Re: [FWDLK] Left hand lug nuts

[David Homstad <dhomstad@xxxxxxxxxxx>]

And here?s the rest of the story:

There are 2 physical reasons for using LH threads on the left side of the
car.
1.      There is a force called the ?Coriolis force? that applies to rotating
bodies. When a body is rotating the coriolis force points along the axis of
rotation. On opposite sides of the car, it points in opposite directions.
This was actually explained mathematically in my college physics class,
using Chrysler lug nuts as a practical application. My professor probably
had trouble changing the tire on his Chrysler at one time. This is a very
small force, but for large bodies such as the Earth and the Earth?s
atmosphere, this effect is large. This is why hurricanes always rotate the
same direction.
2.      When the wheel of the car is turning, the outer (closer to the wheel?s
edge) half of a lug nut has slightly more angular momentum (because it is
farther out from the axis of rotation) than the inner half. When the brakes
are applied, the two areas of the lug nut both want to continue this
momentum. Since the outer half has more momentum than the inner half, it
generates a small rotational force in the lug nut. On the RH wheels, this is
a RH (CW) rotational force, causing tightening with a RH thread. On the LH
wheels, this is a LH (CCW) rotational force, causing tightening with a LH
thread.

Chrysler engineers, being more engineering oriented than other
manufacturers, knew this and applied this to their cars as a safety measure.
But since both of these forces are very very small compared to the friction
of the nut against the wheel surface and stud threads, they have no
effective improvement in holding power. This is one reason why the practice
was discontinued. Another was probably complaints from owners and mechanics.
My guess the main reason was a cost savings.

Dave Homstad
56 Dodge D500

-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of Wayne Graefen
Sent: Monday, March 31, 2003 10:02 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: [FWDLK] Left hand lug nuts

http://www.thecarconnection.com/index.asp?article=5895

has a nicely written article regarding Chrysler's left hand threaded lug
nuts and explaining why the practice was dropped and where it came back too!

Good reading.

Wayne

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