Left hand Right hand thread, why?

[basement]

Why are some lug nuts CCW and others are CW?

[resq302]

Think it had to do something with the rotation of the wheel and the possibility of the lug nut spinning loose if it was not torqued down properly.

[JH27N0B]

The ones on the drivers side are more prone to loosen while driving if they tighten clockwise. That is why Chrysler made them tighten CCW.
Too many problems with people breaking the studs turning them the wrong way when trying to remove, so Chrysler eventually joined the club in the early 70's and made them all the same.

[drewcrane]

 

[NoMope Greg]

The ones on the drivers side are more prone to loosen while driving if they tighten clockwise. That is why Chrysler made them tighten CCW.
Too many problems with people breaking the studs turning them the wrong way when trying to remove, so Chrysler eventually joined the club in the early 70's and made them all the same.

That's exactly why they did it.  Most big trucks and buses are built the same way, due to the larger bolt circle.

[MEK-Dangerfield]

Thankfully they stopped this idea after 1970. You can convert over to all right turn bolts to save your sanity.

[Aussie Challenger]

  Modern wheels have a better taper on the lug nut and corresponding wheel surface. In the early days the surface area face was at a flatter angle and had less real force and the drivers side wheels would come loose. Also all wheels now centre on the axle protusion/hub leaving the nuts to only apply pressure to the back of the wheel against the axle flange.

[Chryco Psycho]

Freightliner & Western Star Trucks who are also owned by Chrysler also have left on the left side , it is to do with them being more prone to loosening on the left side with right hand threads as said above

[dodge freak 2]

People drove faster back in the 60's  Now a days its not needed 

[LAA66]

 Still got the original lefty driver sides. One of these days though.....

[Changin Gears]

8 3/4" rear end ring gear bolts are left also, so they won't loosen.