Amphicar wheel nut (lug nut) tightness torque setting.


David Chapman

Following on from my last post...

I've never known exactly how tight the wheel nuts should be, but as we all know
they are the same as on the early 1960s Mercedes so I thought I'd ask the
question on the Mercedes 190SL newsgroup, after much debate I got this answer:

"David C. asked what the correct torque setting is. The correct setting is 110
Nm (81 ft lb.) Why, I can't answer the why. Some German engineer must have
considered the stud property class, nominal diameter, thread size, friction
coefficient and use.

What he didn't compute was the force needed to remove the lug nut after the car
had been driven for a year or three. The short handled 190SL lug wrench doesn't
provide sufficient mechanical advantage to remove the wheel if you have my
physical traits: 55 years old, 155 lbs and out-of-shape.

For everyday driving, I apply a drop of tranny fluid to the stud and apply 65 ft
lb. of force to the lug nut. For track driving I set it at spec 81 ft lb. "

David Chapman
(I've got a shiny new torque wrench and I'm not afraid to use it !!)


Typically lug nuts for the average auto and light truck should be set
to 65 Ft/Lbs. Any more than that and you stand a good chance of;

1 - Stretching the studs and making them prone to breaking.
2 - Making the wheel tough to remove.
3 - Deforming the wheel, increasing the chances loosing a wheel.