lt1chevelle
05-24-2007, 03:10 PM
i see some cars running a 45 series tire up front and a 40 out back why is this? should i run a 235-45-17 up front and a 255-40-17 out back>
Ralph LoGrasso
05-24-2007, 05:39 PM
Keep in mind that the number is just an aspect ratio. Using your examples, 45 is 45% of 235mm, 40 is 40% of 255mm. The reason you see different numbers front and back is due to the wider tires having lower aspect ratios to maintain the same overall diamater as the thinner tires.
Josh69
05-25-2007, 06:07 AM
What Ralph said.
Most tire mfgr's will have a chart on their site, including Discount Tire or Tire Rack's sites that will show the overall diameters for a specific tire...that's the number to keep an eye on once you decide how wide you need to go. This will keep your front and rear tires close in diameter. For most cars I've owned, I try to keep it less than .25". It'll be different for drag racers, but for performance handling cars, that's my goal.