What does 'Where the rubber meets the road' mean?

Where the rubber meets the road is the most important point for something, the moment of truth. An athlete can train all day, but the race is where the rubber meets the road and they'll know how good they really are.

• Category: Transport & Travel
• This idiom is American English

Idioms similar to 'Where the rubber meets the road'

• Hit the road
• Rocky road
• Kick the can down the road
• There's never a road without a turning
• I'll cross that road when I come to it
• Fork in the road