Originally Posted by JCL

I would take the stock rims as being the correct (design) offset. Applying any spacer generally changes that away from the optimum rim location.

Aftermarket rims should have the same offset when they are selected. If they are wider, there is a portion of that on the inside, and the rest on the outside, but the offset is the same. Said another way, a two inch wider tire only looks one inch wider from the side, you have to crouch down behind the vehicle to see the total effect of the wider tires.

If you have aftermarket rims that have less (ie incorrect) offset then the appropriate spacer can be used to bring the wheel back to the proper location. In that case the spacer is a good thing from an offset/wheel bearing life standpoint, but still possibly a negative on the new failure mode due to the added shear plane.

What the fans of the TUV certification are not acknowledging is that while a hub centric spacer is better than a loose spacer, it is designed to bring a wheel with the wrong offset back to the correct location. TUV would like that. TUV aren't regulating whether people are using the spacer for that purpose, and in fact people seem to be claiming that the TUV certification somehow supports running incorrect offsets, which doesn't seem right to me.