I Took My 8 Out in The Snow With the Stock Tires for the 1st Time...
#1
*Update*SONOFABITCH! TPMS & non-oem rims! 8 and snow w/stock tires for 1st time
...and I almost had a freaking heart attack.
I'm really hoping that getting a set of 17" wheels with some quality snow tires DRAMATICALLY improves traction, control and braking, otherwise, I'm just going to have to buy a winter beater.
There's no other way around it.
***Update - Most 17" after market rims that I had hoped to mount my winter tires on reportedly screw with the Mazda Tire Pressure Monitoring System!!!
![Mad](https://www.rx8club.com/images/smilies/mad.gif)
I'm really hoping that getting a set of 17" wheels with some quality snow tires DRAMATICALLY improves traction, control and braking, otherwise, I'm just going to have to buy a winter beater.
There's no other way around it.
***Update - Most 17" after market rims that I had hoped to mount my winter tires on reportedly screw with the Mazda Tire Pressure Monitoring System!!!
![Banghead](https://www.rx8club.com/images/smilies/banghead.gif)
Last edited by RotoRocket; 12-06-2005 at 12:48 PM.
#2
RX8 and a Truk....
do you have DSC? Mine goes okay - probably as well as my wife's F150 (when it's not in 4x4). I have the Dunlops - which tires do you have? How 'bad' was your snow?
#3
Originally Posted by dmp
do you have DSC? Mine goes okay - probably as well as my wife's F150 (when it's not in 4x4). I have the Dunlops - which tires do you have? How 'bad' was your snow?
The ABS is just plain harsh in peddle feedback. Very disturbing.
The DSC kicked in when the rear end broke free, as the dash light indicated.
The snow was about an inch, mixed with a little ice.
I was on the stock Potenzas. Therein lies the problem, I certainly hope.
My other vehicle right now is a Jeep 4x4, but it comes off lease in two months.
If the 8 doesn't do radically better on a good set of Blizzaks, Winter Dunlops, or Winter Hankooks, it'll be garaged in the winter, because driving it in those conditions is too damn nerve wracking.
#4
RX8 and a Truk....
Originally Posted by RotoRocket
Yes. I have a 6 Speed M/T Sport, with DSC and ABS.
The ABS is just plain harsh in peddle feedback. Very disturbing.
The DSC kicked in when the rear end broke free, as the dash light indicated.
The snow was about an inch, mixed with a little ice.
I was on the stock Potenzas. Therein lies the problem, I certainly hope.
My other vehicle right now is a Jeep 4x4, but it comes off lease in two months.
If the 8 doesn't do radically better on a good set of Blizzaks, Winter Dunlops, or Winter Hankooks, it'll be garaged in the winter, because driving it in those conditions is too damn nerve wracking.
The ABS is just plain harsh in peddle feedback. Very disturbing.
The DSC kicked in when the rear end broke free, as the dash light indicated.
The snow was about an inch, mixed with a little ice.
I was on the stock Potenzas. Therein lies the problem, I certainly hope.
My other vehicle right now is a Jeep 4x4, but it comes off lease in two months.
If the 8 doesn't do radically better on a good set of Blizzaks, Winter Dunlops, or Winter Hankooks, it'll be garaged in the winter, because driving it in those conditions is too damn nerve wracking.
The key is, adopt the attitude: "So what if the ABS kicks on, and the Lights flash...the car is still moving and stopping, right??" :D
The ABS feeling-clunking, etc, is typical of all ABS systems I've driven. - Here's what I was driving just fine on, a couple days ago...with the DSC switched off. :D
https://www.rx8club.com/rx-8-multimedia-photo-gallery-6/i-love-snow-oem-tires-who-needs-turbo-77506/
#5
Originally Posted by dmp
The key is, adopt the attitude: "So what if the ABS kicks on, and the Lights flash...the car is still moving and stopping, right??" :D
The ABS feeling-clunking, etc, is typical of all ABS systems I've driven. - Here's what I was driving just fine on, a couple days ago...with the DSC switched off. :D
https://www.rx8club.com/showthread.php?t=77506
The ABS feeling-clunking, etc, is typical of all ABS systems I've driven. - Here's what I was driving just fine on, a couple days ago...with the DSC switched off. :D
https://www.rx8club.com/showthread.php?t=77506
I think I'm going to give some Hankook Icebears a shot, dmp.
