima for the cold season I put on Bridgestone Blizzak’s. Generally speaking the Altima could handle the winter conditions pretty well with the Blizzak’s , but there were occasional times I had to park at the bottom and walk almost half a mile up the hill on foot. The thing that helped was some spray-on “liquid tire chain” I bought at an auto parts store. That stuff didn’t last long, but usually got me up the hill.
The Trooper on the other hand never got stuck, not once. The extra ground clearance helped, when the snow was deep (since the Town did not maintain the road we had to rely on the homeowners deciding as a group after each snowfall whether to pay to have the road cleared – what a pain). The one thing I would say with certainty is that the Altima with the winter tries was more stable on slick roads at normal speeds than the Trooper was. The SUV’s higher center of gravity doesn’t help when you’re going 50 mph on a slick road, AWD or not.
I think a better situation is AWD with winter tries. Also, the winter tries should be narrower than most folks like for their year-rounds these days. On my Altima I did get a narrower, higher wall winter tire and black painted skinny wheels. A wide tire tends to ride up on the snow and (given the same vehicle weight) they exert a lower lb./sq. inch than do a narrower tire. Higher lb./sq. inch will help with traction and breaking through crusty ice ridges.
Regarding the video I have no idea if the drivers have equal winter driving skills - that is important. The last point I would make about the video is that it is a slight uphill grade. The rear wheel drive BMW gets the advantage on an uphill of the engine weight shifting back to the rear drive wheels, improving traction. With a FWD car or with the Forester, on an uphill the weight shifting to the rear wheels does not help so much in improving traction. With the Forester there was likely very little weight on the fronts on the uphill, which is likely why it started fishtailing. With my FWD Altima I found sometimes that backing up enabled the car to get up the hill as the weight then did shift to the front drive wheels. A half mile long, twisting dirt road is a bitch to maneuver in reverse, so I didn’t do that very frequently - only as an absolute necessity.
I do feel that AWD with winter tries will be better than a FWD car with the same tires. For about 10 years I had a weekend home in the Catskill Mountains at a 3,100 ft. elevation (not much elsewhere in the US, but pretty high up for New York State). I was on a private road (not maintained by the local Town) with a pretty steep grade, so much so, that the Town would not take over maintenance because it exceeded the grade limit. Oil trucks, etc. declared no deliveries from November 1 to April 1 because of the difficulty in getting up the road. One time a FedEx truck got stuck and slid sideways into the drainage ditch for several hours until it was rescued. After that they never tried to deliver in bad weather.
Point is, for a while I had two cars during a certain time frame (a 1998 Isuzu Trooper with part-time 4-wheel drive and a 2002 4-cylinder Altima). The Trooper had 16” non-winter SUV tires and on the Altima for the cold season I put on Bridgestone Blizzak’s. Generally speaking the Altima could handle the winter conditions pretty well with the Blizzak’s , but there were occasional times I had to park at the bottom and walk almost half a mile up the hill on foot. The thing that helped was some spray-on “liquid tire chain” I bought at an auto parts store. That stuff didn’t last long, but usually got me up the hill.
The Trooper on the other hand never got stuck, not once. The extra ground clearance helped, when the snow was deep (since the Town did not maintain the road we had to rely on the homeowners deciding as a group after each snowfall whether to pay to have the road cleared – what a pain). The one thing I would say with certainty is that the Altima with the winter tries was more stable on slick roads at normal speeds than the Trooper was. The SUV’s higher center of gravity doesn’t help when you’re going 50 mph on a slick road, AWD or not.
I think a better situation is AWD with winter tries. Also, the winter tries should be narrower than most folks like for their year-rounds these days. On my Altima I did get a narrower, higher wall winter tire and black painted skinny wheels. A wide tire tends to ride up on the snow and (given the same vehicle weight) they exert a lower lb./sq. inch than do a narrower tire. Higher lb./sq. inch will help with traction and breaking through crusty ice ridges.
