The weather was a bit cooler than usual this afternoon (around 65F or so) and I have probably 35 - 40% tread left on the OEM MPSS. Entering a right hand turn, I did a shoulder check and saw some cars coming. I knew I had the power to accelerate and merge in easily. So, mid 90 degree turn, I decide to go full throttle (sport+/manual and TVD in slalom). As soon as I stomped the throttle mid-turn, the car screamed to redline and traction control light flashed like crazy as the tail slid out left as the car straightened out of the right turn. I did not let off the gas and simple unwind the steering as the tail came in line. As I straighten out full throttle, the tail now violently starts wagging left and right about 3 or 4 times before I get to redline and shift to 2nd then I was let off as I was far ahead of traffic.

Again, key was left/right wagging happened after I had straightened out and had come out of the turn and gained traction back and I was accelerating in a straight line.

It felt like the torque was rapidly shifting left and right. I don't remember if it happened exactly before the 2nd gear shift shock or after.

Wondering if anyone else has experienced it? Felt to me like it was the TVD messing around and doing funny stuff as I had traction at the time? Did anyone with LSD have seen it? My rear tire pressure is at 38 psi cold (around 39 psi warm) and rear end is very stiff so the wagging occurred rapidly both left and right. Put rapid left/right momentum together with the weight/mass on the rear axle (had a half tank of gas), you can get the picture that I got some whiplash left and right.

No big deal and it actually was kind of high adrenaline rush, but just curious.

 

Do you think it would have behaved differently if you had traction control off completely? Wouldn't your rear end simply try to get ahead of the front, causing you to spin out at that point at full throttle?

I've had a similar swooping right turn, where I was merging where I had a yield, so instead I stomped on the throttle (sport + with TVD set at Track, traction ON), and it just beautifully accelerated.

 

Your tires are probably 5 years old and age is just as bad as wear on a performance tire, in my opinion. Once I got rid of my old factory tires and put fresh rubber on, my car changed completely. My guess is all the control systems were fighting old tires.

 

That is the thing. Even though, the rear was rapidly was wagging side to side, at full throttle I always had the confidence the car will not completely spin out. It just felt rapidly the torque was shifting side to side. I kept it full throttle since I felt it will come out sooner if get maximum forward momentum. Regarding traction control off, I am not too sure since I never have driven without the traction control on. It probably would have been more difficult to control if the traction control was off. That would be my guess.


Yeah, that is definitely the most probable reason in mind. It was cooler yesterday around 60 F - 65 F. I keep around 39 psi hot on the rear so the cooler temperature and high psi made the rear end like a brick. Also, I had finished washing my car a little while earlier. The tires might have some dampness still in them. My tires are now almost done with probably 30% tread left. I think the TVD also was messing around with shifting torque rapidly side to side. Not sure if it was the "playful" tuning aspect of the TVD or it simply went crazy with the traction loss in the rear together with my steering inputs unwinding the steering as the rear was straightening out.

I am just winging it till end of October when I will put the car away for the winter till next year. Michelin Pilot Sport 4S (XL) are the first thing to on my list for April 2020.

 

Just a thought but in essence isn't TVD supposed to react like that.

I'm certainly no expert but you see that tail wagging behavior a lot with motorcycles. Generally
related to overall speed and some issue with front suspension.

With heavier bikes turns also seem to play a roll.

Wouldn't be surprised if several things were at play here including TVD.

 

Are you able to go out there and duplicate the situation? Or try it in a large empty parking lot and see if the behavior repeats itself? Would be interesting to monitor the torque distribution display through the turn as well.

 

It sounds like the TVD, traction control were doing what they're supposed to do except they were dealing with some bad tires? I wonder if it would have behaved the same if it was in TRACK mode? I have been in scenarios like that many times, but with cup 2 tires and always in TRACK mode, car hasn't exhibited the violent wagging described.

 

Your bike analogy is quite accurate as torque was shifting side to side, but the rear tires had traction. Front suspension is perfect. I knew exactly what the front was doing and knew as long as I steer it in the right direction, the rear will figure itself out. Just simply looked like torque bursts left and then right about 3 - 4 times. It steers perfectly and tracks straight during acceleration if I have fully 50/50 traction from the rear. Also, had my suspension inspected from the dealer a few months ago and the mechanic said there was no need for alignment until I get new tires.

Yeah, definitely the same road, I can replicate it as it is a fairly empty road most of the time and also cooler temperatures are becoming more normal as summer is over. I will try and do that in the next few days with my POV camera.

Yeah, that is the most plausible explanation. It simply felt like the TVD was doing something as it was rapid left and right torque bursts after I had gained traction. Cooler temperatures with bad tires and a freshly paved very smooth road must have all compounded the issue. It never happens in warm temperatures when the asphalt temperature is high.

 

You mention the road was freshly paved.

That was probably the cause of all this. Freshly paved roads leech oil products on the surface for a long time.

 

That is true. It was paved just about a week or so ago. Super smooth.

 

I've never had this problem, but I also only drive with traction control fully off, pcs off and tvd in track mode.

 

I have all of them on all the time and TVD in slalom mode. My tires are also near the end of life.

 

Sounds like oil on the roads causing this.

 

Yeah, it was a freshly paved road about a week ago. Very smooth, which is why I felt confident turning and burning before the traffic got close.