The car was still moving and stopping, but not always when or where I wanted it to. I went about 4 miles in busy traffic before I simply lost my nerve and went home to grab the Jeep.
#6
Shock and Awe
The first year I bought my 8, I took it on a road trip from El Paso to Pittsburgh... in December. I remember having troubles in the snow, so I can feel your pain.
#7
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I live in Madison, Wisconsin and use the 8 as my everyday car, all year long.
I have been really happy the last two winters with my Dunlop Wintersport M3's mounted on 17" wheels. Check out Tirerack, they have some good packages.
I have been really happy the last two winters with my Dunlop Wintersport M3's mounted on 17" wheels. Check out Tirerack, they have some good packages.
#9
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Originally Posted by cleoent
Actually i've heard with decent snow tires the rx makes a good snow car.
#10
I did several searches on snow tires.
I'm torn between the Dunlop M3s and the Blizzaks.
I know it's actually typically cheaper to buy a 17" inch wheel package with snow tires, rather than try to stick larger tires on the existing 18" rims, and that you can avoid the TPMS problems by doing so, too.
I really am kind of bummed right now. I'm hoping that a good set of snow tires saves the additional expense (purchase cost, insurance, maintenance) of having to have a spare CAR for the winter.
Edit- I meant spare "car," and not spare "tire." lmao. Sorry everyone.
I'm torn between the Dunlop M3s and the Blizzaks.
I know it's actually typically cheaper to buy a 17" inch wheel package with snow tires, rather than try to stick larger tires on the existing 18" rims, and that you can avoid the TPMS problems by doing so, too.
I really am kind of bummed right now. I'm hoping that a good set of snow tires saves the additional expense (purchase cost, insurance, maintenance) of having to have a spare CAR for the winter.
Edit- I meant spare "car," and not spare "tire." lmao. Sorry everyone.
Last edited by RotoRocket; 12-02-2005 at 09:58 PM.
#11
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Originally Posted by RotoRocket
I did several searches on snow tires.
I'm torn between the Dunlop M3s and the Blizzaks.
I know it's actually typically cheaper to buy a 17" inch wheel package with snow tires, rather than try to stick larger tires on the existing 18" rims, and that you can avoid the TPMS problems by doing so, too.
I really am kind of bummed right now. I'm hoping that a good set of snow tires saves the additional expense (purchase cost, insurance, maintenance) of having to have a spare tire for the winter.
I'm torn between the Dunlop M3s and the Blizzaks.
I know it's actually typically cheaper to buy a 17" inch wheel package with snow tires, rather than try to stick larger tires on the existing 18" rims, and that you can avoid the TPMS problems by doing so, too.
I really am kind of bummed right now. I'm hoping that a good set of snow tires saves the additional expense (purchase cost, insurance, maintenance) of having to have a spare tire for the winter.
#12
snow
i also just taken mine out(with stock tires) for the first time in about 2" of snow.
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
#13
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Originally Posted by joeman
i also just taken mine out(with stock tires) for the first time in about 2" of snow.
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
#14
Purveyor of fine bass
We will get snow soon (this weekend). I will drive out on my brand new M3s and tell you how it is (ok, so I put about 700 miles on my m3s so far, so they are well broken in, but still pretty darn new).
I looked at the stock Dunlops... I don't know which ones you have, but I have the stock Dunlops (not Bridgestones). No way in hell are those tires usable in snow. They have no siping (little block cuts) to speak off... they have big, solid blocks, and they got pretty hard in cold temps. No siping means really poor ice traction, plus getting so hard in cold temps is like riding on hard plastic and not rubber. Dunlop calls them "Ultra High Performance Summer" tires, not even all-seasons.
So far, I get better dry traction in my snows (Dunlop M3s) at cold temps (30 deg) than my OEM tires.
Which Blizzaks are you looking at? The LM-22s? Go for the cheapest, if you are concerned about the price.
TPMS doesn't bug me: the light blinks. No beeps. I may put tape/sticker over it.
You want snow tires, and 17" package lets you go for a narrower tire. Narrower tire means better snow traction.
I looked at the stock Dunlops... I don't know which ones you have, but I have the stock Dunlops (not Bridgestones). No way in hell are those tires usable in snow. They have no siping (little block cuts) to speak off... they have big, solid blocks, and they got pretty hard in cold temps. No siping means really poor ice traction, plus getting so hard in cold temps is like riding on hard plastic and not rubber. Dunlop calls them "Ultra High Performance Summer" tires, not even all-seasons.
So far, I get better dry traction in my snows (Dunlop M3s) at cold temps (30 deg) than my OEM tires.
Which Blizzaks are you looking at? The LM-22s? Go for the cheapest, if you are concerned about the price.
TPMS doesn't bug me: the light blinks. No beeps. I may put tape/sticker over it.
You want snow tires, and 17" package lets you go for a narrower tire. Narrower tire means better snow traction.
#15
Bummed, but bring on OU!
Originally Posted by joeman
i also just taken mine out(with stock tires) for the first time in about 2" of snow.
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. it is not that it doesn't go in the snow, i can get it going eventually. it is i cannot get it to stop unless i put it in neutral. if i did not know this trick it would be is someones living room right now.
this car has just too many caveats. this site has been a god send of important info. i still like the car but is is not a plug and play auto. joe
snow tires
...
You cannot expect summer high performance tires to do anything in the snow. Don't bash the car when inadequate equipment is the problem. Fwiw, I did fine in an inch or 2 of slushy snow on my summer tires (BFG KDW2's), but I had to baby the throttle the whole way.
#16
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Last year I went without snow tires and got stuck\. This year I got Blizzaks and what a big difference, I actually like to go out and drive in the snow now. I put two 40 lb salt bags in the trunk and it seems to help give the backend more traction. I am now not afraid like I was last year to go out and tear it up. I have been passing trucks and suvs they all seem to be in the way now.
![Rock](https://www.rx8club.com/images/smilies/rock.gif)
#17
Originally Posted by Astral
We will get snow soon (this weekend). I will drive out on my brand new M3s and tell you how it is (ok, so I put about 700 miles on my m3s so far, so they are well broken in, but still pretty darn new).
I looked at the stock Dunlops... I don't know which ones you have, but I have the stock Dunlops (not Bridgestones). No way in hell are those tires usable in snow. They have no siping (little block cuts) to speak off... they have big, solid blocks, and they got pretty hard in cold temps. No siping means really poor ice traction, plus getting so hard in cold temps is like riding on hard plastic and not rubber. Dunlop calls them "Ultra High Performance Summer" tires, not even all-seasons.
So far, I get better dry traction in my snows (Dunlop M3s) at cold temps (30 deg) than my OEM tires.
Which Blizzaks are you looking at? The LM-22s? Go for the cheapest, if you are concerned about the price.
TPMS doesn't bug me: the light blinks. No beeps. I may put tape/sticker over it.
You want snow tires, and 17" package lets you go for a narrower tire. Narrower tire means better snow traction.
I looked at the stock Dunlops... I don't know which ones you have, but I have the stock Dunlops (not Bridgestones). No way in hell are those tires usable in snow. They have no siping (little block cuts) to speak off... they have big, solid blocks, and they got pretty hard in cold temps. No siping means really poor ice traction, plus getting so hard in cold temps is like riding on hard plastic and not rubber. Dunlop calls them "Ultra High Performance Summer" tires, not even all-seasons.
So far, I get better dry traction in my snows (Dunlop M3s) at cold temps (30 deg) than my OEM tires.
Which Blizzaks are you looking at? The LM-22s? Go for the cheapest, if you are concerned about the price.
TPMS doesn't bug me: the light blinks. No beeps. I may put tape/sticker over it.
You want snow tires, and 17" package lets you go for a narrower tire. Narrower tire means better snow traction.
