250-500cc 140/80 18 Rear for 2012 wr250??

I've been happy with the d606 Dunlops on my other 4 stroke 250 bikes.. The Michelin that came on my wr250 is pretty slippery in the north east sand. I went to order another set of d606's but they aren't even made in the 140/80 18 size.. max out at 130/80 18.. I noticed the Dunlop d908rr which is twice the price but the right size.. but it seems like everyone running those have huge cc bikes. Wondering if I can get away with a 120 or 130 width tire or if i should stick to the 140 width.. Any Suggestions on size or brand for that matter? I occasionally ride on pavement around town or to the trail head so i'd like to try and stay with a DOT tire..

I would run a 120

Either a 120 or 130 works fine, you won't notice the difference between a 130 and your current 140. I thought the original Michelin 140 was quite good - but only for about the first 60 miles then as it started to wear the grip was lost immediately. Also have a look at the profile of the tyre, you can see that although some tyres are 120 or 130 width the radius shape gives a large contact area which is great in mud and sand.