Why are they called '5th-wheelers' ?

[JohnD]

Reading around the chats has got me to wondering why 5th-wheel trailers are called '5th-wheels'?

Wouldn't the 5th-wheel be the spare tire?

Maybe they should be called 'pick-up truck bed hoggers' instead . . . ?

Anyone know where or why the term '5th-wheel' came to be?

Just a random though bouncing around inside my pea brain early on a Saturday morning . . .

 

[danemayer]

Here's one explanation.

 

[wdk450]

John:
Here is the article on the subject from Wikipedia: https://en.wikipedia.org/wiki/Fifth-wheel_coupling

I remember seeing somewhere an early 5th wheel automobile hookup that used the spare tire laid horizontally with a bearing in place in the hub as a hitch point for a trailer hitch pin.

 

[dlw930]

Horse-drawn wagons and buggies having 4 wheels and a turning front axle had mating steel plates or members through which a pivot pin permitted the front axle and wheels to rotate/turn as the horse(s) turned. This assembly of pivoting steel plates was called the "fifth wheel". This assembly served the same basic purpose as the pin box/hitch combination on our modern 5th wheel RV's.

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