Thanks Elevens -- Using this calculator http://www.venommotorsports.com/libr...calculator.asp which by the way is whacked for Tire & Wheel Inboard and Outboard increase saying 1.223 and 1.066 inches respectively (Not) says Speedometer Error% is -2 and that for an old actual speed of 70 the new actual speed is 69 with Engine RPMs of 2324 and 2372 which seems about right to me.