Help please

[Joshg]

I just put new tires on my truck and they are bigger so I Need to change it in the programmer, I know how to change it and all that I just don't know what size my tires are in MM? I've read that there's a chart in the owners manual but I bought my gryphon used so I don't have the manual. So if someone could please help me out and give me the correct numbers to put in would be much appreciated, I asked for help on f150forum but got a bunch of smart remarks. My old tire size was 275/65/18 and my new size is 285/70/18. Thanks and plz no smart comments.