This sounds like "Snap Oversteer" which is usually a driver technique, and will improve with a bit of experience.
I experienced it the first time I tested the Mustang on the track, trying to find the reaction of the Mustang [which is very different from my Corvette]
It is usually caused by getting off the brakes too early while still OFF the throttle.
When you get off the brakes, the car will turn in nicely. But the rear wheels are still "engine braking" so it snaps around. If you row down the gears it can make it worse.
Try and not "push the car to it's limit" but instead concentrate on being smooth. Your lap times may get slower initially but then will get faster.
Your tyre pressures are probably OK because the other end of your car is behaving itself [I'm at 38psi all round, but on a race tyre]
Are you saying it could be pilot error?
I don't dispute that, but I'm pretty consistent, if nothing else. And what's that saying... smooth is fast, fast is smooth. I try to adhere to that; learned that with motorcycles years ago.
I didn't lift; I was on the gas, though not hard.
"Using all the track." This does not apply 100% to every single corner, but it will apply to probably 90-95% of all corners out there, but basically once you hit the apex of a corner you should start opening the wheel and feeding throttle. If you keep the wheel turned after the apex of a corner the car will have more tendency to oversteer as throttle is applied.
This is a video our driving school likes to show, and it explains it very well. The "spin" happens right at :35.
1. Notice he didnt open the wheel up and go to the far (left) side of the track after the corner like the camera car did, he kept the wheel turned and stayed more in the middle.
2. The wheel was still turned while power was being applied, and the car oversteered.
It happens to all of us, just something to be aware of.
https://www.youtube.com/watch?v=7iCClUNg46c
Spectacular! The first part, where the tail got loose, was similar to what I experienced, but I didn't put on nearly as good a show; caught it and continued. I think I still had some steering lock in - turning right - because there's a right bend in the track before the next turn.
Thanks for explaining tracking out, BTW.
Do you remember being either a bit late and a bit too sharply getting out of the brakes or a bit early/greedy about getting into the throttle? Anything else different?
Do you remember anything about the same turn on the preceding lap or two?
Norm
Same every time, though the tires were definitely getting greasier.
OP, as you can see there are a lot of possibilities.
In terms of basic car setup, and at the risk of over-simplifying, anything you can do to increase rear grip or decrease rear roll stiffness should generally reduce oversteer.
As someone said, your PSI doesn't seem way out of whack.
In terms of technique, it seems a good guess you either may have been doing too many things at once, for example, too much steering input combined with too much gas, or you may have been doing things too abruptly.
There are a lot of good resources to geek out on this stuff but I've found the attached to be pretty well written and comprehensive. Look at Lessons 4 and 5 and see if you recognize anything you might be doing:
https://driver61.com/uni/
Thanks for this. I'll actually go through a number of the lessons. Need to sit down and focus, which I couldn't do today.
If the car has a stock diff (which if it does, is probably worn out), could the rear tires be getting overheated before the fronts because of being spun up on corner exit?
Front and rear tire pressures increased by the same amount over cold readings. It still has a TrakLoc, but I don't abuse this thing, and it only has 53K miles on it. Realizing its limitations, works as well as it ever has.
In my mind, that is possible, but not as likely as the fact that the car is just under-tired. 255 all seasons on a mustang is not a recipe for success.
I remember when 255s were HUGE. G60s, for my fellow old-timers.
That for sure, the wheel & tire combo is way too small for track day use as the OP is finding out!
Seems to be the consensus.
I think in order for that to happen, the OP would definitely notice his 1-wheel burnouts.
Though I will agree that your stock TracLock is basically an open diff at this point.
See above. I don't think so. I know you really like your Eaton, though; may have to kick down for one of those, or a Torsen, in the future.
Correct PSI should be determined by tire temperatures and wear, at least partially. Setup has some to do with it as well but since you can't easily change camber (with strut mount plates) it's a bit less important here.
IMO what happened sounds like a technique problem, not a tire pressure problem.
Could well be. I didn't do anything different on that lap, which is why it surprised me.
I'd like to know more about the car's behavior at other turns on the track. Any similar tendencies elsewhere? An abrupt change in front to rear traction balance might be due to some track-surface characteristic you missed by six inches on all the other laps.
Dunno. I remember you're a CA guy... have you done Thunderhill? It was turn 9 on the short track. I didn't have any issues elsewhere on the track. FWIW, that's the only "tight" right-hander.