×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Lug nuts on wheels
2

Lug nuts on wheels

Lug nuts on wheels

(OP)
Does anyone know what the mechanisms are used to keep the lug nuts from backing out from the wheel?

This was after a discussion. I thought that it might be the centripetal motion of the wheel that causes a torgue on the nuts that drive it into the car. Someone else said that lug nuts are usually rounded or tapered and so are the the wheels, this causes increased surface area and thus increased frictional force that help the nuts from backing out.

RE: Lug nuts on wheels

2
When you say "backing out", I assume you mean loosen and rotate in the off direction.  

The mechanism that prevents this on a wheel joint is the same as it is for any threaded fastener joint: frictional forces between the contact surfaces of the fasteners and the clamped members.  The frictional forces are the result of preload.

Modern automobile wheel joints use either conical or spherical contact surfaces between the lug nut and wheel.  The use of these nonplanar contact surfaces removes play between the wheel and hub, and allows shear force transfer between the wheel and hub in the absence of preload, which is for enhanced safety.  

This joint is one of the few safety-critical joints that an end user actually loosens and retightens, and with the large variations present in threaded fastener joints, it is important to provide a larger operating envelope.

Regards,

Cory

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Lug nuts on wheels

I dont know, though I have assumed that maybe the flex of the rim (it pulls in a bit as you tension the bolt / torque the nut) and provides some constant preload to facilitate retaining tension within the connection, similar to the action of a spring washer.
Regards,
Lyle

RE: Lug nuts on wheels

Steel wheels often do have a built-in 2D belleville washer curve with relief at the bolt/nut, and contact at a 2 diameters, larger and smaller than the bolt circle.  It looks to me like that would do 2 good things.  First provide some stretch during torquing, and second to prevent a rocking action at the bolt/stud when the relatively thin steel wheel flexes during operation.

truck wheels have a maintenance re-torquing schedule. Gotta think if the studs were 6 diameters long they would have enough spring action to maintain torque even on the solid wheels

RE: Lug nuts on wheels

I think the mechanism behind torque bolts / nuts / etc. is fairly well established.  This is used in many parts of the car - head bolts and connecting rod bolts immediately coming to mind.

If I rememeber my college classes right, stretching the bolt generates a HUGE!!! clamping force and most of the force that is resistant to "backing off" is in the threads - friction - which is why you will see much discussion about the use of oil and antiseize compounds on torgued bolt threads.

RE: Lug nuts on wheels

Read a post on this site in another section, which described the use of lock nuts in general as a farce, which questions the suggestion I provided earlier.
Apologies and regards,
Lyle

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources