Snow tire performance
11-28-2018, 07:31 PM
#1
Burning Brakes
Thread Starter
Snow tire performance
The latest issue of Car and Driver published a story comparing summer tire and snow tire performance on a 991.2 C2 and a Corvette Grand Sport.
On its summer tires, the 19-inch Yokohama Advans, the C2 demonstrated 1.00 G in cornering grip and stopped from 40 mph in 43 feet, equivalent to 1.24 g.
The Grand Sport, with its much larger Michelin Pilot Super Sports, cornered at 1.11 g and stopped in 41 feet, which averaged 1.30 g.
When the C2 was fitted with Pirelli Sottozeros, the dry pavement grip dropped to 0.95 g and the stopping distance increased to 56 feet, or 0.95 g.
The Grand Sport got Michelin PIlot Alpin PA4s and on dry pavement managed 0.96 g and topped in 53 feet, or 1.01 g. I was surprised at the amount of cornering grip that both snow tires achieved.
On the snow, with the snow tires, these numbers plummeted. The C2 could only corner at 0.28 g and needed 169 feet to stop from 40 mph, or only 0.32 g.
The Grand Sport, with its much wider tires, suffered even more. Cornering grip dropped to 0.25 g and the stopping distance increased to 213 feet, or 0.25 g.
On a snow-covered road course, these figures were confirmed with the Grand Sport lapping in 1:35.2 seconds and the C2 going almost 7 seconds faster.
I think the 911 would do even better in the snow with narrower snow tires. Unfortunately, neither narrower tires nor matching wheels exist for 991s. That said, narrower snow tires would probably suffer an even greater loss of grip on dry pavement and for must of us, I suspect that even in the winter, we spend more time in the dry than on snow.
On its summer tires, the 19-inch Yokohama Advans, the C2 demonstrated 1.00 G in cornering grip and stopped from 40 mph in 43 feet, equivalent to 1.24 g.
The Grand Sport, with its much larger Michelin Pilot Super Sports, cornered at 1.11 g and stopped in 41 feet, which averaged 1.30 g.
When the C2 was fitted with Pirelli Sottozeros, the dry pavement grip dropped to 0.95 g and the stopping distance increased to 56 feet, or 0.95 g.
The Grand Sport got Michelin PIlot Alpin PA4s and on dry pavement managed 0.96 g and topped in 53 feet, or 1.01 g. I was surprised at the amount of cornering grip that both snow tires achieved.
On the snow, with the snow tires, these numbers plummeted. The C2 could only corner at 0.28 g and needed 169 feet to stop from 40 mph, or only 0.32 g.
The Grand Sport, with its much wider tires, suffered even more. Cornering grip dropped to 0.25 g and the stopping distance increased to 213 feet, or 0.25 g.
On a snow-covered road course, these figures were confirmed with the Grand Sport lapping in 1:35.2 seconds and the C2 going almost 7 seconds faster.
I think the 911 would do even better in the snow with narrower snow tires. Unfortunately, neither narrower tires nor matching wheels exist for 991s. That said, narrower snow tires would probably suffer an even greater loss of grip on dry pavement and for must of us, I suspect that even in the winter, we spend more time in the dry than on snow.
11-28-2018, 08:20 PM
#2
Instructor
Fun information! Wish they'd also done summer tires in the snow just to highlight how important they are, as in this excellent comparison: https://youtu.be/atayHQYqA3g
01-20-2019, 10:59 AM
#3
Drifting
The latest issue of Car and Driver published a story comparing summer tire and snow tire performance on a 991.2 C2 and a Corvette Grand Sport.
On its summer tires, the 19-inch Yokohama Advans, the C2 demonstrated 1.00 G in cornering grip and stopped from 40 mph in 43 feet, equivalent to 1.24 g.
The Grand Sport, with its much larger Michelin Pilot Super Sports, cornered at 1.11 g and stopped in 41 feet, which averaged 1.30 g.
When the C2 was fitted with Pirelli Sottozeros, the dry pavement grip dropped to 0.95 g and the stopping distance increased to 56 feet, or 0.95 g.
The Grand Sport got Michelin PIlot Alpin PA4s and on dry pavement managed 0.96 g and topped in 53 feet, or 1.01 g. I was surprised at the amount of cornering grip that both snow tires achieved.
On the snow, with the snow tires, these numbers plummeted. The C2 could only corner at 0.28 g and needed 169 feet to stop from 40 mph, or only 0.32 g.
The Grand Sport, with its much wider tires, suffered even more. Cornering grip dropped to 0.25 g and the stopping distance increased to 213 feet, or 0.25 g.
On a snow-covered road course, these figures were confirmed with the Grand Sport lapping in 1:35.2 seconds and the C2 going almost 7 seconds faster.
