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Discussion Starter · #1 ·
Over the past week, I've stepped out the rear accelerating into a turn from a stop 3 times, vs. 0 times in the previous 9 months of ownership. Don't get me wrong, it's quite enjoyable, but I don't like it when it comes as a surprise, as it makes me wonder about other taken for granted stability.

With my 69 911 stepping the rear out accelerating around a turn from a stop was pretty much par for the course, but I was surprised how amazing the traction on the Cayman was when I first got it. Initially I was always driving with the expectation to have to deal with the tail happiness of the 911, but over time I've come to rely on its solid stability even under full throttle.

The road was dry in each situation, the tires are 9 months old and I checked the tread as well and its fine. Twice it was on cold tires, once on warm. Temperatures have dropped a good 15 degrees, usually 50 now instead of the usual mid-60s to 80s and with that I've also noticed that my tire pressure seems to start at ~30psi and rise to 32psi warm, while before i was around 34psi.

Have I just gotten more aggressive, is it the temperature change and/or tire pressure change?
 

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What tires?

Just curious because my one criticism of my new to me Boxster GTS is that the back end is a little loose. I took it to my local Porsche specialty shop when I got the car home and he felt the same. In my case part of it is alignment. I don't remember the exact details, but when he popped the hood he noticed the front alignment immediately. Something along the lines of suspecting the previous owner used it as a highway commuter car and complained of it crowning. He's right about the first part so I have no doubt he is right about the second. His recommendation was to drive the car for 90 days before making any changes. Get a feel for it and learn every squeak and rattle. Then after 90 days we can talk about changes and fixing squeaks or rattles. My plan is to replace the new(ish) Continental Extreme Sport tires with Michelins. Maybe do spacers. Then get it aligned to be more neutral.
 

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I don't think it is tire wear, but the cooler temps could be contributing. Surprised me when I first did it and it has happened a couple of times since. In my case, I think it was mainly increasing confidence (overconfidence) in the car's ability to cling on. Strongly accelerating while cornering can put you on the limit pretty quickly.

I now take it a bit easier on corner starts. The car still corners magnificently.
 

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Pirelli P/Zero all around. 500 miles on front, 5k miles on rear
I hated my Pirelli’s and had traction issues especially when cold! Rears only lasted a tad over 11,000 miles. Switched to Michelin Pilot Super Sports and could not be happier! I have 24,000 miles on them and they are about half worn! Mind blowing.


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From tire rack-
As ambient temperatures get colder, typically in the 40-45° Fahrenheit range, summer performance tires lose a noticeable percentage of traction as their tread compound rubber properties change from a pliable elastic to inflexible plastic. The tire industry uses the term "glass transition" to describe the temperature where a summer performance tire's grip/slip performance changes dramatically. This means the summer performance tires that provide predictable traction in warm to hot conditions will be found to be very challenging to drive in cold to freezing temperatures. This is especially true when the tires first begin to be driven or if the driver aggressively applies gas pedal pressure with today's turbocharged fours or high-torque sixes and eights. Fortunately, glass transition is a reversible condition that allows the tires' normal traction to return as the ambient temperatures climb.

I never drive summer tires below 50f. Different tires will perform differently, but as temp approaches upper 40's summer grip will disappear (glass transition), Using summer tires at or near freezing temps will void any warranty, but driving at too a temp and expecting the tire to perform other than as designed is risky. PSI drops with temp.
 

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I have also had the rear slip out a bit both accelerating into corners and out of a right hand corner (at 65 km/hr – too fast). I have learned that the car can easily build overconfidence and points out some of my crappy driving skills. ;)

I think the Cayman is probably one of the most forgiving cars in these types of situations but still needs to be treated with respect. My car came with Goodyear Eagle F1s and I have never been completely satisfied with them and am very curious to try the MPSS when it comes time for me to change.

I often think about taking some driver education courses but have not yet done so.
 
