I mounted my winter wheels and tires and have selected "20 inch winter tires" in the TPMS menu. I noticed as would be expected that the new winter tires do not lose traction when I floor it in first gear. My Pirellis were always breaking traction in the cold. But I also noticed that the three times I used LC with the winter tires, the car bogged down to 2k RPM when I stepped off the brake. I'm wondering whether the launch control is programmed differently when the "winter tires" box is checked vs. standard summer tires. Anyone have a clue?

When I go to Englishtown tomorrow I bet it will be crowded. I may not be able to get more than two runs in. Would hate to waste one with the winter setting if the winter setting is not going to let me launch like I should at the strip.

 

So I made three runs this morning. Launch control did not work. I set the tires to summer just in case that might affect the settings. For each launch, the Launch Control Activated would flash. I'd let off the brake, and the tires would spin for a second and then the RPM's would drop to 2k rpm. So it was like launching at idle but after wasting a second spinning. All 60' times were 1.8's, with a best of 1.837. I ran an 11.335 @ 125.75. Worst 60 was a 1.889. I went 11.552 at 127.29 on that run.

Stopped by the dealer afterwards. They plugged something into the OBD port to reset a bunch of modules. But I tried launch control again afterwards, and it did the same thing. GM thought that it might be a failsafe response to too much grip, but that doesn't seem right. It should deadhook if it sticks. Also, I was getting wheel spin on my Pirellis, which I thought the winters would cure. I know the winters are stickier because the tires don't spin at the top of first (when I just floor it)

I miss the roller coaster launch I used to have.

 

At the risk of sounding dumb...you are absolutely sure that you're not lifting off the throttle when you launch the car, right?
I agree that a failsafe due to much grip sounds like an improbable reason.
S.

 

A case of alligator legs? I don't think so. But I will try it again today and make sure I keep that foot planted. I may switch wheels this week and go back to englishtown in the next two weeks.

 

My intuition is that the tire spin is causing the problem. If I was writing the Launch Control software, I would include failsafes for poor traction to prevent an accidental over rev. Imagine some bozo attempting a launch in the rain and the tires break loose causing an over rev before the ECU or transmission can intervene. I suspect that when the ECU senses slippage above a certain threshold it cuts the throttle.

- Patrick

 

Tried it again this afternoon and almost put my foot through the floorboard. Same result.

Anyone know how to do a burnout in these cars? Maybe I need to get the tires hotter than they get in normal driving.

 

Read this. Seriously, you are trying to get burnouts with your winter tires? Measuring your times? Sorry, but this is just a waste of time. Winter tie compounds are much harder, you will have nowhere near the traction. Did you turn off the traction control? I guess a drag strip will let you run with any tires, most tracks will not let you run on the track with winter tires for obvious reasons.

 

Summer compound tires are much harder in 40 degree weather than winter tires. That's why we swap tires even if we have no intention of driving in snow and ice. I can floor it and not spin at the top of first with the winter rubber, where I was just lighting up the pirellis on the street. I. am switching back to my summer tires for my Atco rental, but I am pretty sure I will encounter the same problem. And probably even worse traction.

 

No question that winter compound tires are softer/more pliable below 40 degrees. Why do you expect the same engine cut-off in LC with your summer tires? Why not just try LC before you rent track time. What I have found interesting is that in 50 degree plus temperatures with dry roads rear tires break loose in spirited acceleration from a stop more than is apparent on LC starts. I say apparent because the only wheel spin I have felt in LC starts is very brief.

 

I am assuming the same wheelspin because that's what I started to experience before switching over to winters. As the temps dropped from the 70's in October, I noticed that the launch was not a catapult like it had been. It wasn't spinning at first, but I could feel that the car was hunting for traction from back to front and side to side. The RPM's did not drop, but the forward motion wasn't the same. When the temps dropped into the 40's, I was getting wheelspin and slower launches. I was also getting the flashing traction light when I floored it in first and second. The RPM's would climb, and it would start spinning tires.

When I drove off the dealership lot with the winter tires, the first thing I did was floor it in first, and it did not spin at all. I had grip again. So I was a bit surprised that they were spinning with launch control. I'm happy to switch back to summers and try again.

 

So the temps were warmer last night. Tried launch control twice. The first time,it was MUCH better. Tire spin but there was definitely forward momentum. Tried it again a little closer to home, and it was as it was on Saturday - spinning and then a drop to 2k rpm. I ordered impact sockets with protective sleeves. Will change the wheels at some point in the next couple of weeks and see if it is just a problem with the winter tires.

 

Did you turn off the traction control? Aren't you getting a drop in rpm because the traction control is kicking on? In sport plus the traction control is very non intrusive, but it can still come on.

While I was wrong earlier, winter tires have softer compounds, they have much more open tread and far less traction than a summer tire. Of course the relative traction is better than a summer tire in cold weather, the relative performance will be much worse. Winter tires have very soft sidewalls, perfect for cold weather, but this will make for horrible handling on a track. I even noticed this with an all season tire during the summer - horrible handling compared to a summer tire.

 

I have always left traction control on. My guess is that if I turned it off, it wouldn't cut out - but it wouldn't launch either. Would just be fishtailing with tire spin. I would have thought that the system was sophisticated enough to monitor tire spin/clutch slippage to get it "right" on the launch. So less throttle until the tires hook - but not cut out completely.

Is anyone else having a launch control issue with the cold weather?

 

Tried it last night - 64 degrees. Worked much better. I noticed that the impressive quarter mile times are being run in warm weather. I think the power gained in cold weather is not enough to overcome the poor grip caused from cold temps. Summer tires get hard and slide, so they don't grab on launch. Winter rubber has a much softer compound, but the l/c is so violent, that the pliable rubber (with less pure tread surface than a comparable summer tire) cannot put enough contact patch to the ground. So the winters won't go up in smoke from an idle launch, but won't give you great launches either.

I will put my summers on for my Atco rental in December and just hope I can figure out how to get them hot enough. Was easy to smoke up my E55 rears. Don't know how I can do a burnout with an AWD car.

Be interesting to see if any other 991 TT or TTS owners are having success at the strip on summer rubber on cold days.

If anyone thinks I am wrong/crazy - please chime in.

 

OP--what kind of tires are you running? did you swap wheels too? do you have centerloks? Tirerack.com search shows no recommendations for turbo S and dealers have shown no interest when I mention buying winters. It's depressingly cold already...will be a long wait.

There is a huge difference between winter performance tires and snow tires. In dry conditions winter performance are close to all seasons, not terrible.
But no sub 11 seconds 1/4 possible.

Do tracks just shut down when it's under 45 F rather than make tire allowances?