Michelin S12 Rear Sizing ?

So I'm looking to switch out my 606's for something more aggressive. I hear lots of good things about Michelin S12's and I'd like to try a set but I'm not 100% on which size rear to go with, especially with Michelin's funky sizing.

There are three size options to choose from and I'm debating on which one to go with. Not only am I after a tire that has better traction on sandy / muddy rooted single track but also lighter and smaller diameter (Dunlop 606 120/90-18 is 26.80" diameter).

I'm leaning towards the smallest size option for tire weight and diameter reduction so I guess I'm just wondering if the slightly narrower tire will make a noticeable difference in the sand.


Michelin size 120/90-18 (standard sizing 100/100-18), recommended for 2.15" rim , 25.86" static diameter

Michelin size 130/80-18 (standard sizing 110/100-18), recommended for 2.15" rim , 26.65" static diameter

Michelin size 140/80-18 (standard sizing 120/90-18), NOT recommended for 2.15" rim , 26.50" static diameter

I'd go with the top one listed (the equivalent to 100/100-18).