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Discussion Starter · #9 ·
From tire rack-
As ambient temperatures get colder, typically in the 40-45° Fahrenheit range, summer performance tires lose a noticeable percentage of traction as their tread compound rubber properties change from a pliable elastic to inflexible plastic. The tire industry uses the term "glass transition" to describe the temperature where a summer performance tire's grip/slip performance changes dramatically. This means the summer performance tires that provide predictable traction in warm to hot conditions will be found to be very challenging to drive in cold to freezing temperatures. This is especially true when the tires first begin to be driven or if the driver aggressively applies gas pedal pressure with today's turbocharged fours or high-torque sixes and eights. Fortunately, glass transition is a reversible condition that allows the tires' normal traction to return as the ambient temperatures climb.

I never drive summer tires below 50f. Different tires will perform differently, but as temp approaches upper 40's summer grip will disappear (glass transition), Using summer tires at or near freezing temps will void any warranty, but driving at too a temp and expecting the tire to perform other than as designed is risky. PSI drops with temp.
I didn't even think about P/Zero's being summer tires and was not aware of that "glass transition". That fits all the symptoms. The two times on cold tires it was ~50F and on "warm" tires, it was a night ride at about ~45F ambient. Not something I would have even considered driving in California :)
 

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Probably due to cooler weather. Summer tires tend to lose effectiveness as temps get colder. At around 40/45 degrees you need to drive very cautiously. Tire pressure goes down one psi for every ten degrees drop.

I'm curious about the mileage you have on your tires - 500 on fronts and 5,000 on rears. Generally you'll get twice as much mileage on the fronts than the rears. I can only guess that the fronts have recently been replaced while the rears are original. FWIW, I got ~11k on my rear tires while my fronts were still in very good shape.
 

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It's due to the colder temperatures as others have mentioned. I notice it <65 degrees. It gets really bad <45 degrees. Accelerating hard at these lower temperatures will also give you tire hop (at least when I had the Eagle F1s on the car). Cornering hard will make the car slide earlier (front and rear tires)

Winter tires will help but depending on which part of CA you are living it, it may not be necessary or worth the effort of changing tires 2X/year.
 

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Discussion Starter · #12 ·
I'm curious about the mileage you have on your tires - 500 on fronts and 5,000 on rears. Generally you'll get twice as much mileage on the fronts than the rears. I can only guess that the fronts have recently been replaced while the rears are original. FWIW, I got ~11k on my rear tires while my fronts were still in very good shape.
It's been a source of curiosity for me as well. I got the car 9 months ago with 23k miles and the dealer had just replaced the rear tires for the sale . The front were really in dire need when i did replace them at 27,500 miles. The tire shop speculated that the fronts were originals because the compound "looked old" to them. That seems rather incredible, 27.5k on P/Zero? But if so, i wonder if the rear were also original and the previous owner just grannied it back and forth to work. Still 23k on P/Zero seems hard to believe.
 

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Pretty sure the rears were NOT original. No matter how you drive, the rears will wear out twice as fast as the fronts. Two options though, go to a winter tire or slow down when the temperature is below 50 or so. Unless it gets really cold then you really should go to a winter tire to be safe.:cheers:
 

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I didn't even think about P/Zero's being summer tires and was not aware of that "glass transition". That fits all the symptoms. The two times on cold tires it was ~50F and on "warm" tires, it was a night ride at about ~45F ambient. Not something I would have even considered driving in California :)

Yep, that's it. I started grinning twice as big since our temps reliably went under 50. Inducing a rear to slide (more like "rotate", PSM almost never intervenes) with so little throttle and at such low speeds is pure cocaine. I always say that big grip is overrated :)

To get that same high on the track in August, I had to hit a corner really, really fast and get WOT sooner than I ever tried before. Pucker factor was big, but then I tried it every single time I hit that corner again. It is THAT satisfying. If you can get it at ludicrously low speeds and without any fear of dying ... it is that much better. IMO at least.
 

