i have an 04 civic ex with yoko es100's. put them on and ran stock tire pressure with great handling and wear but one little problem. my fuel mileage dropped off to 28-30. used to be able toget 30-36. i know the rim is larger but they are motegi tracklites and only weigh 14.5 pounds,little more than stock. wondering if i should up the pressures and to what psi for a car of my weight and weight distribution. oh they are 225/45/17

 

The way to find proper pressure for a street vehicle is to use a big piece of chalk and mark across the tread. Thendrive the vehicle a few feet in a straight lineand check for even wear. Adjust accordingly.On an offroad vehicle you'd typically want to let out just enough air that the tread can conform to the terrain or provide max flotationwhile still supporting the weight of the vehicle. On a racing vehicle, you'd likely want to start with the highest pressure the tires are rated for, as the sidewalls wil "roll" during cornering. Running max pressure will generally keep sidewall deflection toa minimum.

 

If you ment the stock pressure of your stock tires,put in the tire pressure is says on the sidewall of the new tires.

I dont think it will make a difference though. I never noticed a drop in gas mileage when I put my rims on.

 

maybe the overall diameter of your tires is far bigger than the stock ones. I believe there is a computer box that calculates the optimum gas-air mixture taking into consideration your speed and rotation of tires. If you go beyond 3% of the orig, your mileage will drop. I heard this in yarisworld forums.