Regarding the video I have no idea if the drivers have equal winter driving skills - that is important. The last point I would make about the video is that it is a slight uphill grade. The rear wheel drive BMW gets the advantage on an uphill of the engine weight shifting back to the rear drive wheels, improving traction. With a FWD car or with the Forester, on an uphill the weight shifting to the rear wheels does not help so much in improving traction. With the Forester there was likely very little weight on the fronts on the uphill, which is likely why it started fishtailing. With my FWD Altima I found sometimes that backing up enabled the car to get up the hill as the weight then did shift to the front drive wheels. A half mile long, twisting dirt road is a bitch to maneuver in reverse, so I didn’t do that very frequently - only as an absolute necessity.
Last edited by irenesbob; 12-17-2014 at 07:32 AM.
12-18-2014, 09:57 AM
#3
AudiWorld Senior Member
On my Altima I did get a narrower, higher wall winter tire and black painted skinny wheels. A wide tire tends to ride up on the snow and (given the same vehicle weight) they exert a lower lb./sq. inch than do a narrower tire. Higher lb./sq. inch will help with traction and breaking through crusty ice ridges.
12-18-2014, 04:23 PM
#4
I'm not sure I totally agree. Going from one size of lower profile tire to another size of higher profile tire may not result in the exact same contact patch area, but your point regarding the shape of the patch is spot on. In my case I went to a much skinner, higher tire for winter and it had steel wheels vs. the alloy year-rounds (more unsprung weight) so I think my point may be valid-ish (he, he) in my example. Certainly the higher sidewalls are a big winter advantage. I gotta admit that I was actually a bit confused when I made my earlier post and was thinking of two cars with the same size tire (as often happens) and that the heavier one may be better at crunching through the white stuff.
12-18-2014, 07:15 PM
#5
AudiWorld Senior Member
I'm not sure I totally agree. Going from one size of lower profile tire to another size of higher profile tire may not result in the exact same contact patch area, but your point regarding the shape of the patch is spot on. In my case I went to a much skinner, higher tire for winter and it had steel wheels vs. the alloy year-rounds (more unsprung weight) so I think my point may be valid-ish (he, he) in my example. Certainly the higher sidewalls are a big winter advantage. I gotta admit that I was actually a bit confused when I made my earlier post and was thinking of two cars with the same size tire (as often happens) and that the heavier one may be better at crunching through the white stuff.
For the reasons noted above, a heavier car on the same-sized tire (and using the same tire pressures) will create a bigger contact patch, which might negate any "crunching" advantage.
* Again, there is some variability due to tire construction, type and sidewall height/stiffness, but the concept remains intact.
12-18-2014, 10:12 PM
#6
The following quote is from Tire Contact Patch | Lowering Pressure Gain Traction
“According to the Avon data and these calculations, the contact patch pressure not only does not remain close to constant, it never even approaches that of the air pressure in the tire. Granted, sidewall deflection is not included here so in reality the contact patch pressures are likely to be higher than what is shown, possibly significantly. But what is immediately obvious is that doubling the load does not double the contact patch area. I.e., the contact patch pressure does not remain constant.”
Take a look at the report and tell me (I am not an engineer nor am I technically skilled in this area) what it says to either support or refute your statements, and for that matter, mine.
I am not trying to argue or fight with you, but I simply cannot believe that a simple equation such as you presented: 1,000 lbs divided by 40 PSI tire pressure equals 25 sq. in. of contact patch area. It is my experience that road tires with really low pressure can lose contact with the road surface at the center of the tread, making it hard to believe the contact area always increases at lower tire pressure. Flotation type sand tires used on dune buggies, for example, are obviously different.
“According to the Avon data and these calculations, the contact patch pressure not only does not remain close to constant, it never even approaches that of the air pressure in the tire. Granted, sidewall deflection is not included here so in reality the contact patch pressures are likely to be higher than what is shown, possibly significantly. But what is immediately obvious is that doubling the load does not double the contact patch area. I.e., the contact patch pressure does not remain constant.”
Take a look at the report and tell me (I am not an engineer nor am I technically skilled in this area) what it says to either support or refute your statements, and for that matter, mine.