Yep. I was looking at the Blizzak LM-22s.
I think I'm leaning towards the Dunlop M3s now, though, thanks to your feedback, which is consistent with most of what I've been hearing and reading.
Thanks, dude.
#18
Originally Posted by woodysjh
Last year I went without snow tires and got stuck\. This year I got Blizzaks and what a big difference, I actually like to go out and drive in the snow now. I put two 40 lb salt bags in the trunk and it seems to help give the backend more traction. I am now not afraid like I was last year to go out and tear it up. I have been passing trucks and suvs they all seem to be in the way now. ![Rock](https://www.rx8club.com/images/smilies/rock.gif)
![Rock](https://www.rx8club.com/images/smilies/rock.gif)
Thanks.
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I've never gotten around to getting snow tires and I can't afford them right now if I wanted them, so as of yesterday. my 8 is parked for a while. Had I had snow tires as of yesterday, I probably wouldn't have been happy because I would have driven it, and when I left work, the 8" of snow in the parking lot would have probably made things difficult even with snow tires. I'll be driving the Durango for the rest of the winter, which is great in the snow.
#20
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Originally Posted by joeman
i also just taken mine out(with stock tires) for the first time in about 2" of snow.
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency.
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency.
Use search and you can find many topics on this.
#21
I already searched!!!!!!!
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Originally Posted by RotoRocket
Woody - Which Blizzaks do you have?
Thanks.
Thanks.
They are great even on dry roads. They feel alittle more squishy than the stock tires I have, but they should since there is more rubber between the rim and the road.
Last edited by woodysjh; 12-03-2005 at 10:37 AM.
#22
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Originally Posted by joeman
i have driven in snow for 25 year in every kind of car. i had to put in in neutral just to stop so many time. this was even on fairly level ground. it is the worst car in the history of cars in the snow. period. i have banned any family member from driving it in the snow unless it is an emergency. joe
The low torque of the RX-8 should be a blessing in the snow, but the stock tires should be swapped for all season or winter tires.
Of course, I no longer to worry about driving in snow, pehaps the days in the GTO did me in - lol.
#23
Purveyor of fine bass
Originally Posted by joeman
i also just taken mine out(with stock tires) for the first time in about 2" of snow.
you have to understand that the stock tires are not all-seasons. they are all-out summer tires.
to give you an example. my roommate used to own a FWD VW Golf GTI. Not too much power (about 170hp), but torquey. he had summer tires on them. it snowed and he decided "well, I can probably make it a couple of miles down the road to class." he said he has never had a scarier drive. he was sliding for like 50 ft at the stoplight. he'd hit the brakes, the car would just LOCK up and slide and slide and slide. and that was on about 1" of snow.
so while most cars do come with stock tires that are all-seasons, and thus most of the time you can be OK driving on stock tires with high caution, the rx8's stock tires are summers and are not OK even for dry traction below 30deg.
#24
Rear wheel drive posi traction in the snow is harsh on any car. Doesn't really matter what tires you put back there, unless you have snow chains on, your going to loose it with any type of real gas.
The mistake people make when they compare the 8 to an older rear wheel drive, on either side of the argument, is that they forget those old trucks (even 4x4's) and cars are really one wheel drive on each axle. That makes a huge difference. My first RX7 didn't have posi and I drove it for 6 years with out loosing control in the snow or rain. My second one was posi and it was a nightmare controlling that car. Half the time I couldn't accelerate with all the other cars going up the on ramp or I'd fish tail. My tires were always class A wet traction.
When a posi traction car accelerates, technically, two primary vectors of force are applied on the plane of contact. One is caused by the torque from the axle and is applied tangential to the axis of rotation. This is moves you forward. The second vector is caused by the resistance of the tire to slide as you turn. Often this is a vector radiating out from the instantaneous center of rotation of the tire.
Simply put, the force on a tire that does not have torque applied to it (braking or accelerating) is simply offset by the force of friction. It is just a calculation of the centrifugal force. When you had torque to the tire you get a resultant vector that's a product of the two. Or, since thy are on the same plane (roughly), Pythagoreans theorem works well.
