Wouldn't ABS brakes have a lot to do with this? In ABS sytems the brakes never truly lockup and the intermittent braking action also helps maintain control, while reducing heat and fade. I wouldn't be surprised that they would shave 25% off of stopping distances. My 82 doesn't have them, but some cars had them as early as 84 I believe....not sure about the 85 300D?

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1976 240D
1987 560SL
2007 E320 Bluetec
1998 C280 (now son’s car)
1982 240D Manual - Sold