Of course it will transfer power forward anytime the rear wheels are rotating faster than the fronts as in the case of a loss of traction. That's a given. The vanes in the viscous coupler that are connected to the cardan shaft will drive the vanes connected to the front differential via the viscous fluid. There is no dispute there. What I was saying is that when the car is just driving down the road, for example at a steady 70mph without any loss of traction, how could the engine be transferring torque to the front wheels if they were smaller and thus rotating faster than the rears? Someone please explain that one. In that case the front vanes would be driving the rears via the viscous fluid effectively providing driveline drag until point where the rears began to rotate faster than the fronts as in loss of traction. Remember, Porsche states that the car transfers 5% power to the front at all times with up to 40% as the speed increases or a loss of traction occurs. When it comes to the winter tire sizes that Porsche specs for these cars, maybe they accept a tiny amount of front driveline drag because they know that when the cars is driven on snow or in other low traction situations then the rears will very easily loose traction and begin to rotate faster than the fronts thus transferring power to the front. I am certainly not trying to argue here but I do know how a viscous coupler works and I also know with 100% certainly that our cars have the same 3.44 ratios in the front and rears as it is clearly published by Porsche (unless what they publish is in error). There is absolutely nothing magical about our AWD system. With the same final front and rear drive ratios it must rely purely on the difference in the rate of rotation between front and rear to transfer power.

 

What is strange is why would Porsche recommend something that can potentially be bad for the AWD system? Especially with the type of cars that are more likely to see dry roads than wet or snowy ones even in the winter. Why did Porsche not recommend a winter combo with smaller rear wheels? It's not like they did not have a choice. Very puzzling!

 

Btw, anyone have (1) 50-100% 315/25/19 ps2 laying around to sell me? In so cal? Just blew out my side wall on a canyon run yesterday.

 

I have 2 near mint 315/25/19 PS2s with about 600 miles on them. No cuts, scrapes, or patches whatsoever.

 

Michelin has started manufacturing the ps2 315/25/19 again and they are back in stock at some tire dealers.

 

Just bought a new set from discount tire online and had free shipping, got them from ohio to arizona in 4 business days......

 

Yep ordered one up from discounttiredirect for $570 today. Yikes!

 

I have a 315/25/19 PS2 with at least 70% remaining with a patched that I'll sell for $200 if anyone needs it. Didn't even know the tire was patched until I had the tire unmounted so obviously no leaks or anything wrong with the tire.

 

Just ordered a pair from DiscountTireDirect.com and they confirmed they are available again right now.

 

I ordered a set and they arrived last week from Discount Tire Direct. The production dates were week 40 of 2012, which are recent productions.

I used to order them from Tire Rack but once they stopped carrying them, I've started going through Discount Tire Direct.

They aren't exactly cheap, but they are available!

- Chris

 

Finally got mine 2 weeks ago - made another round of calls to the usual suppliers and they were not able to source the tires, a local tire shop (Ventura County) said he could get them so I said go for it and he had them in the shop in 24hrs, manufacturer week 3812 if I recall. Also went for a new set of OZ wheels.