Shhh... don't tell The Frog

..

..

If my memory serves me right, and by all means, take this with a grain of salt, but this probably is due to being a square setup and the height of the tires in either the front or rear.. sidewall flex is probably the culprit, specifically in the back. Again, if my memory serves me right, your not losing traction, only the sidewalks flexing. Increasing the tire pressure in the back a few PSI above the front should resolve the issue......  And let me say again, take what I say with a grain of salt, it's been a good few years since I was versed enough in the handling Dynamics of the car to be confident of my word. 🙄 

..

The S.drives shouldn't be like that at all. Going 205 can make the steering lazy. Going with offsets that are not factory can also make the car more stable but also lazy and change the feel of the car.  Something that I warned you about that can change the dynamics of how the car use to handle.  

Adding more weight up front in terms of tire and wheel can also make the front suspension  not dampen as well as going with lighter components.  All of these changes has consequences that you can feel.  This is what happens when you try to gain a consensus  from internet opinions because there are a lot of people that cant tell the difference, what is acceptable to the way one persons drives is different than another  but the problem by far stems from  those that are  focused on appearance and the ability to rotate tires as their primary requirement so they double down on their choices. 

I do think your Issue  might actually be the damping.   I have test driven another Spyder yesterday for assessment that had S.drives and the problem wasn't the tires. It was the alignment and the suspension being blown out.  It could give the impression of the tires being funky but I can tell the difference and the car did not feel safe at all so I had to hold back because I did not get the feedback that was necessary to pound the car near the limits.  Just a little too scary and also the brakes needed to be bleed as it was squishy.  

I can tell you that the S.drives do not have the hardest side wall but they certainly dont have the weakest and is a good all-round tire as a good replacement with the least amount of compromises.  

..

Ok so I did some research for you. We assumed you previously had the Star Specs which are in the extreme category but now we find out its the DZ102 which is a different tire entirely. I would say its more or less in the same class as the S. drive however they have a reputation for having a soft sidewall.  The S.drives are somewhere in the middle of being acceptable sidewalls and generally a good all rounder and thats why they have been consistently popular because they fill more rolls with the least amount of compromise. 

Your problem could be not enough miles on the S.drives as they have a reputation for a longer break in.   Some tires like my Falkens dont take that long but the previous tires that I had taken at least 1500 miles before they stopped squirming.   

The S.drives are certainly not squishy. It has to be something else going on. I can tell you that the stock dampers blow out for any kind of performance driving  around 40k miles.  It will cause all sorts of issues that makes the car feel less confidence inspiring.  

..

..

...

There is no real way to know the softness of the tire and Tirerack is full reviewers that don't know tires.  I usually check the autoX forums as they are more reliable on foruming a consensus of tire stiffness and are usually spot on if something is clearly soft.  

Also there is a much more hidden information about tires that people have no idea one of which is the identical tire that comes with the vehicle from the factory is different that the one sold as replacements from a place like Tirerack if it is a general tire and not a vehicle specific tire  

I have been called out on presenting this fact because it seems ludicrous but it isn't.   The manufacture works with the tire company and makes one of their general tires match the engineering science that goes into each car. They actually change the formulations of the rubber or the construction.  Usually it will be indicated as a code.  

..

You cant infer stiffer sidewalls from the tread rating for a compound being soft sticky.  There is a lot more to it particularly the construction of the tire belts.  If this were true my tires should be supper soft but in actuality they are somewhat stiff but also soft compound wise that you can make a nice finger nail indentation when brand new.  

There is only one exception to this rule and that is tires that are designated RFT run flats  because they have to have a robust construction and therefor one of the side effects is a very stiff sidewall. However it comes at a great cost of not being able to fix a puncture and the tires are very heavy and expensive.  Its a one trick pony for stupid  people but may have some benefit from escaping an axe murder if you have a flat tire situation in the middle of the night.  

..

Here is another interesting thing about tires that people will not understand and will make assumptions including people in the quick tire change industry. 

 Some tires are labeled XL or R for reinforced.  Generally these tires  are lower profile tires.   When people read reinforced they think they made the tire stronger but in actuality the tires are weaker.  They do not reinforce the tires to make them stronger, they reinforce the tires to handled more air pressure. 

 It is not the tire that supports the cars weight, it is the air.   This concept screws with a persons  understanding and thats when mistakes happen because you generally need to add more air pressure for these tires to match the load rating and if you don't you will damage your tires. 

The most extreme examples are those that mix and match tires, those that use expired tires and  those that run the tires down to the wear bars.  A majority of the time assumptions are made rather than understanding that they need to follow guidelines even if they don't understand them.