According to a salesperson at OK Tire (tire specialty shop), there are 3 tire specs.
Ordering from manufacturer direct (like they do) and dealerships get A spec. Which is 2/32" more tire thread than lower specs.
The leftovers or less than ideal tires are B and C spec which are then sent to wholesalers like Costco or other big box stores. This is apparently why they are $10-40 cheaper per tire when I compared them.
Is this true? Maybe I’m not using the appropriate terminology but I can’t find anything about this on google in general.
I’m getting new Michelin X Ice Snows from them next week. Supposedly 11.5/32" thread from mfg. Will confirm this but don’t have Costco Tires to compare to. Maybe on my next Costco trip, I can measure a display tire.
They only have one design of moulds for a given tyre, engineering a new set for “B” grade tyres would not be worth their while.