I have done it "by feel", with no problem. My W123's use the standard tapered wheel bearings like most cars. Indeed, the same PN as many cars (SET3 & SET5, I recall and know one is used in GM trucks), so why must adjustment be M-B finicky? Main thing is not to over-tighten them or they will swell from heat and seize in a few miles, sometimes welding the inner race to the spindle.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans