I have a 2007 with 3.73 rear gears. If I go from 265/70/17 tires to 285/70/17 tires will it raise my ratio or lower it. I am reading on here that it will take the ratio down to around 3.55 but this online calculator says it will go to 3.85. I used a tire Diameter of 31.7 for old tires and 32.7 for new tires. Any info would be great. Want to buy new tires this week. Pete

Here is the link to the page
http://www.currieenterprises.com/ces...omTireSize.htm

 

Are you sure that calculator isn't telling your what gear to put in it to make it act like a 3.73? I don't think it goes down to 3.55 but I could be wrong. My spedo read 23pm slower than actual and dropped 100 rpm across the range in 5th.

 

Not sure. Just found the calculator on line.

 

The effective ratio will be lower but don't think you are going to get to 3.55.

 

3.73 to a 3.43 (auto) you will drop 100 rpm at 75 mph. Do a little figuring around those numbers, then see where your at.