Yep, I hear you. I spent some time researching it. Here is a link to an aftermarket lug nut with the shoulder on it, for future reference. Dorman 611207. It turns out that my stock lug nuts are two piece with a cone that spins on the nut. They seem to work ok for holding the cap on. However, my caps are from a Crown Vic Police Interceptor which has a 114mm bolt circle. So I had the bend the tabs down to the 108mm. They seem to be staying on. There are a couple of guys on the Focus forum that are running them. I'm not sure if they would work with the Ranger caps you have pictured. Your spikes are definitely cool, but I would probably hurt myself on them!