If you can't see those 1 cm tall spikes, you need to go a doctor. I need solution not sarcasm. I'm sure you can't say that that's normal thing. In this video you won't need glasses: This is still a problem. I hope that new CPU will solve this, but no one could say that this is 100% because of the CPU.
Have you also tried this with only official content? GT3 at silverstone for example? I've tried to replicate this without succes, I didnt see any framespike.
Crash the car in practice, that should load all the extra bits into the cache. Going back to the F1 2k days, we used to use the first practice lap and continually look around as you drove the lap. This stores as many of the enviroment textures as possible, also explore the edges of the track to load all the various sounds for curbing, sand, grass etc. Stuff the cache with as many trackside objects and sounds as possible.