hi all,could somebody give me the website on tire circum. so i can recalibrate my speedometer with my edge.im 5mph off after putting on 285,s.thanks,bill

 

The instructions are in your manual, but 1010 Tires.com has a calculator displaying close to accurate mm sizes.

 

Not sure which speedo is 5 mph off, but keep in mind that the truck is always about 2 mph fast at 60 mph. That is just the way Ford builds them.

As stated, the formula is in the manual, but they fail to allow for 3% to 5% squish factor. What ever number you get, deduct at least 3% of it.