“Where the rubber meets the road” means when a vehicle’s tires go on the road and face a performance test. “After ail is said and done it must be remembered that ‘the rubber meets the road’ and the riding comfort and economy of transportation is to an appreciable degree because of the tire” was cited in 1927, referring to Firestone tires. Firestone advertised a “where the rubber meets the road” jinge in the 1960s and 1970s.
 
“Let’s get down to where the rubber meets the road” was cited in 1956 in a business context—not involving tires.
 
   
Wiktionary: the rubber meets the road
Etymology
A metaphor derived from the point of contact between automobile tires and pavement.
Phrase
the rubber meets the road
1. Used other than as an idiom: see rubber,‎ meet,‎ road.
2. (idiomatic, with “where” etc.) A place or circumstance at which the implementation of a plan or intent is to be achieved.
   
Wikipedia: Firestone Tire and Rubber Company
The Firestone Tire and Rubber Company is an American tire company founded by Harvey Samuel Firestone in 1900 to supply pneumatic tires for wagons, buggies, and other forms of wheeled transportation common in the era. Firestone soon saw the huge potential for marketing tires for automobiles. The company was a pioneer in the mass production of tires. Harvey Firestone had a friendship with Henry Ford. Firestone used this relationship to become the original equipment supplier of Ford Motor Company automobiles, and was also active in the replacement market.
(...)
Television advertisement jingle
Where the Rubber Meets the Road is an advertisement jingle that was frequently used in the 1960s and 1970s, especially on televised sporting events.
 
Wherever wheels are rolling,
No matter what the load,
The name that’s known is Firestone
Where the rubber meets the road
 
13 February 1927, Wichita Daily Times (Wichita Falls, TX), pg. 37 (?), col. 5 ad:
And it is indeed gratifying for the Firestone Tire to have played a part in Bulck’s euceess. After ail is said and done it must be remembered that “the rubber meets the road” and the riding comfort and economy of transportation is to an appreciable degree because of the tire.
(Dixon Motor Company—ed.)
 
29 May 1956, Humboldt Standard (Eureka, CA), “Hollywood Today!” by Erskine Johnson, pg. 4, col. 5:
The jargon gets a king-sized airing on the screen in the new movie, “The Great Man.”
(...)
How much is it going to cost?: “Let’s get down to where the rubber meets the road.”
 
31 July 1957, Sacramento (CA) Bee, “Gray Flannel Suitisms Haunt Conference Panels” by Hal Boyle (AP), pg. A-10, col. 2:
“Let’s get down to where the rubber meets the road.”
 
OCLC WorldCat record
Looking at the trouble spot where the rubber meets the road.
Author: W E Meyer
Publisher: 1964.
Edition/Format:   Book : English
Publication: SAE Journal, Vol. 72, No. 10, Oct. 1964, p. 36-40
 
Urban Dictionary
Where the rubber meets the road
where the action is most immediate, such as the place where a plan is put in motion (from the place where a vehicles tires make contact with the pavement)
If she can tell where the rubber meets the road, she’s in.
by The Return of Light Joker November 05, 2009
 
YouTube
Commercial - Firestone Tires - Where the rubber meets the road!
Video Archeology6
Published on Jun 28, 2014
Brought to you by http://www.videoarcheology.com