I can't remember the measurement, but I know that my R is 4" wider than my X was before I tore it down, and I love it. I'll pick up 2" with the aftermarket wheels so I'll try that first and see how it goes. If I don't like it I'll pick up some 1" spacers.
Jason
85 ATC 250R - restored stock other than 18" rears, nerf bars, Honda key switch, 14T front sprocket, and white tank and plastics (except rad shrouds)
87 ATC 200X - restored stock other than 18" rears and nerf bars
84 TRX 200 - rough but complete budget restore for wife and eventually daughters to bum around on
Eton Viper 50cc - oldest daughter's current ride