Why do rigs have their front wheel rims sticking out while other rims stick in? http://www.discountramps.com/truck-wheel-risers-1.jpg My first theory was that it allowed them to use a common axle length for all axles on a rig but subsequent observation reveals that that's not the truth. Front wheels and rear wheel are flush with the sides of the vehicle, meaning that the rear axles must be shorter (see diagram 1). My second theory has to do with making room for the steering/pivoting bearing (which is unique to the front wheels). Having the rim stick way out allows the mechanism, and most importantly the actual pivot point, to be vertically over the contact point on the road (see diagram 2). Am I close?