Johnmor
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| posted on 22/1/06 at 07:54 PM |
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sierra hubs
I'm about to fit my hubs to my viento hub carriers. One hub nut is a left hand thread, one is right. Am I correct in thinking that they should
tighten in the direction in which the wheel will turn or does it really matter?
Cheers
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RichieC
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| posted on 22/1/06 at 08:19 PM |
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The LH (nearside) wheel is LH and vice versa, yes it matters as they are designed to tighten and not slacken with forward motion.
Rgds
Richie
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JoelP
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| posted on 22/1/06 at 08:50 PM |
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ive never understood why a left or right hand thread makes a difference, once its all spinning at full speed theres only wind resistance trying to
undo it, and the acceleration forces will probably be less than braking forces. In fact wind resistance would undo a left hand thread on a left hub,
so that leaves me doubly confused  On a left wheel with a left hand thread, the wind slowing it would remove it, as would resistance to
acceleration, while braking would tighten it.
Or am i barking up the wrong tree?
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RazMan
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| posted on 22/1/06 at 10:42 PM |
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Barking 
The rotation of the wheel will be trying to take the inner bearing race in the same direction - ie. LH wheels will be rotating counter clockwise and
trying to turn the bearing in the same direction. Therefore a LH threaded nut is essential.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Liam
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| posted on 22/1/06 at 11:17 PM |
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Not quite
The bearing doesn't come into it. The hub is splined to the shaft and the nut simply holds the arrangement together, sandwiching the bearings,
purely by tension. Friction from the bearings (or the wind) can't apply any toque to the hub nut, and neither can simply the rotation of the
wheel in either direction. It's the inertia of the nut itself that is the issue.
Rotate a big heavy nut like that to a high speed (car doing 100 say) and it has a heck of a lot of energy. Suddenly slow the wheel down by braking
(or even worse instantly, by locking the wheel - by far the most torque you can effectively apply to that nut without a wrench) and you have a high
energy nut that just wants to carry on spinning. Too much of that, and if the direction is to loosen the nut, it wont stay on for very long.
That's why the sierra is set up so that on both sides, if a wheel is suddenly locked, the inertia of the nut is such that it wants to tighten.
The unconventional thread is therefore on the near/passenger side.
Personally it's a bit pointless if you ask me. Most vehicles just rely on stacking the nut to lock it, which works fine. In fact even a sierra
4x4 does this on the front axle - both nuts are conventional threads even though the hub/shaft/bearing arrangement is identical to the rear. Odd.
Liam
[Edited on 22/1/06 by Liam]
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