rk-d

Haven't driven my in a straight up downpour on the highway yet.

This seems to dovetail with some people complaining of high speed instability on the highway with their cars, in the dry -- an issue I haven't experienced.

I don't doubt the tires suck - Normally, I exchange out my tires for Michelins -- this is the first Porsche I've had that Michelin doesn't support, which is weird and annoying.

As odd as it sounds - I'd switch off the TC to remove that variable, though it's hard to see how that makes a difference -- usually you'd know when TC is kicking in.

Some random cars appear to be sensitive to tramlining which could be an alignment issue (ie caster) and perhaps that's exacerbated in the rain.

Metalblond

I'm wondering if it's something individual to certain cars? As people are mentioning their 991's, I have to say my 991.2 C4S was the worst in heavy rain and wind- (maybe not worse than a Corvette- but close to being equally as bad). My Cayman, on the the other hand, was and is a beast.

ko2302

Hello all, new here from Istanbul, Turkey. I recently bought a c4s 2019 model year produced in July 2019. It does not have rws.

During a highway travel with lots of rain, the car was very unstable while changing lanes, I could feel that the car was about to hydroplane. I have the factory installed Goodyear F1s with 13,000 km (almost 8,200 miles) on the car. I lowered the tire pressure to comfort pressures.

I was thinking that this is a tire issue given the mileage on my tires and everyone complaining about Goodyears. I was thinking to change to new set of Pirelli pzeros as they are the only alternative available for 992. My tire shop says that the tires still have good tread and after reading about this post I am quite confused. Is this a chronic issue with the car? Did anyone manage to get this issue solved?

AlexCeres

alignment, tire pressure and tires are all common problems. Not sure about the goodyears but the Michelin PS4S are popular for summer performance with acceptable wet behavior. I drive them year round in CA (two seasons, summer and rain)

The car should absolutely not be unstable in the wet while changing lanes. The awd C4S should gracefully handle a considerable amount of driver mis-input. I’ve done some .... ill advised ... things in a 2019 turbo (also awd) in pouring rain and the car just fixed all my mistakes.

If you’re new to 911, you might need to be a little more sensitive to the rear engine weight. I found it was a little more sensitive to my mistakes with throttle and brake input, specifically not being smooth enough, compared to the BMW M3. On a C4S you shouldn’t have any actual problems, but you may feel the weight punish you a pinch before traction control kicks in to cover you if you make a mistake.

gcurnew

I have C4 with Goodyear F1s and at 10,000 km the rears are at 6/32nd tread depth...add another 3k km and they will be down to between 4/32nds and 5/32nds, which is getting near the end of their usable life. When the car had about 5000km on it I spent a full day if very wet conditions and didn’t have any stability, lane-change or aqua planing issues.

I suggest checking tread depth on your tires...if around 4 or 5/32nds that could be a large part of the problem.

Penn4S

What are your cold tire pressures? If you are over 31 f and 34 r , adjust your pressures.

ko2302

thank you for the response. My cold pressures are 29 front and 32 rear which are comfort pressures.

SpiderG

Just to add another data point, I had a 992 C4S for a weekend through the Porsche Museum "Drive" program and experienced the same thing while driving through high cross winds at 70-80MPH on dry highway. For brief moments, probably just under a second each time it occurred, I felt like I did not have complete control over my steering inputs into the car... for lack of a better term, it felt "eerie" as you described. This was during very gentle lane changes. I've never felt anything like it in my 991.2 or any other car, ever. It felt spooky and caused me to lose confidence in the car during that portion of the drive.

detansinn

About 13k miles across 14 states in my C4S and I have never experienced an issue, even through 500 miles of non stop rain on a trip that I did earlier this year.

WCE

I'm going with tramlining - especially from the rear with those 305's.

rkdav

Assuming car tires behave like aircraft tires, the onset of hydroplaning will occur at nine times the square root of the tire pressure.

ko2302

Did any of the first posters in this thread find a solution for this issue?

sechsgang

Missed this being back up here...and for what I was experiencing, when I turned traction control OFF...the car became WAY more stable. I think Porsche has put too much electrical sensory nanny-isms in these cars and its a shame. NEVER had a feeling like that in any Porsche over the past 15 years, short of a gt3 with near chorded semi slicks in a full downpour. WET mode needs to be able to be taken away haha.

donnie8300

I’ve had the same exact issue. When rain is more than a 1/16 of an inch, strong feeling the car will hydroplane and sort of scary when doing lane changes or even driving over a thin puddle. It sort of like the car changes it’s character entirely in the rain. Never felt like this in a macan gts with similar tire pressures. Seems like the light weight plus wide tires can be a bad combo …but sounds like prior generations did not have the same issue. I have a base 992 2wd

ko2302

My problems seems to be reduced new tires switching from Goodyear F1s to Pirelli PZ4. What is the mileage on your tires and what tires do you have on?