How to center back tire of harley davidson 2005 road king

If you have the spacers in the proper places, the rear wheel is where it should be as far as "centering" goes. Not all wheels are designed to be "centered". On a Softail, there is an offset but I'm not positive about your road king.

Now, if you're talking about the alignment of the rear wheel in the swing arm, the RK has the adjusters on the rear of the swing arms's arms. Measure each bolt and when you get the proper belt tension with both bolts being the same length, you're aligned. The way I do it is move the wheel forward until the belt is too loose. Then set the lenghts the same. Then by turning each bolt the same amount each time, I slowly bring the wheel to the rear until I get the correct belt tension.

Good Luck
Steve