I know this must really drive you crazy because your attention to your MB's is exemplary! I take pretty much every car I own to Discount Tires whenever I need tires. I am completely satisfied with how every one I've been in runs their business. Always professional and by the book from what I can tell. And they do use a torque wrench to do the final tightening of the lug nuts.
My only complaint is that they will just pop off hubcap or center caps and let them smack face down on the concrete. If I take one of the MB's in I always pop off the hubbies as soon as they pull it into the bay.

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John