I don't think you would have to remove the tire. The only reson that I can think of that you would, is if you want the plate reloctor on the opposite side of where the nut currently is. If so, then you would have to pull the axle through and turn it around. If you don't need to do that, then I believe if you remove the cotter pin and the nut, you should be able to slide the spacer off, replace with the plate relocator and reinstall the nut and cotter pin. You might have to loosen the chani to remove the spacer, and if so, you'll have to tighten it again when you are through. Having said that, I may be missing a step, so you may want to wait until some of the more experienced wrenches answer up.