Here is a good example why _this_ collars could be theoretically beneficial. There was quite a misalignment on some holes between the body and the subframe. That will most likely lead to slightly asymmetrical caster/camber. Collars will in theory align them, which is good. Still, I don't see any possible "structural" stiffening coming from them, as they do not reach deep enough in the subframe holes and shoulder does not go in between the body and the subframe. And the torque on this bolts would not allow any body-subframe movements without any collars anyway.
Or we install them the wrong way and the shoulder should go in between.
Would I make them myself for this alignment purpose - they would be just steel or stainless sleeves without any shoulders, that are long enough to reach almost all the way through the subframe in order to register it at the bolt tip, not the head.
Or we install them the wrong way and the shoulder should go in between.
Would I make them myself for this alignment purpose - they would be just steel or stainless sleeves without any shoulders, that are long enough to reach almost all the way through the subframe in order to register it at the bolt tip, not the head.