I am not trying to argue or fight with you, but I simply cannot believe that a simple equation such as you presented: 1,000 lbs divided by 40 PSI tire pressure equals 25 sq. in. of contact patch area. It is my experience that road tires with really low pressure can lose contact with the road surface at the center of the tread, making it hard to believe the contact area always increases at lower tire pressure. Flotation type sand tires used on dune buggies, for example, are obviously different.
12-19-2014, 07:35 AM
#7
AudiWorld Senior Member
I guess I should not have simplified (although I touched on the issues involved with my asterisk). There is no misleading data in that article, although it should be taken with a grain of salt because it's looking at race tires with construction and design parameters that are significantly different from even a high-performance street tire. Yes, because tires are not balloons and have a semi-rigid shell, the simplistic formula I presented will almost never be correct.
What I was trying to negate is the misperception that a wider tire puts "more meat on the ground". Per the data in the article, at mid-level tire pressures, there is very little contact patch area difference between the skinny front tires and the much wider ones in the rear. At less "normal" pressures, this relationship varies, but this is due to decisions made by Avon tire engineers to optimize the tire for its intended purpose.
My summer fun car is a 350 whp Miata. Given that it weighs less than 2,500 lbs, you would think that putting all that power to the ground would be problematic (and you'd be right). However, for comfort on the street I run 195/50-R15 tires on all four corners and, despite protestations from the "wider is better" camp, I can lay down the power almost as well as with my 225/45-R15 race-compound tires (any difference in straight-line traction is due to the stickier compound on the latter and not due to them being wider). In fact, for straight-line traction, a long contact patch is superior (a wider contact patch, by contrast, supports cornering loads better).
The absolute numbers are less important than the concepts. Coles Notes: All else being equal (which they never are), a wider tire provides no bigger a contact patch than a narrow tire. All else being equal, increasing tire pressure decreases the size of the contact patch, and vice versa. All else being equal, adding more weight (static or dynamic) increases the size of the contact patch, and vice versa. Finally, for all the reasons listed in that article, these changes are not proportional.
What I was trying to negate is the misperception that a wider tire puts "more meat on the ground". Per the data in the article, at mid-level tire pressures, there is very little contact patch area difference between the skinny front tires and the much wider ones in the rear. At less "normal" pressures, this relationship varies, but this is due to decisions made by Avon tire engineers to optimize the tire for its intended purpose.
My summer fun car is a 350 whp Miata. Given that it weighs less than 2,500 lbs, you would think that putting all that power to the ground would be problematic (and you'd be right). However, for comfort on the street I run 195/50-R15 tires on all four corners and, despite protestations from the "wider is better" camp, I can lay down the power almost as well as with my 225/45-R15 race-compound tires (any difference in straight-line traction is due to the stickier compound on the latter and not due to them being wider). In fact, for straight-line traction, a long contact patch is superior (a wider contact patch, by contrast, supports cornering loads better).
The absolute numbers are less important than the concepts. Coles Notes: All else being equal (which they never are), a wider tire provides no bigger a contact patch than a narrow tire. All else being equal, increasing tire pressure decreases the size of the contact patch, and vice versa. All else being equal, adding more weight (static or dynamic) increases the size of the contact patch, and vice versa. Finally, for all the reasons listed in that article, these changes are not proportional.
Last edited by DeerHunter; 12-19-2014 at 07:38 AM.
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12-19-2014, 12:08 PM
#9
...Coles Notes:[/B] All else being equal (which they never are), a wider tire provides no bigger a contact patch than a narrow tire. All else being equal, increasing tire pressure decreases the size of the contact patch, and vice versa. All else being equal, adding more weight (static or dynamic) increases the size of the contact patch, and vice versa. Finally, for all the reasons listed in that article, these changes are not proportional.
In all my disagreeing with you, I forgot that over time as folks moved toward ever wider, lower profile tires one of the principal reasons was to reduce sidewall flex.
12-20-2014, 07:41 AM
#10
We got our first significant snow at Lake Tahoe yesterday. I went up a 1/4mile road with 7% grade near my home with snow as shown in the picture. Tires are Blizzak LM60 Snow Tires, car is 2WD rear. Minor amount of rear-wheel slip getting up to 25mph, but no problem making it up the hill.