gungrave

I am getting kumho's ecsta spt for my wheels, but don't know what size to go with? should i go with 235/40/18 or 245/40/18's? my wheels are 18x8 by the way.

Turbonut

iTrader: (1)

I'd buy 245/40-18 which are around 25.5/25.7" in diameter.
I'd also look into the Yokohama W4S if an UHP all season is preferrred.
The W4S tire in 245 has one of the widest treads available at 9.2", compared to a Brudgestone 960 at only 8.2". Great tire for only $146.

-sNaFu*

Ideally, you'd want the 235/40/18. Diameter Difference is only 0.32% from stock. Diameter Difference for 245/40/18 is 1.52% from stock.

-JoEL*

Turbonut

iTrader: (1)

I'll add that a direct replacement for the OE tires are 245/45-17 which are 25.7". Stay with the 245/40-18 for a slightly better ride and pothole protection with a larger sidewall. It will also fill the wheelwell slightly, unless you like the rollerskate look with small diameter tires.
Your choice as both are appropriate with the 8" wide rim.

sparky57

I've been using 245/40s on my 18" wheels since day one. The slightly wider sidewall has saved the wheels on more than one occasion. No clearance issues at all even with the lowered A spec suspension.

rw

lusid

Related matter, do you change tire pressure as you increase from 235 to 245? or can you keep it the same, all other numbers are the same.

Also, I did a similar move with the week, went from 235 to 245, and noticed a less harsh ride. Thats my observation while driving on my 960's for only a few days.

sparky57

I started using the 39/36 recommendation but now use 38/36. The streets around me are a bit uneven and the additional nudge towards oversteer makes the fronts track the undulations too well.

rw