Since you have two sets of wheels, are the size/width/offsets the same? Including tire sizes? Maybe it's an alignment issue with the old set worn in and the new set more sensitive to the alignment being a bit off?

Check tire pressure too. Many tire shops over inflate to the max loading. 33/39 is a preferred setting for partially loaded (see the owners manual).

Same tire size. Wider offset on new wheels. Car aligned on new wheels and tires. Wider offset cause this??

So here is a real dumb question........are you sure the tire shop put the correct side of the tire on the correct side of the wheel? Crazier things have happened.

Not dumb and not crazy...they are OUTSIDE out. Made me look though!

One other factor, ambient air temps. My PSSs get very loose when the temp drops below 45F. In the winter I run Conti all seasons on Carrera Classic rims.

I'm curious about tire pressures as well. I run PSS at the track and they're solid as a rock at 115+

They seem to heat up pretty quick, even on a cool day. Pressure cold I start at 33/36 and once warm they easily get to 37/40. Which is where I always kept the PS2. Again, they handle turns great, just that wandering around at speed is kooky. And to throw the stock setup back on and have everything back to normal??

The offset difference would be like running 7/15 spacers, like a lot of guys do. So nothing too radical with the offsets, but the track is wider now.

I truly appreciate the conversation and input here. I'm not splitting hairs I promise. The first time I was out on them for a longer drive with a group in the country, I ran it up to about 115 briefly, one little gust of wind and the car moved like a foot. Scared the crap out of me. Wind or not, it's NEVER done anything like that. Since then I've been paying attention and it just starts floating around at 95. It's very smooth but the wheel feels light in my hand.

Try running 39 in the rear. They're so large, they don't heat up as much as the fronts (more surface area to radiate heat + no steering and less braking friction). I run 33/39 and I show 37/44 after a hard session and they feel perfect.

So you're saying start cold at 33/39?

OP... do you have 3rd radiator installed?

Yes, 33/39 cold

On start cold temp: The official 'Cold' temp reference means 68F. That is, if you use 33/37 those values should be set at 68F. If the actual cold temp is different, correct accordingly. For instance if the cold temp is 48F subtract 2PSI - set at 31/35.

This is the proper 'cold' reference thinking followed by PAG and leading tire manufacturers.

What's the formula for this? I'm a stickler for tire temps, and I run in a variety of ambient temps. Both DEs I've done with these new PSS' were similar temps (around 60f), so I don't have any idea what to set cold if I do a summer DE and the ambient is 100f.

Dude!!! HUGE improvement!! Wow...I had no idea what a difference a few pounds could make! Transformed the ride at high speed! Very stable up to 120 (just a quick burst)...ZERO weird feel. Still not as stiff obviously as the PS2, but that made a monumental difference. I never ran pressure that high in my PS2's so it never dawned on me to boost it that much. Temp set at 33/39 in the garage, probably 60 degrees ambient. Outside temps 51 degrees. I really drove it hard (on the tires) for about 45 min, temps settled at 36/43 to 37/44.

Thank you guys for sticking with this and helping me figure this out!

And...no 3rd radiator.

Glad to help!