I found that out the hard way around 2000. For many years I didn't carry an extra spare for my trailers because I could use my spare from the pickup. It wasn't very long that I discovered that my 2000 GMC spare no longer fit 7k trailer axles. My cousin who is a gmc dealer told me they had gone to metric. I trade pickups every 3 years, but I think my 2000 still had regular hubcaps which covered the bolt patern. My 2012 has the plastic nut covers and it is real obvious that the bolt pattern is different.
