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    PSM, tyres & various Turbos

    I took the loaner Turbo out for a little run today. Some highway but mostly back roads. I took N66 out to Spa. Beautiful sunny day but still cold.

    First observation is that I like the more oversteer oriented balance of the car with the snow tyres. This isn't surprising really given the smaller tyres at the back. It seems both more naturally balanced that way and also easier to overpower the tyres and induce oversteer.

    But nonetheless, I really don't like the feel of it. The combination of the Continentals carcases and the sipped tread of the snows really makes the car much more vague. In a way it feels good in that you can play with it but it also isn't confidence inspiring. At speed on the highway it especially has a way of rotating that I don't like. Makes me appreciate the Pirellis a little more.

    I also believe now that the different Turbos have different setups on their PSM. This car seems a lot more intrusive than does my own Turbo. Today I was powering out of a slowish corner and had the back just a little out where I wanted it and the PSM cut in and "fixed" it for me. In fact, I think the PSM made things worse because I reacted to maintain the stance while it reacted to terminate it. My own car would not have done that until things had gone much, much further. So I do think that there is a lot of variability in these cars. Which might go a long way towards explaining why some complain about it and others never do. It might not all be driver related after all.


    Re: PSM, tyres & various Turbos

    The reaction of the PSM system has to do with the snow tires and the different tire/rim size on the rear.
    I also like the Pirelli winter tires much more on the Turbo but I don't recall if they're still approved or not.

    You should see my wife's SLK 32 AMG with snow tires: the ESP lamp jumps in all the time, even if it is dry. Very annoying. I had the summer tires for a few days on this car and it was completely different.

    Re: PSM, tyres & various Turbos

    I also believe that PSM is an adaptive system that allows more leniency for drivers that have proven themselves able to handle larger slip angles. I think the harder you drive the car well (without overreacting to oversteer), PSM lets you play more. So, Stephen, all of those hours at the 'Ring have tought your PSM to let you have your fun. This rental probably hasn't had the same experiences...

    So Grant, is this your philosophy for women too?

    I too suspected that the PSM was a learning system but I've been told that it is not. Now I believe that.

    Apparently, it does have one short-term learned trait and that is that if you overuse it then it will start cutting back on what you can do. Reading between the lines, this seems more about preserving the systems. If the thing is constantly braking one of the wheels then I suppose that sooner or later you could overheat the brakes.


    rims & tyres

    I thought that the whole point of the smaller tyre at the back was to maintain the same rolling distance ratio with the front?

    I actually think you could be right. I was getting power oversteer on that corner and I think it could have been the bumpiness of the road plus the spinning wheel that confused it a bit. But it certainly did react fully (though didn't slow the car which I guess would have been the next step).

    It was the first time ever I've had PSM come on and have it upset me. Previously it has either not done anything intrusive or else been very welcome when it did intrude. This is the first time that I wish it had just gone back into its little hole and left me alone.


    Re: rims & tyres

    Porsche recommends Pirelli 240 Winter Sport for "mostly highway driving" and Continentals for the deeper snow. I have Pirellis and I like them, they are pretty good for winter tires.

    You are better off with narrower tires in the snow, that's why they went from 295 to 265 in the rear.

    Best regards from under 2 feet of snow

    Re: PSM, tyres & various Turbos

    The motronic is an "adaptive" system but as far as I know, the PSM is not. If the PSM system would be an adaptive system, it would be very dangerous. Imagine you driving your car on the track for a whole day and then your spouse/son/daugther/etc. who are not experienced. How would the PSM react in a critical situation? Right.

    The motronic however (and even the software of the Tiptronic) adapts to the driver, fuel, air temperature, air pressure, etc..

    Motronic & PSM

    Yes, but even the Motronic isn't a learning system (i.e. doesn't adapt itself to prior experiences). Certainly it takes multiple inputs and works with those but then so do a number of systems including PSM.

    I agree with you about PSM. Plus, I think that the goal in designing it was to intervene as late as possible and still be able to save the day. The goal for other systems seems to be to minimise risk by intervening early with as little as possible. The Turbo system seems to wait quite a while and then be very aggressive about it.

    If you think about it, if the system is already set to come in very late and then be very aggressive then how much more late and agressive can it get? And even if it were to be able to set itself to be even more aggressive, so long as it still "saved the day" then what would be the problem? Even the wife & kiddies should be happy.

    Actually, it would be nice if there was a little switch somewhere that allowed us to switch the PSM from its current late & aggressive mode to something that would kick in earlier. This could be useful for road driving in heavy rain for example. We've all heard the stories about spin-outs in this car in the rain where the system could not handle the conditions. Maybe earlier intervention would be enough to have saved the day? If I'm just trundling down the highway in heavy rain trying to get home then I would be happy to have a more secure system at work.




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