The Nissan Path

I have upped the aspect ratio to 70 on a pair of Michelin's (2012 Silver Edition).
They are probably the Defender LTX (I will check later; it is what my CostCo had).

The TL;DR? My Speedo is now correct with every GPS speed measuring device I can throw at it.

With the 265/65/r17, 70 MPH indicated was actually closer to 67.

I am nerdily giddy about this.

You only got a pair and not a set? I had a tire shop do that to my 2008 (they ordered the wrong size and didn't notice they were a different size than the front tires) and it kept activate the ABS every time the brake pedal was pressed!

Ack. Mis-typed.
Yes, I got 4. Thinking about dumping the spare to save weight.

I have same tires 265/70-R17 (BFG TA-KO2 and previously GY Duratracs) and found them to be dead on point real speed with tacho...
...but only when they were new. I think I've calculated approx. 3mm (1/8'') of tire wear increases tacho displayed speed for approx. 1 mph.