Yesterday I got the tires fitted to the ARC-8's and today I put them on the car and went for a test drive.
It will surprise no one that this setup is a huge improvement over 19s with old RE050A's. The first few minutes of driving were weird, it felt like I'd lost a bunch of road sensation and it took a few minutes to realize it was just harshness and unhelpful noise that was missing. All the useful feel of the car and the road through the seat and wheel was still there, it was just a quieter smoother ride with much less of the unnecessary hum, buzz, fizz, whatever you want to call it. As soon as I realised I could still read the road as before I settled in and started comparing the difference.
I can't talk to how the Potenza Sports compare to the PS4Ss, but compared to old RE050A's they are very significantly quieter, I first noticed this by noticing that the CSL intake sounded louder! 18inch wheels are clearly what this car was designed for and are better than 19s in every way when it comes to ride quality and feel. I'm very happy I opted for the firmer sidewall of the Potenza's over the, softer than PS4S, PS5's. The accuracy and immediacy of handling is still there, significantly improved upon with new sticky tires. I need to give a big shout out to Bry5on for his advice to put 9in wheels up front with the ET42 offset. I'd always been worried about putting anything too wide up front, afraid of ending up with heavy, dull steering, but with pretty much the correct offset and lighter wheels and tires all the precision and immediacy is still there, and when you get on to windy open road the feel of the car with a larger tread patch up front and closer to square setup overall is just superb.
On the topic of weight. The combination of lighter wheels and lighter tires means I'm almost 4kg lighter per corner, which (including weight of the rotors) is close to a 14% reduction in rotating mass, and I can really notice the difference. I'm always skeptical of my butt-dyno because I'm always concerned it is excessively influenced by the "wallet factor". But in this case there is no doubt. Acceleration and braking both noticeably benefit, not to mention how much better the car ride and holds to the road with less unsprung mass.
In summary, as you would expect, this is a fantastic upgrade in every way.
I do want to thank everyone who took their time to give me advice and suggestions on this project. It wasn't one I was planning to do right now, and as a result I had not performed my usual excessive amount of research and preparation well in advance. I'm very grateful to everyone who shared their knowledge and experience to help me arrive at the ideal outcome. Thank you!
Like heinzboehmer I've very much missed driving the car while it's been laid up, so like him when I got it back on the road a short test drive turned into a longer one. Only I ended up at a slightly less globally-famous landmark. The Mt Rex sand processing facility in Helensville 😂 Also, it's winter here, it was raining, and the sun was in the wrong place.