Why not take a front wheel off and take it to the place where you are having the spacer made. The bolt pattern is the same front and back. The reason I suggest taking a front wheel to the person making the spacer as the front wheel is the offset is less and also if your rear tires are loaded you do not fight the weight of the ballast until you have to put on the spacers. JUst make sure that you measure the outer diameter of the rear hub.Does anyone know what the Rear Wheel Bolt Pattern is for the 2305? I tried measuring mine but I don't trust my results enough to tell someone who is going to make a set and charge me $$$. I have googled it and looked at lots of charts but never came up with a definitive answer.