jblaw

Hi All --

I've just joined the club with a Lapis Blue 2001 996 Turbo. I live in New York -- and while I don't drive much in the winter, I do like to be prepared and mount all my cars with snow tires. Looking at the thread and at Tire Rack, it looks like the only thing available is the Pirelli Snow Sports (an old design) with the rear 265 size, that many say don't fit the stock twist wheels. Has anyone had any success with other brands and sizes that fit the stock wheels?!?

Thanks,

Jeff

Carlo_Carrera

Use these in these sizes:

https://www.tirerack.com/tires/tires...omCompare1=yes

NineNine6TT

professorv

professorv

Carlo_Carrera

They are mistaken. The load rating is above spec snow tires.

jblaw

jblaw

professorv

Carlo_Carrera

Go with the 215/45-18 up front. They match perfectly with 275/35-18 in back and they are slightly taller and narrower than the 225 size which makes the 215 better for snow.

jblaw

Rustler

OP, here is some additional information for your consideration, or for someones else reading the thread:

In winter I am successfully running 235/40 R18 (f) and 275/35 F18 (r) Bridgestone Blizzak LMs, and have for several years.

The Blizzak high performance snows are a great balance between snow and ice grip and acceptable performance on dry roads when temps get a little warmer (the studless snows on my wife's Alltrack and my (former) STI are awesome in snow/ice, but pretty squishy when the temps climb above frigid).

I'm told by Tire Rack the 275 (Blizzak anyway) will stretch onto the rear Turbo Twist rim, but you'll have a lot of rim exposed, and it'll looked stretched out. I went with a 10 inch rear (offset ET 25) in the rear, and the 275 isn't meaty on there, but it doesn't look ridiculous. The 10 in rim with ET 25 sits reasonably flush. Mine are Forgestar 14 which can be made in custom offsets, and quite reasonably priced.

The sizing above is well within Porsche specification for difference in tire size. Some are adamant that you need the front slightly taller than the rear or you will damage the awd (viscous coupling). I respect there is a difference of opinion, but my research has showed otherwise. I believe it to be perfectly safe for the VC as long as the sizing is close. A difference in overall wheel size that is too great (for reference, Porsche factory specified wheel sizing has a .4% difference summer and .8% difference winter) will damage the VC by constantly engaging it (it works by heating up when there's a difference in speed between front and rear, and then engaging), but if the rear is slightly taller but still in the acceptable delta, the only negative effect might be in speed of engagement of the front in the event of slip in the rear. I drive in the snow all the time, and have never noticed this. With a .4% taller front (factory summer setup), the rear does a few more revs per mile. By design, the VC is always slightly engaged for immediate response, and when the rear wheels slip, they pickup even more revs per mile over the front, the VC gets hotter, firmer, and more power goes to the front. However, if in your snow setup (like the factory snow setup), you have rears that are .8% larger, the fronts will rotate a few revs more per mile, thus the VC is always a bit engaged as it is in the summer, but when the rear wheel slips, for a very brief moment the front and rear will spin at the same rate as the rear picks up speed, and in theory the VC would disengage because there would be no delta, and then the rear will start spinning faster, more revs per mile, there would be a delta again and the VC would engage sending power to the front. In the winter scenario there could be a lag in the pickup of the VC when the rears start to slip. I have NEVER felt that as a practical matter. And to be clear, a common misconception is that the VC will spin in the opposition direction, or some other mechanical error if you have larger rears, but that's not true. VC engages when there is a difference in wheel speed between front and rear, it doesn't care whether the front is faster or vice versa. With the slightly larger front you have constant engagement, which is in theory preferable, and why Porsche designed it that way, My research has shown that you will not damage the system by having a slightly taller rear.

My sources for this conclusion are: 1) Porsche factory approved summer and winter tire sizes; 2) a discussion with a noted Porsche expert and author of a often cited book on the 996; and 3) discussion with the head tech at the dealership where I bought my car.

As I said above, some disagree with this and are of the opinion that the fronts must be larger to prevent some sort of damage. With winter tires (or any tires) getting harder to find, I hope it may help increase the number of viable options to understand that the critical issue is the overall difference, regardless of which is larger, front or rear.

jblaw

Thank you all! I actually found a set of Porsche winter spec wide body turbo twists and bought them as well as snow tires! Can't wait to rocket this sled through the snow

geetee

Many combos you can use on 996. I've always run 235/40/18 275/35/18. 275/35 is the smallest rec. size for a 11 wide wheel. It's a stretch but fit's fine and I don't really care too much about the looks as winter tire