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General Tire question - Issues on track

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Ok, I wanted to run this by everyone and see if anyone has had experience / discovered what may have caused this.

I have a 2012 boss 302, have run 18x10 wrapped in 305/680/18 DH slicks with no problem on track. I purchased a new set of wheels (18x10.5) and wrapped them in a different set of DH slick 305/680/18 which were purchased as scrubs from e-bay with "4 heat cycles". To be fair, the tires were quite sticky at VIR this past week, so I want to believe they are low use tires.

The issue arose as the car climbs to 120+ mph, it begins to feel unstable... the car wants to pull left or right and track what feels like 5+ feet from one side to the other. This isn't a great sensation going up the hill at VIR. It was so unnerving that during my session I kept it below 130 as it was simply too sketchy. I brought the car in, inspected everything at the on site speed shop (put it up on a lift). No issues with the car, took it back out and had the same issues. It seemed to be worse as I increased the speed and would feel as if the car wanted to come around under hard brakes. I came back in... I sat, thinking about what I had changed since my last time out and decided the only difference was the tire / wheel setup. I swapped my new 18x10.5 wheels and tires for my other set of 18x10 with the same size DH slick (these and proven to be great at Mid ohio just a month or two back).
I head out for the next run, as I climb up to 130 the car feels great... pushed it all the way up into the 145+ range no problem! No more issues whatsoever...

So, I clearly, it is an issue with these tires (or one of them)... but if they are VERY sticky and look to be in good shape, could there be something wrong inside the tires (belts etc... I don't know) and has anyone dealt with this before? I would love to find a way to determine which tire is causing the issue but I doubt something like a balance machine is going to help as all 4 tires balanced perfectly and there were no shakes or vibrations... rather the entire car wanted to move left to right.

Thoughts?
 
1,246
1,243
In the V6L
Ok, I wanted to run this by everyone and see if anyone has had experience / discovered what may have caused this.

I have a 2012 boss 302, have run 18x10 wrapped in 305/680/18 DH slicks with no problem on track. I purchased a new set of wheels (18x10.5) and wrapped them in a different set of DH slick 305/680/18 which were purchased as scrubs from e-bay with "4 heat cycles". To be fair, the tires were quite sticky at VIR this past week, so I want to believe they are low use tires.

The issue arose as the car climbs to 120+ mph, it begins to feel unstable... the car wants to pull left or right and track what feels like 5+ feet from one side to the other. This isn't a great sensation going up the hill at VIR. It was so unnerving that during my session I kept it below 130 as it was simply too sketchy. I brought the car in, inspected everything at the on site speed shop (put it up on a lift). No issues with the car, took it back out and had the same issues. It seemed to be worse as I increased the speed and would feel as if the car wanted to come around under hard brakes. I came back in... I sat, thinking about what I had changed since my last time out and decided the only difference was the tire / wheel setup. I swapped my new 18x10.5 wheels and tires for my other set of 18x10 with the same size DH slick (these and proven to be great at Mid ohio just a month or two back).
I head out for the next run, as I climb up to 130 the car feels great... pushed it all the way up into the 145+ range no problem! No more issues whatsoever...

So, I clearly, it is an issue with these tires (or one of them)... but if they are VERY sticky and look to be in good shape, could there be something wrong inside the tires (belts etc... I don't know) and has anyone dealt with this before? I would love to find a way to determine which tire is causing the issue but I doubt something like a balance machine is going to help as all 4 tires balanced perfectly and there were no shakes or vibrations... rather the entire car wanted to move left to right.

Thoughts?
Well, I had a very similar situation back on Oct 6th at a track day at Area 27. I was in my 2016 GT350 Track Pack with four MPSC2's - the fronts had 3 track days on them and the rears had 7. On the 260 mile drive to the track the rear end of the car started twitching occasionally at 60MPH going around gentle right bends on otherwise clear pavement. It felt like something was loose, so I stopped and checked the lug nuts and rocked the wheels, but all was well. At the track, grip was great and I turned in a PB, but at the end of my last session the car did exactly what you said - about 2/3 of the way down the long straight, I was still accelerating at 120 MPH when the rear end took over and steered the car to the left. By the time I'd straightened it out, I was about a car width left of the line I wanted to be on. I slowed it down, did a cool down lap and the day was over. I was sure I had a suspension or ABS problem but the car's fine now with different tires on it and the rear alignment remains exactly where it should be. By mile 200 on the drive home, though, the back end was doing the lateral twitch so much my arms were sore from counter-steering.

I don't know what the problem was - the tires were end of life anyway so they've been recycled already. I'll start next season with a complete check of the rear suspension and an alignment, but for now I think it was the tires.
 
713
69
I drive a 12 Boss also and I've experienced the same thing at NJMP Lightening. Coming out of the bowl with slicks only. For those that don't know the track. It's a high speed banked turn leading into the main straight. It happened on the main straight and I thought I was going into the pit lane wall. That was scary! And the guy behind me was lucky to catch it on video for me.


Usually I keep the traction control in sport mode. But last time I turned it off completely and it did the same thing.
I'm debating changing the ABS module.

Sent from my SM-N950U using Tapatalk
 
I actually run the 302S module, so no TCS / Stability and aggressive ABS. Idk if that matters / helps. The car felt like it was pulling slightly to the left when I had those slicks on as well... I could actually tell when I drove it on the street for a short stint (just got get gas).
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
I drive a 12 Boss also and I've experienced the same thing at NJMP Lightening. Coming out of the bowl with slicks only. For those that don't know the track. It's a high speed banked turn leading into the main straight. It happened on the main straight and I thought I was going into the pit lane wall. That was scary! And the guy behind me was lucky to catch it on video for me.


Usually I keep the traction control in sport mode. But last time I turned it off completely and it did the same thing.
I'm debating changing the ABS module.
I'm familiar with NJMP/Lightning.

I saw the Pontiac (Don?) pass you in the bowl, and it looked like you had backed off there and were way up high. It wasn't until I watched the mirror that I saw a car suddenly head for the pit lane wall.

Were you upshifting?


Norm
 
713
69
Hello Norm,

Yes that was Don in the Pontiac. I didn't back off in the bowl, that was the traction control intervening. It does that once in awhile in the bowl. Only with the slicks.

And yes i was up shifting. The whole rear end of the car just shifted to the left, which pointed me towards the pit wall. Definitely a pucker moment. I over corrected and was headed off track, and then traction control kicked in and I corrected to go straight.

Then a few sessions later I locked up the wheels and destroyed the slicks.

Sent from my SM-N950U using Tapatalk
 

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