New BF Goodrich KO2's - True Diameter?

Yesterday I bought new BF Goodrich A/T KO2's, size 265/70R17, load class C. With the truck parked flat in my garage, tires cold at 34 PSI, and a level placed on top of the tread, I measured the height at 30.6". This is a full inch below what I would expect. For comparison, here is a photo of my old full size spare (265/70R16 with 100% tread) side by side my new tire. My new tire should be about one inch higher because I am now running 17" wheels... but they're the same height!

Has anyone else seen BF Goodrich tires run noticeably under size?

 

Wider wheel.. pulls the height down.

 

With the weight of the truck being on the tire would bring it down

 

The only thing that changed is the size of the wheel...the tire size is the same. More wheel inside of the tire now is all. At least that's what I take out of this. They're both 265/70 so why would one be bigger than the other?

 

265/70/16=265/65/17 265/75/16=265/70/17

 

So much wrong in this thread

 

265=width in mm, 70=aspect ratio. That's the sidewall height compared to the width. So it's 70% of 265, Which is a 185.5mm sidewall. So to find tire height it would be 185.5mm+17" wheel+185.5mm. That's why a 265/70r17 would be taller than a 265/70r16.

 

I went from the same, to the same. The new ones are definitely taller. Threw my speedo off a bit too even after I did the recalibration through my head unit.

 

This. BFG specs for the KO2 diameter in 265/70r17 is 31.7" so about an 1" lost due to vehicle weight. If you look at your tire from the side, you'll see the contact patch where the tire flattens out. If you wanna measure the tire, measure the diameter horizontally.
Also keep in mind that actual sizes will vary from brand to brand, and even vary on tire styles within a brand. And most are undersized.

 

Yeah I was figuring the height loss is due to tires being loaded.

 

How do I recalibrate my speedo? I've got a Tactrix OBDII. What software did you use?

 

Its deep in the headunit settings. I searched on here and found someones instructions. If you cant find it, lmk and I'll dig into my head unit again and see if I cant remember.