250-500cc 5.10-18 on a WR 300?

I'm currently running a Maxxis Des. IT in 120/100-18. How much different would a 5.10-18 IRC VE 33 be? Any opinions on this particular tire?

A 120 is 4.72" wide. The Maxxis is a beefy tire and I run it as well. I would bet its true width is a little wider. The IRC is obviously a bit wider still. I'd be willing to bet you have the width clearance in the back. The stock tire is a 140, which is technicall 5.5" wide. However, I think that the stocker was a "narrow" 140...it is still a fat tire.
As far as the actual tire goes...I know nothing... Ha!

Love the Maxxis Desert IT on the rear of the WR360...l can run the thing down to 8psi without pinching the tube.

PS. Have no idea when it comes to imperial measurements of tyres....l just go by 120/100 and 80/100

After more research....Maxxis lists the Des. IT at 5.3 inches wide and 27.5 high. The Irc is 5.07 wide and 27.4 high. I still would be interested in any reviews on the VE33!