Even on my 8.5" rims the 245/40r18 ( 98mm side wall )has more movement on the rim on turn in than the 235/35r19 ( 82mm side wall ) ,but on some local B grade twisty roads I've noticed the 245/40 seems to keep more contact on the road compared to the 235/35 which felt like it was skipping sideways more . Either way I need to get more k's up on the twisty's .
A 245/40r18 on a 9" rim is probably the best option ?
Cheers
How many miles on your PS4S? Michelins seem extra squirmy the first 500 miles or so. I always feel like I made the wrong choice until they get worn in and then they feel good.
Yeah bentin, that was >90% of what I was noticing and attributing to tire sidewall spread. It was just that the tires were not scrubbed in yet. Now that I have about 500mi on them, they stick like glue. The 245/40-18 on 8" wheel definitely does lose just a tick of initial precision over the stock 235/35-19, only noticeable in like a tight round-about that you are going straight through where you are right/left/right very quickly, overall grip is better, especially on real roads with irregular surface. In addition to more rubber on the road, its doing a better job of micro suspension (conforming to road surface) to not get upset. Its a street car, so that tiny bit of precision lost is negligible.
The ride is so much better with more air volume in tire. Even though on paper is is just a bit more sidewall, and a bit more width, the tire casing at tread is at least 20mm thick(at least new), so instead of 82mm to 98mm, its more like 62mm to 78mm (roughly, just to illustrate % increased air volume is greater)... and sidewalls are at least 10mm thick each so its more like going from 215 to 225 internally. Point is if you think about the inside volume increase its bigger than you would initially consider based on external size delta, which explains at least to me, why the ride improvement is more than 20% better, it feels >40% better.
I keep the suspension in sport settings now even over rough roads. How much of that is just 235/35-19 vs 245/40-18 on 8" wheel, and how much of that is Conti 5SP vs Mich PS4, I don't know. But I am very happy with the result.