I think the 911 would do even better in the snow with narrower snow tires. Unfortunately, neither narrower tires nor matching wheels exist for 991s. That said, narrower snow tires would probably suffer an even greater loss of grip on dry pavement and for must of us, I suspect that even in the winter, we spend more time in the dry than on snow.
On its summer tires, the 19-inch Yokohama Advans, the C2 demonstrated 1.00 G in cornering grip and stopped from 40 mph in 43 feet, equivalent to 1.24 g.
The Grand Sport, with its much larger Michelin Pilot Super Sports, cornered at 1.11 g and stopped in 41 feet, which averaged 1.30 g.
When the C2 was fitted with Pirelli Sottozeros, the dry pavement grip dropped to 0.95 g and the stopping distance increased to 56 feet, or 0.95 g.
The Grand Sport got Michelin PIlot Alpin PA4s and on dry pavement managed 0.96 g and topped in 53 feet, or 1.01 g. I was surprised at the amount of cornering grip that both snow tires achieved.
On the snow, with the snow tires, these numbers plummeted. The C2 could only corner at 0.28 g and needed 169 feet to stop from 40 mph, or only 0.32 g.
The Grand Sport, with its much wider tires, suffered even more. Cornering grip dropped to 0.25 g and the stopping distance increased to 213 feet, or 0.25 g.
On a snow-covered road course, these figures were confirmed with the Grand Sport lapping in 1:35.2 seconds and the C2 going almost 7 seconds faster.
I think the 911 would do even better in the snow with narrower snow tires. Unfortunately, neither narrower tires nor matching wheels exist for 991s. That said, narrower snow tires would probably suffer an even greater loss of grip on dry pavement and for must of us, I suspect that even in the winter, we spend more time in the dry than on snow.
God bless,
TT
Last edited by TomTarzian; 01-20-2019 at 11:17 AM.
01-20-2019, 03:08 PM
#4
Rennlist Member
People say that the best solution is two sets of tires: dedicated summers and separate snow tires with their own mates wheels. The winter wheels can often be narrower than summer with smaller wheel diameter. The thing to be careful about with some 911s is the rear wheel width. You can go narrower as long as it’s not so narrow that rear bias causes a loose rear end. They don’t need to be as staggers as default either.
01-20-2019, 04:01 PM
#5
Burning Brakes
Thread Starter
Tire technology keeps getting better and better. All seasons are not excluded from the list and the best AS tires can perform better than cheap summer-only tires from just 5 years ago.
People say that the best solution is two sets of tires: dedicated summers and separate snow tires with their own mates wheels. The winter wheels can often be narrower than summer with smaller wheel diameter. The thing to be careful about with some 911s is the rear wheel width. You can go narrower as long as it’s not so narrow that rear bias causes a loose rear end. They don’t need to be as staggers as default either.
In a perfect world, you'd put something like 205/50-19s on 6.5-inch wheels in front and 245/45-19s on 8-inch wheels in the back. But neither wheel exists in 991.2 offsets, nor does the front tire size. And you can't go smaller in diameter in the rear because an 18 won't clear the suspension.
01-20-2019, 05:19 PM
#6
Rennlist Member
I can confirm the above as we just got 9 inches here Friday night. IMHO, nothing comes close to the performance of the C4S in the snow, except for Jeeps and Raptors with massive snow tires. The C4S loves to tear it up on the snowy roads. It all made for a fantastic early early morning pull before the masses got up and attempted their morning drives. Only reason I went home was the roadside began to get littered with multi-car accidents. We may have proper equipment, but others not so much, and no need to be out risking an accident unless necessary.
Been using this setup with the SottoZeros:
Front axle: 8.5 J x 20 RO 49 with 245/35 R 20 91V M+S tires
Rear axle: 11 J x 20 RO 56 with 295/30 R 20 97V M+S tires.
Pretty much right off the PorscheUSA website:
http://content2.us.porsche.com/prod/...D8A&ac=product
Great traction off the line in the snow and they have good grip when braking.
Been using this setup with the SottoZeros:
Front axle: 8.5 J x 20 RO 49 with 245/35 R 20 91V M+S tires
Rear axle: 11 J x 20 RO 56 with 295/30 R 20 97V M+S tires.
Pretty much right off the PorscheUSA website:
http://content2.us.porsche.com/prod/...D8A&ac=product
Great traction off the line in the snow and they have good grip when braking.
01-20-2019, 10:11 PM
#7
Rennlist Member
I can confirm the above as we just got 9 inches here Friday night. IMHO, nothing comes close to the performance of the C4S in the snow, except for Jeeps and Raptors with massive snow tires. The C4S loves to tear it up on the snowy roads. It all made for a fantastic early early morning pull before the masses got up and attempted their morning drives. Only reason I went home was the roadside began to get littered with multi-car accidents. We may have proper equipment, but others not so much, and no need to be out risking an accident unless necessary.
