tire size for filling with rimguard 1510d

[Roonabeck]

So - Lets work up a rough estimate of height for an 8 x 18 rice tire. 18" for the rim. 8" rim-to-ground. (assuming 100% height/width). Another 8" above the rim. Total height 8 + 18 + 8 = 34" overall height. How close does this come to what you measured?

Pretty close. My 8-18s measure just over 32". New ones would probably be a bit bigger -- Hoye shows 33.1" Wheels & Tires (NEW!)