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three things here, where the 2 most important ones for that behavior haven't been mentioned yet. The first is tire temperature, which is probably the culprit when there's a difference in the same car, although also the other factors mentioned can exacerbate it (tire wear, heat cycles, tire pressure, traction-reducing issues, etc). Cold/cool tires have much less traction in summer rubber, as mentioned already. But I want to add even summer tires can be worse than UHPAS tires (like Michelin A/S3s, or Conti DWS06s) if not fully hot, like on a cool mountain run. The great majority of cars fitted with summer tires would be better off with UHPAS even in summer (and MUCH better the rest of the year), but most folks don't know that;). And those tires have the exact speed and traction rating of summer tires. Now, the other 2 things that limit how quickly you can take off from a standstill with front wheels turned. Second, all drivers should know that when you want to bring the tail around on purpose, you do it by gunning the throttle with the steering wheel turned, right???;) Therefore, you just can't take off that quickly while turning 90º right on a fast street (and no, PSM can't catch/correct such quick spin). The best approach is to aim the car at the merging street at the least possible angle (maybe 60 instead of 90º?), to be able to accelerate quicker before the front wheels are straight. Until then you can gun the throttle... but might still not have that much traction initially, which brings us to #3: PTV, which includes an LSD (limited slip diff). You can accelerate a lot quicker from low speeds with it than without, due to both rear wheels having traction, vs just 1 with an open differential. My brother's BGTS does not have PTV, and my CGTS does. BIG difference in traction/acceleration when taking off like that (or hairpins, etc). Finally, mid-engine cars have the best possible traction in those situations, so keep that in mind:). Just learn how quickly you can take off under different circumstances. Merging from a perpendicular street onto a fast avenue is a dangerous proposition in traffic, so always better to find a nearby traffic light instead. Even fast cars can trigger a chain-reaction before they're able to accelerate fully, mainly because most people don't know how quickly they can accelerate, and slam on the brakes causing an accident instead. Not worth it IMO, but to each his own. I've safely accelerated in such situations, leaving A TON of space from the car behind, and still hear tires screeching and horns blaring due to the car behind unnecessarily braking too hard, so typically try to avoid such mergings. Or wait until there's sufficient space for the idiot drivers here not to freak out;). Still remember driving in Mexico City: you didn't have to brake when somebody merged inches from your front bumper; everybody knew what they were doing, and everybody was respectful (not trying to accelerate to avoid you merging, etc). People were aggressive, but excellent drivers in general. You just trusted them, and never had an accident, or somebody even touching my bumper. Here is just ridiculous, especially now with the distractions of cell phones. And if you see a Buick, or any other 'old fart' car, you need to leave a mile of space, or be greeted with 10 minutes of horn noise, or even worse, an accident behind them. And nobody knows how to park:). Can't drive aggressive at all here, to avoid causing an accident.
 

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I didn't even think about P/Zero's being summer tires and was not aware of that "glass transition". That fits all the symptoms. The two times on cold tires it was ~50F and on "warm" tires, it was a night ride at about ~45F ambient. Not something I would have even considered driving in California :)
45F - the main factor without a doubt!
 

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My Pzero with 14K miles are downright nuts to drive in cold conditions. I got two scares (one was really bad) and now I have snow tires on... enough said.

P.S. I already have new Pzeros in the garage for the new season.
 

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It's warm year-round for me, being a snowbird... My 981 S always felt that way. Even with more torque and more power, my 991.1 C2S always is well behaved. Even when hitting it really hard....
Both cars shod with PZeros at recommended the pressures.
 

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Interesting timing with this thread as 2 days ago I lost control of my 981 and scraped along the central reservation of a dual carriageway.

While it all happened very quickly I was surprised that I was unable to control the car as the engine was cold so I never step on the gas until above 71c (see previous posts :) ) . While I'm working on the theory of driver error - cold tires, 5c outside temp, too much gas in a corner, there are some other things that I wonder if contributed.

Firstly my front tyre was flat but there was no damage to the wheel - possible flat tyre/blowout, or just the lateral forces during the incident? Also the the rear wheel was no longer perpendicular to the axle, probably caused buy hitting the curb as the alloy was scraped - however a colleague wondered if I'd considered a part failure as the angle of wheel would certainly have caused the car to behave as it did?

Porsche picked up the car and have taken it to the bodyshop, but people who know me and my previous car history Porsche/Ferrari's etc and my daily fondness for throwing the back out have suggested I consider getting it inspected first. I'm blaming myself but I now have a niggling doubt in my mind.
 
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