Looks like it breaks right where the step is cut for the centering of the wheel. Is it a sharp 90 deree cut into the corner of that cut? If there isnt a nice radiused smooth transition that is a major stress riser spot. Always used to break axles on circle track car running stock axles. Same type of deal sharp edge and always broke there. Started smoothing and polishing that out with a die grinder and flap wheel and never had one fail after that. Crank shafts, same deal when grinding them. But also agree on the design and wheel dish. That is a insane amount of leverage. Kind of amazing there isnt more failures. After looking at our s78 i see they also have a step machined on the back side that is pry straight across from the one on the other side. Id be willing to bet this is what is leading to the problem.
Last edited by Smallchev; 10-16-2019 at 12:36 PM.