im no expert with metals but it appears the metal is too thin or brittle causing fatigue on the HR's.
if you use lug-centric aftermarket wheels you are minimizing the burden on that lip so you will probably not experience this ever. ive had Kics for 6yrs or so, never had a problem on both lug-centric and hub-centric wheel applications. i also have a pair of Eibach 20mm which are doing okay the last 3k miles of use.
