Tire size and Tuner/tranny adjustments

I just got a new set of tires: 285/75R/16 AT tires on my Chevy, an upgrade from the stock rubber. I have a superchips tuner which allows me to adjust the speedo for the tire size, but it reads in inches. Does anyone know how to convert the metric measurement to inches or would using a tape measure to get an average diameter from three angles be accurate?

 

I may be wrong, but I believe you would want to simply measure the exact height with a tape measure?

 

That's what I thought. When the tires were installed, the dealer told me that they were 32 1/2-33 inches in size, but when I measured them with a tape measure, they were about 31 1/2 or so, so I didn't know if there was a formula to convert the metric to inches. Then again, the dealer could have been wrong. I was also told by the Chevy dealer that the stock rims at stock height would fit 33's, and it looks like I'm right at that limit as far as clearance, so I'm confused....

 

there is a website with a conversion table on it www.4lo.com it will give you the info

 

I have been using 4lo.com for years for that stuff.

 

your a smaaaarrrt maan

 

Thanks!