Matching tyres... or maybe not.

Having debated a bit on here recently about tyres, I decided to measure some of my own. I have a spare set of 4 x 16" Freelander alloys on that I bought from a friend who swapped them for 17" jobs a few months ago. The are shod with winter tyres, 2 x Pirelli Sottozero and 2 x Cooper Weather Master, all in 215 x 65 / 16 format. All are lightly worn with at least 6mm of tread on each, all at 30 psi. I used a dress makers tape measure and here are the results (in mm):

Pirelli #1 - 2175
Pirelli #2 - 2174
Cooper #1 - 2122
Cooper #2 - 2142

What a difference, even between two of the same tyre bought at the same time! If you kept the same make on each axle, you would see a over 2% difference in axle speeds, not good...

Richard