Axle nut torque

[dghii]

I know the value to torque new Axle nuts is 340 Lb-ft, but...

I recently removed front wheel hubs and replaced wheel bearing. I knocked out a few worn items while in there, such as tie rods, lower control arms and drop links.

I bought new axle nuts and torqued to correct value got a wheel alignment and all is well.

Question: Why is the front axle nuts torque specification such a high value? All they hold on is the stub axle. I can see the high value on the rear where you are connecting the drive axles to the hub, but the front sure seems like overkill. My guess it its a 'left over spec from the 996 4S cars...same hub and nut I would guess.

What am I missing?

[Filastein]

Torque is, by and large, a value of the size of the fitting. Big thread diameter = big nut = big torque.

That and Porsche's desire to limit part count. I believe the front hub is the same part as the rear, just with different hardware behind it.

[Gilles]

Originally Posted by dghii

I know the value to torque new Axle nuts is 340 Lb-ft, but...

Question: Why is the front axle nuts torque specification such a high value? All they hold on is the stub axle. I can see the high value on the rear where you are connecting the drive axles to the hub, but the front sure seems like overkill.
.
What am I missing?

dghii,

I believe that the high torque is required to keep the dual row bearings together.

.

[dghii]

I hope not!

[steved0x]

The clamping force on the inner races is important, the friction of the 2 inner halves on the hub is nit enough, it is why you are not supposed to roll the car with the axles out.

[lkchris]

Originally Posted by Filastein

Torque is, by and large, a value of the size of the fitting. Big thread diameter = big nut = big torque.

Exactly.

And, when you tighten something to a torque value, you are stretching or distorting the component, creating permanent tension. Takes big power to do this to a big part.