The other day I started thinking about buying tires for my Nissan Altima. Try these tires for nissan altima on this website for quality tires. Here are quality reviews and truthful reviews. I myself have used this site, I advise you too. I also advise you to look through all the available offers and choose the most suitable tires for your climate and weather conditions.
To find the exact answer to your question, use the AThingForCars Tire size chart. On this resource I learned how tall is a 285 60R18 tire athingforcars.com/tire-sizes/285-60r18 and thanks to this I was able to make the right choice
You will go from having a 7.3 inch side wall to a 3.6 inch side wall. The diameter of your tire will be 7.4 inches smaller. Your over all circumference will be significantly smaller requiring additional rotations of your tires, this will throw off your speedometer. It will say you are going faster than you actually are. Layman’s terms, your speedometer will be significantly off. The reduced side wall will make for a significantly roughfer ride. The side wall is the largest shock absorber in your car.