Installing wheels, lugh nut torque?

[spacemarine83]

I just read the sticky that said for wheels the proper torque value is 148 lbs. That is really, really high!

That correct with aftermarket wheels too?

Putting on the drifts today with the tires. So I just really want to make sure that the 148 ft lb number is correct.

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[BmacIL]

Yes. The torque is based on the size and pitch of the studs not the wheels.

 

[scott_0]

I do 120, no issues for me since last year.........

 

[EFI]

I do 120, no issues for me since last year.........

Those crazy Ford engineers must have just taken a dart and thrown it at a wall full of numbers to determine the lug nut torque when designing the car.

 

[scott_0]

Those crazy Ford engineers must have just taken a dart and thrown it at a wall full of numbers to determine the lug nut torque when designing the car.

your witty sarcasm has prompted me to run out and retorque my lug nuts :hail:

 

[Freedom]

your witty sarcasm has prompted me to run out and retorque my lug nuts :hail:

well fuck.

 

[MtnBiker]

The M14 studs have a coarser thread pitch than the typical 1/2" stud (not as much mechanical advantage). Studs need to stretch a bit to provide adequate clamping (torque is an indirect measure of stretch). Between the lower mechanical advantage and the greater force required to stretch the larger diameter stud the torque setting is high.

 

[Kenbike]

Use the factory 148 ft lbs, so your rear aftermarket tire and wheel does not pass you on the highway doing 85!
I found out the hard way!

 

[cechk01]

Use the factory 148 ft lbs, so your rear aftermarket tire and wheel does not pass you on the highway doing 85!��
I found out the hard way!

Any pictures of the aftermath?

 

[chris_keller]

The M14 studs have a coarser thread pitch than the typical 1/2" stud (not as much mechanical advantage). Studs need to stretch a bit to provide adequate clamping (torque is an indirect measure of stretch). Between the lower mechanical advantage and the greater force required to stretch the larger diameter stud the torque setting is high.

Whether the threads or coarse or fine does not determine the amount of clamping force provided by torque of a given bolt, that's what the torque is actually doing. Coarse or fine threads determines the tensile stress area within a bolt, meaning, fine threads will have less stress in the bolt/nut at an equivalent torque spec due to increase in tensile stress area.

The clamping force based on a given torque value is F = T/(KD); where k is dependent on the lubrication present and D is the nominal OD of the bolt. Since no lube is applied here, K is assumed to be .20. So you torque a bolt down, look at nominal OD and whether lube is present and come out with a clamp force. That's how Ford came up with a torque spec, was based on the desired clamping force and stud sizes used on the car.

 

[MtnBiker]

The clamping force based on a given torque value is F = T/(KD); where k is dependent on the lubrication present and D is the nominal OD of the bolt. Since no lube is applied here, K is assumed to be .20.

From what I understand clamping force is kind of a black art unless you are directly measuring stretch with a strain guage. The k factor (nut factor in ISO), does take thread geometry into consideration along with friction. For practical purposes friction seems to be the larger variable. So I see your point.

 

[chris_keller]

From what I understand clamping force is kind of a black art unless you are directly measuring stretch with a strain guage. The k factor (nut factor in ISO), does take thread geometry into consideration along with friction. For practical purposes friction seems to be the larger variable. So I see your point.

Kind of. It's not really black science, just solid mechanics. The reason thread pitch is not taken into consideration in the K factor because K has more to do with energy loss (strain) in the materials as you tighten and friction between the components.

Thread pitch is accounted for as you torque something down anyway. Thread pitch is simply the axial distance traveled per degree of revolution of a bolt. Meaning, how far it travels down the bolt as you rotate the nut. When you torque something down, coarse threads require less degree of revolutions to achieve equivalent torque because axial distance traveled down the bolt is greater. Does that make sense? Ex, if you got two nuts hand tight side by side, then rotated a coarse thread nut and a fine thread nut 30 degrees, clamping force, required torque and stress in the coarse thread would be higher due to thread pitch.

 

[FranzVonHoffer]

Not an issue for me since I've got the PP so no spare, but 148 lb ft is why a lot of guys carry one of these in the trunk.

 

[kz]

From what I understand clamping force is kind of a black art unless you are directly measuring stretch with a strain guage. The k factor (nut factor in ISO), does take thread geometry into consideration along with friction. For practical purposes friction seems to be the larger variable. So I see your point.

In application where that matters, you actually do a series of torque tension tests for different bolt diameters, materials, threads, lube/no lube and so on. Calculations are typically way off and it is not extremely difficult or especially costly thing to do.

 

[Must_Tang]

Why are we arguing this point. It is 148.

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