OK, I've done the measurements and here are the results. But first, allow me to document the process.
Here's the car involved:
It's a 2006 Mercury Milan. It has 215/60R16's on it (as opposed to the stock 205/60R16) inflated to 34 psi (33 placard pressure).
Here are the tools:
A jack, masking tape, tape measure (flat tape), safety pin, marker (sometimes called a Sharpie!)
I jacked up each tire on the driver's side, wrapped the tape around each tire using the safety pin to hold the tape onto the tire as the tire was rotated, and recorded the measurements.
Here are the measurements;
LF: 6' - 9" = 81"
LR: 6' - 10 1/8" = 82 1/8"
I then lowered the car onto the tires, marked each tire with a radial line on masking tape, positioned the tire so the tape down down and added a line on the ground at the point of contact.
OK, OK, my line isn't the best, but it doesn't matter as you will see in a moment.
Then I pushed the car back to get one rotation of each tire, then marked the ground again - followed by measuring between the 2 marked.
Results:
LF: 6' - 7 1/8" = 79 1/8" or 97.7%
LR: 6' - 8 1/8" = 80 1/8" or 97.6%
OK, so it isn't a 3% difference, but it's more than 2%!!