[sanddrag]

We typically guestimate to account for powder coat thickness, then add another 5 thou planned allowance (slop), then add another 20 thou or so per side with the anticipation of using a shimming washer between sprocket and bearing and between wheel and bearing. Also, it won't hurt anything if there's a little extra space between the grooves. If you want to get it just perfect, you can custom machine spacers to exact length to go between the wheels and bearings.