the rubber meets the road

• the rubber hits the road

A metaphor derived from the point of contact between automobile tires and pavement.

• Audio (General Australian):

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the rubber meets the road

1. (idiomatic, with "where" etc.) A place or circumstance at which the implementation of a plan or intent is to be achieved.

   Synonym: (South Africa) the tackies hit the tar

   • 1957, Max Shulman, Rally 'Round the Flag, Boys!:

     Now we're getting down to where the rubber meets the road.

   • 2002, F. Stevens Redburn with Terry F. Buss, Public policies for distressed communities revisited, page 159:

     It can only be judged "when the rubber meets the road"; when its implementation does or does not produce results.

   • 2007, Dan Miller, 48 Days to the Work You Love, page 85:

     It is in the interview that the rubber meets the road.

2. Used other than figuratively or idiomatically: see rubber,‎ meet,‎ road.
   • 1928, How to avoid automobile accidents, page 30:

     Even 500 feet probably wouldn't allow you to brake to a stop, because it's "where the rubber meets the road" that counts.

• Almost always used with the prepositions that, when, or where.