What you end up with is a resultant vector that is far greater than either of the two. So, in plain english, you have increased the force ont he tire. Mathematically, there is no way that a posi traction car can handle as well as a single axle car under the same conditions simply because under ANY acceleration you are subjecting the tires plane of contact to a larger force than if the tire had no torque applied.
The second problem I have with posi traction is that it tries to move both wheels at the same rate of rotation. However, the limited slip (upon cornering) will allow the inside tire to rotate less. This occurs because of the increased resistance to rotation from the smaller circumference of the inside tire's travel path (caused by a smaller radius to the instantaneous center) actually causes a resistance to rotation. The differential then slips (like a clutch). So, now you have yet another vector that is added to the inside tire. The end result is that the inside tire always breaks away first because it wants to spin as fast as the outside tire but is not covering enough ground to match the speed. Then when this tire gives way, you go from a friction coefficient to a sliding coefficient. You now transfer more "responsibility" to the outside tire. That's when that tire looses it.
The only gain you get from having both wheels spin is that if you are travelling (in a straight line) you can get stuck less. Having a 4 wheel drive helps because it provides traction in the direction of rotation for the front wheels and provides an even pull on all four wheels.
The mistake people make when they compare the 8 to an older rear wheel drive, on either side of the argument, is that they forget those old trucks (even 4x4's) and cars are really one wheel drive on each axle. That makes a huge difference. My first RX7 didn't have posi and I drove it for 6 years with out loosing control in the snow or rain. My second one was posi and it was a nightmare controlling that car. Half the time I couldn't accelerate with all the other cars going up the on ramp or I'd fish tail. My tires were always class A wet traction.
When a posi traction car accelerates, technically, two primary vectors of force are applied on the plane of contact. One is caused by the torque from the axle and is applied tangential to the axis of rotation. This is moves you forward. The second vector is caused by the resistance of the tire to slide as you turn. Often this is a vector radiating out from the instantaneous center of rotation of the tire.
Simply put, the force on a tire that does not have torque applied to it (braking or accelerating) is simply offset by the force of friction. It is just a calculation of the centrifugal force. When you had torque to the tire you get a resultant vector that's a product of the two. Or, since thy are on the same plane (roughly), Pythagoreans theorem works well.
What you end up with is a resultant vector that is far greater than either of the two. So, in plain english, you have increased the force ont he tire. Mathematically, there is no way that a posi traction car can handle as well as a single axle car under the same conditions simply because under ANY acceleration you are subjecting the tires plane of contact to a larger force than if the tire had no torque applied.
The second problem I have with posi traction is that it tries to move both wheels at the same rate of rotation. However, the limited slip (upon cornering) will allow the inside tire to rotate less. This occurs because of the increased resistance to rotation from the smaller circumference of the inside tire's travel path (caused by a smaller radius to the instantaneous center) actually causes a resistance to rotation. The differential then slips (like a clutch). So, now you have yet another vector that is added to the inside tire. The end result is that the inside tire always breaks away first because it wants to spin as fast as the outside tire but is not covering enough ground to match the speed. Then when this tire gives way, you go from a friction coefficient to a sliding coefficient. You now transfer more "responsibility" to the outside tire. That's when that tire looses it.
The only gain you get from having both wheels spin is that if you are travelling (in a straight line) you can get stuck less. Having a 4 wheel drive helps because it provides traction in the direction of rotation for the front wheels and provides an even pull on all four wheels.
#25
Originally Posted by spieder
Rear wheel drive posi traction in the snow is harsh on any car. Doesn't really matter what tires you put back there, unless you have snow chains on, your going to loose it with any type of real gas.
The mistake people make when they compare the 8 to an older rear wheel drive, on either side of the argument, is that they forget those old trucks (even 4x4's) and cars are really one wheel drive on each axle. That makes a huge difference. My first RX7 didn't have posi and I drove it for 6 years with out loosing control in the snow or rain. My second one was posi and it was a nightmare controlling that car. Half the time I couldn't accelerate with all the other cars going up the on ramp or I'd fish tail. My tires were always class A wet traction.
When a posi traction car accelerates, technically, two primary vectors of force are applied on the plane of contact. One is caused by the torque from the axle and is applied tangential to the axis of rotation. This is moves you forward. The second vector is caused by the resistance of the tire to slide as you turn. Often this is a vector radiating out from the instantaneous center of rotation of the tire.
Simply put, the force on a tire that does not have torque applied to it (braking or accelerating) is simply offset by the force of friction. It is just a calculation of the centrifugal force. When you had torque to the tire you get a resultant vector that's a product of the two. Or, since thy are on the same plane (roughly), Pythagoreans theorem works well.
What you end up with is a resultant vector that is far greater than either of the two. So, in plain english, you have increased the force ont he tire. Mathematically, there is no way that a posi traction car can handle as well as a single axle car under the same conditions simply because under ANY acceleration you are subjecting the tires plane of contact to a larger force than if the tire had no torque applied.
The second problem I have with posi traction is that it tries to move both wheels at the same rate of rotation. However, the limited slip (upon cornering) will allow the inside tire to rotate less. This occurs because of the increased resistance to rotation from the smaller circumference of the inside tire's travel path (caused by a smaller radius to the instantaneous center) actually causes a resistance to rotation. The differential then slips (like a clutch). So, now you have yet another vector that is added to the inside tire. The end result is that the inside tire always breaks away first because it wants to spin as fast as the outside tire but is not covering enough ground to match the speed. Then when this tire gives way, you go from a friction coefficient to a sliding coefficient. You now transfer more "responsibility" to the outside tire. That's when that tire looses it.
The only gain you get from having both wheels spin is that if you are travelling (in a straight line) you can get stuck less. Having a 4 wheel drive helps because it provides traction in the direction of rotation for the front wheels and provides an even pull on all four wheels.
The mistake people make when they compare the 8 to an older rear wheel drive, on either side of the argument, is that they forget those old trucks (even 4x4's) and cars are really one wheel drive on each axle. That makes a huge difference. My first RX7 didn't have posi and I drove it for 6 years with out loosing control in the snow or rain. My second one was posi and it was a nightmare controlling that car. Half the time I couldn't accelerate with all the other cars going up the on ramp or I'd fish tail. My tires were always class A wet traction.
When a posi traction car accelerates, technically, two primary vectors of force are applied on the plane of contact. One is caused by the torque from the axle and is applied tangential to the axis of rotation. This is moves you forward. The second vector is caused by the resistance of the tire to slide as you turn. Often this is a vector radiating out from the instantaneous center of rotation of the tire.
Simply put, the force on a tire that does not have torque applied to it (braking or accelerating) is simply offset by the force of friction. It is just a calculation of the centrifugal force. When you had torque to the tire you get a resultant vector that's a product of the two. Or, since thy are on the same plane (roughly), Pythagoreans theorem works well.
What you end up with is a resultant vector that is far greater than either of the two. So, in plain english, you have increased the force ont he tire. Mathematically, there is no way that a posi traction car can handle as well as a single axle car under the same conditions simply because under ANY acceleration you are subjecting the tires plane of contact to a larger force than if the tire had no torque applied.
The second problem I have with posi traction is that it tries to move both wheels at the same rate of rotation. However, the limited slip (upon cornering) will allow the inside tire to rotate less. This occurs because of the increased resistance to rotation from the smaller circumference of the inside tire's travel path (caused by a smaller radius to the instantaneous center) actually causes a resistance to rotation. The differential then slips (like a clutch). So, now you have yet another vector that is added to the inside tire. The end result is that the inside tire always breaks away first because it wants to spin as fast as the outside tire but is not covering enough ground to match the speed. Then when this tire gives way, you go from a friction coefficient to a sliding coefficient. You now transfer more "responsibility" to the outside tire. That's when that tire looses it.
The only gain you get from having both wheels spin is that if you are travelling (in a straight line) you can get stuck less. Having a 4 wheel drive helps because it provides traction in the direction of rotation for the front wheels and provides an even pull on all four wheels.