I don't think a soft sidewall would cause it to sway this bad.

I only replaced the rears. The fronts are still stock s02s, because they still have plenty of tread. I've done this before on other cars and never had any problems having different brand front/rear tires.

 

is that the recommended tire pressure

 

Just try adding like 2 psi to compensate for the softer sidewall. Its probably just flexing a bit

 

OEM 225/50-16 S02's have a wide tread width measurement, but the section width is pretty much the same as other 225's. Bridgestone requires rim widths of 6 - 8" for this tire, which is a typical rim width range for other 225/50-16 tires. AP1 rear wheel width is appropriately near the maximum rim width for this tire size, a little bit less. Pretty much "just right".

245/45-16 tires are (generally) designed for 7.5" - 9" wide rims. The stock AP1 rear rim is at the bare minimum width allowed for this tire size. So the tire is pinched a bit. Less than ideal for lateral stability.

 

It's also worth mentioning that brand new tires with full tread depth will have a lot more tread squirminess than worn tires, so that could be part of the perceived problem here.

 

Had the tire pressure checked and they were both at 33psi. Also had the wheels rebalanced. Haven't had a chance to take it on the highway, but I will update when I do to see if its still doing it. If yes, I will get an alignment.

 

Full tire tread always feel squirmy to me, then I get used to it, and it imperceptably improves as the tread wears down, then it pops up again with new tires - the circle of life

 

I went to 255 to 245 on the rear on 18's

Benefits
The tire now sits a little rounder on the rim and not so square. therefore I Have a little more tire surface grip.
Tire will wear a little less on the inside.

Negative side.
I notice the back is a little happier than before.
My current tires. Not sure if because the size or the wall softness (hankook ventus) did not protect my wheel on a very stupid pot hole damaging the wheel lip.
This didn't happen on my previous tires (falkens)


I will switch back to 255 on the next tire change.

 

watch out crazy lady attack in this thread - a stock tire isnt a 245 width and it's not comparable to any other tires stated specs. different tires are different tires / end

the ra1 is a lightweight circuit spec dot legal tire that uses fiberglass for reinforcement on many models in lieu of or in a addition to steel, it likes high static camber to perform due to it's profile and tread pattern - over 2 degrees negative on a civic and I'd imagine 3 degrees at least on the s2000 and it's one of the few tires that last longer and perform better when you shave off half there tread. Also it tends to be a little more giving to survive under heavy track use.

What your probably experiencing is too much sidewall flex, too little camber. Yes it's too wide for a 7.5inch wheel you can add some psi,more camber and shave the tread to 4/32nds to fix it or go with a 225 size.