I've never heard anyone describe the vibration at 55 mph in their 37's as a "very suttle rhythmic vibration"
Most are just trying to get them semi-balanced for road use. I don't have any experience with your brand or size.
Sounds like you got a good set of tires.
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They are good tires(toyo oc). The vibration does not shake anything, and no one else but me would notice. Weird.