What the heck are "king pins"?

I’ve been looking at a bunch of adds for old trucks. “new king pins” or “needs king pins” is an often seen comment. So what are they? A search on Yahoo! was fruitless.


Dictionaries save the day again.

These are the pins on which the front wheels pivot - when worn, the front wheels shimmey - replacing them is a fairly expensive operation.

p.s. - by the time the kingpins need replacing, the entire suspension and drive train are also suspect.

King pins are an alternative to ball joints in designing part of a vehicle’s front suspension. Technologically, they’re rather primitive nowadays. As far as I know, they’re currently used only on some trucks. Decades ago, they were also used on some passenger cars. As happyheathen’s post indicates, either needing kingpins or having new ones can significantly affect what one will spend on repairs.