Hi Katana, the reason most arbors only have flanges on one side is that is all that is required. The flange is just to keep the wheel centered on the arbor. The tightening nut is to keep the wheel flush against the clamping half of the arbor, and the nut only should need to be snug tight. The 3 different step flanges on our arbor allow you to true both front & rear without switching arbors plus it will work for 1/10 pan car rears as well. The steps in the flanges are machined to fight tightly inside the bearing opening and the rear wheel opening. Machining a step on the tightening nut could be done but it would eliminate using the same arbor on both front and rear.
Hope this helps.
Bruce Triplett
NEW:
RC4LESS 1/12 FOAMS
www.rc4less.com