Been using this setup with the SottoZeros:
Front axle: 8.5 J x 20 RO 49 with 245/35 R 20 91V M+S tires
Rear axle: 11 J x 20 RO 56 with 295/30 R 20 97V M+S tires.
Pretty much right off the PorscheUSA website:
http://content2.us.porsche.com/prod/...D8A&ac=product
Great traction off the line in the snow and they have good grip when braking.
Been using this setup with the SottoZeros:
Front axle: 8.5 J x 20 RO 49 with 245/35 R 20 91V M+S tires
Rear axle: 11 J x 20 RO 56 with 295/30 R 20 97V M+S tires.
Pretty much right off the PorscheUSA website:
http://content2.us.porsche.com/prod/...D8A&ac=product
Great traction off the line in the snow and they have good grip when braking.
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01-20-2019, 10:26 PM
#8
Drifting
Narrower snow tires obviously work better in the snow than wide ones, but the problem is that the stock wheels on a 991.2 are too wide to work with narrower tires. And if you put the front wheels and tires on the back, what do you put on the front to maintain a reasonable size differential?
In a perfect world, you'd put something like 205/50-19s on 6.5-inch wheels in front and 245/45-19s on 8-inch wheels in the back. But neither wheel exists in 991.2 offsets, nor does the front tire size. And you can't go smaller in diameter in the rear because an 18 won't clear the suspension.
In a perfect world, you'd put something like 205/50-19s on 6.5-inch wheels in front and 245/45-19s on 8-inch wheels in the back. But neither wheel exists in 991.2 offsets, nor does the front tire size. And you can't go smaller in diameter in the rear because an 18 won't clear the suspension.
God bless,
TT
Last edited by TomTarzian; 01-21-2019 at 12:21 AM.
01-20-2019, 10:27 PM
#9
Rennlist Member
Narrower snow tires obviously work better in the snow than wide ones, but the problem is that the stock wheels on a 991.2 are too wide to work with narrower tires. And if you put the front wheels and tires on the back, what do you put on the front to maintain a reasonable size differential?
In a perfect world, you'd put something like 205/50-19s on 6.5-inch wheels in front and 245/45-19s on 8-inch wheels in the back. But neither wheel exists in 991.2 offsets, nor does the front tire size. And you can't go smaller in diameter in the rear because an 18 won't clear the suspension.
In a perfect world, you'd put something like 205/50-19s on 6.5-inch wheels in front and 245/45-19s on 8-inch wheels in the back. But neither wheel exists in 991.2 offsets, nor does the front tire size. And you can't go smaller in diameter in the rear because an 18 won't clear the suspension.
(And looking at those tire sizes, for the state-of-the art 911 30 years ago, almost makes me laugh.)
01-20-2019, 10:43 PM
#10
Drifting
I ran this experiment on my 964 C4, when I lived in Alaska. I used the stock wheels (F 16 x 6, R 16 x 8) with a set of studded Nokians, only available in 205/55-16, all around. BTW the stock rears were 225/50-16, so not much of a reduction. Anyway, that setup worked incredibly well in serious winter conditions.
(And looking at those tire sizes, for the state-of-the art 911 30 years ago, almost makes me laugh.)
(And looking at those tire sizes, for the state-of-the art 911 30 years ago, almost makes me laugh.)
God bless,
TT
01-21-2019, 12:13 AM
#11
Rennlist Member
Nokians. Plan on getting those next. Read those are the tyres of choice for Porsche at the Winter events.
01-21-2019, 01:17 AM
#13
SJW, a Carin' kinda guy
Rennlist Member
Rennlist Member
TT, what are you running now and what issues are you having? I think the biggest issue you will have is deep snow and lack of ground clearance. Short of studded tires or chains, nothing really works on ice in my experience and if you are driving through deep snow, you want tall and narrow tires and lots of ground clearance on a 4x4, preferably with lockers or limited slip differentials. Rud chains on a Land Rover with LSDs running 235 85R16 was basically unstoppable for me. I keep chains for various of my vehicles around so if I really have to get some where I can. But I don’t see any 991 being great in deep snow just because of ground clearance.
01-21-2019, 11:58 AM
#14
Burning Brakes
Thread Starter
Given that the 911 rear tires carry 50 percent more weight than the fronts, running equal-sized tires all around isn't likely to end well.
01-21-2019, 06:40 PM
#15
Drifting
TT, what are you running now and what issues are you having? I think the biggest issue you will have is deep snow and lack of ground clearance. Short of studded tires or chains, nothing really works on ice in my experience and if you are driving through deep snow, you want tall and narrow tires and lots of ground clearance on a 4x4, preferably with lockers or limited slip differentials. Rud chains on a Land Rover with LSDs running 235 85R16 was basically unstoppable for me. I keep chains for various of my vehicles around so if I really have to get some where I can. But I don’t see any 991 being great in deep snow just because of ground clearance.
God bless,
TT