Torags

On the contrary, that has not been my experience. Mikes quote from the manual suggests you turn OFF the PSM, in heavy snow or sand.

bullbear

That's exactly what I think as well! On the CT, with fairly deep snow, wheel spin comes easy (and I was not really stomping on it either) but the AWD system will detect it and start to transfer torque to the front. But like u said, it won't do that until spin occurs which I think is why quattro feels so much more confident because it is working all the time...

As for fuel economy, the S4 doesn't even come close to the CT but I don't think the drivetrain is the big factor here

JeffES

Mud, I was referring to the previous poster (Ham), not you.... I didn't hit "post" quickly enough.
J

mudman2

no sweat

Brent 89-GT

Torags,

I think I mentioned in my post that in deep snow PSM should be shut off....actually I suggested locking the center diff which I believe shuts down PSM anyway.

The reason the manual says this was alluded to in a previous posts. PSM and any electronic traction control use ABS wheel speed sensors as a primary input. That means wheels have to be turning to benefit. In deep snow and sand PSM can cause you to become stuck because it doesn't allow enough wheelspin to keep momentum. This is for low speed extreme conditions, not what I would expect to find on the road.

It would take A LOT of snow to get me to disable PSM on the road. I live in the mountains and drive the passes 4-5 days a week. We get a bunch of snow, and I have been driving in snow for over 20 years now. I think it is a little irresponsible to suggest to someone new to winter driving, that they disable the system most likely to save their butt on slippery roads. There is a TON of evidence to suggest that stability management systems are the safest new addition to the automobile since seat belts. I would not switch off PSM except in EXTREME conditions. I would certainly not reccomend that someone new to the Cayenne and winter driving do it, that is just asking for trouble. Just my opinion

k2kv

Bullbear -

Your Scorpion AT tires are NOT snow tires. They won't stay soft in the snow, and the tread is designed for All Terrain use (dirt, rocks, etc.). They will work, of course, but they are not dedicated snow tires, and as such, you can expect more wheel spin than you would normally experience with dedicated snows.

I have yet to experience wheel slip with the Scorpion Ice & Snow tires on my CT. Oh, no doubt I could induce a wheel spin just for fun, but in general, the vehicle has been extremely stable here so far, and we've had lots of snow this season. I was out early in the day yesterday, at the tail end of a six-inch snowfall, and I just flew around all the turtles, never breaking traction once.

My CT has been great!

Cheers,

Jeff

Brent 89-GT

I am running the Scorpion AT's as well. They are not a dedicated snow tire, that is correct. They are M&S rated though so to say they will not work in the cold is a bit off. I would agree that in sub-zero temps a dedicated snow is certainly better and if that is where you live, that is the way to go. I have a slightly different situation. We get a lot of snow but generally never temps below 15-20*F(above zero). I like the more aggressive tread of the AT for the deep snow where sipes are not as effective. I rarely see ice where dedicated snows are better. The AT's were cheaper and will almost certainly last longer. Depending on the conditions you operate in I think a case can be made for the AT's.

k2kv

Brent,

I don't believe I said they will not work in the cold. What I said was, "they will not stay soft in the snow..." I added, "they will work, of course..."

M&S tires are a good compromise tire (hey - what tire isn't?). But, they are not as sticky as high-performance summer tires on dry pavement in the summer, nor do they provide the same ice traction as do winter tires in the winter. They work well for many folks, though, under a great variety of operating conditions, and certainly offer greater longevity.

Personally, I think ATs are a good choice for many drivers. Here on Long Island, our roads get pretty icy at times (and sometimes quite suddenly), and I would simply prefer to run on tires dedicated to that purpose when in season.

Cheers,

Jeff

bullbear

k2kv:

I totally agree with you that the ATs are not dedicated snows and that's why I specifically clarified that so that it is a fair comparison.

Brent:

I also agree with you that in deeper (6-12" freshly fallen) the more aggressive treads of ATs should actually be better than snow tires.


In any case, I still maintain that the difference in feel I get from the S4 and the CT is mainly from the different AWD systems. Now when I get my "true" CT in a few months, I'll be putting dedicated snow tires on the Turbo 18". I guess I'll have a more accurate comparison next winter.

Brent 89-GT

Jeff,

I know about ice, I lived in Minnesota for many years I guess I was just getting a little too particular and needlessly defending my tire choice, sorry.

I also live where there is ample opportunity for off-roading so even though the Cayenne has not been off-road, at least I have something more suitable than the 40 series 20's. If I didn't think that there was a chance in the next year or two of the truck seeing a trail, I would have gone with dedicated snows myself. Two sets of tires is plenty, I didn't even consider three(compromises as mentioned).

bullbear,

I wonder if the difference is because of the Cayennes rear torque bias? I am pretty sure Quattro is a 50/50 split normally where the Cayenne is closer to 40/60. I recently had a Jaguar X-type as a rental. That one, even though it is based on a front drive chassis is also a rear torque bias awd system. I drove it on some nasty roads (all season tires) and it seemed to perform very well. I've never owned an Audi becuase of the typical heavy front wieght bias and I don't think I could get used to the front drive feel, even with Quattro. I would guess the S4 and the Cayenne drive much differently. BTW, new V8 S4? That is something I might consider, especially in stealth Avant form.

k2kv

Brent,

I understand completely, and thanks! Minnesota - yikes! You have my great respect.

You're absolutely right about going off-road. I went through lots of gyrations regarding tires when I first bought the Cayenne, and I have had to swap a couple of sets in order to get the two sets I now have (and two sets is quite enough for me, too). I felt I should do my best to solve the worst case situation first. And that, of course, is sudden ice.

I will not likely ever go off-road, but my summer tires are not dedicated summer tires! I am using Scorpion Zero Assimetrico, an all-season M&S rated tire that looks to me like it would spin in the snow. But I know I won't get stuck anywhere for lack of simple traction, and I also appreciate the much longer life I'll get with them compared to summer rubber.

Take care, and safe driving,

Jeff

426H

As Brent said earlier, the audi has a neutral tourque bias while the cayenne sends 62% of the power to the rear wheels to achieve more feedback to the driver. It's a better setup and you will get used to it.
If you compare cars in snow, tires are VERY important. It is not meningful to compare two different cars if the tires aren't the same. A magazine here in sweden recently had a WINTER test with a cayenne s, a volvo xc90 v8 and a land rover v8. The volvo and land rover drove in circles around the cayenne because they had studded winter tires (studded tires are approved here during the winter season). Porsche does not approve studded tires, so the cayenne was fitted with the approved pirelli scorpion snow & ice, which is a rather bad compromise for REAL winter conditions. All-season tires is of course even worse when driving on snow and ice.
My 0,02$

Renn 951

Your statement is true for normal, dry pavement, but it's misleading when you talk about performance in the snow. The Audi quattro is 50/50 between axles on dry pavement while the Cayenne is biased 62% towards the rear as you state. But when the quattro Torsen differential senses impending slip it immediately adjusts the bias, and will send as much as 65% to the axle with the best traction. The electronic system in the Cayenne will also adjust the bias in snow, but the point in the original discussion was that the electronic system offers a little more slip before it makes the adjustment than the purely mechanical quattro system.

I don't know that you can say the Cayenne system is "better" except that under normal, dry conditions it provides more of a RWD "feel" to the vehicle. In the snow I think you can make an argument that quattro is "better" from the standpoint of instantaneous response, yet the Porsche system is well engineered and effective even if it gives a feel of allowing a bit more slip before compensating.