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


U-Bolts... To re-use or not to re-use?

U-Bolts... To re-use or not to re-use?

U-Bolts... To re-use or not to re-use?

U-bolts for auto and commercial vehicles, that hold and align the leaf springs. The general consensus is not to re-use u-bolts. There are a few common reasons, but I fail to see how any are valid.

One of the most common is the torque to yield idea that the u-bolt stretches but deforms and cannot be re-stretched, and is therefore garbage when undone. My thought is that wheel studs get really abused and re-stretched all the time, and no one bats an eye when they re-install tires on the old studs etc.

The other is the thread deformation concern that says the deep nuts used on a u-bolt deform the threads when torqued to spec. Upon undoing the nut, the u-bolt is again garbage. I find that theory a little hazy, as wheel studs again have deep threads. A commercial dually tire system called Budd wheel studs, have an inner nut that is also the stud for the outer wheel. These inner nuts have very deep thread engagement. Torqued to a good 550 lbs.

So for a 1.25" U-Bolt, I find it difficult to not re-use it, provided the threads are clean and not corroded away.


RE: U-Bolts... To re-use or not to re-use?

NOT an expert, but...what does the vehicle's service manual state is proper procedure? THAT's the authority in this question.

Wheel studs are probably a different material than u-bolts. Specially heat-treated for higher loads and multiple loadings on a safety-critical application. It could really ruin your day if your wheel studs broke. Case in point is an Isuzu Trooper II that I owned years ago. A very problematic vehicle. Starting with 3rd tire rotation, we began snapping off all the studs. The dealer blamed the tire store's heavy handed monkeys and their impact wrenches. After my engineering investigation, it turned out that the Isuzu stud supplier screwed up and produced a bad lot of heat treated parts. The Isuzu Regional Guy started replacing everything for free because he smelled "class action lawsuit".

If the u-bolts are "cheap enough", then why take the chance? What would happen if they DID fail?

Blue Technik LLC
Virtuoso Robotics Engineering

RE: U-Bolts... To re-use or not to re-use?

The recommendation to replace u-bolts is based on conservative engineering principles. The bent shape of the bolts, the flexible joint, means there is more possibility for damage and preload variation.

Regarding steel and heat treating, in general u-bolts and wheel studs are similar.

RE: U-Bolts... To re-use or not to re-use?

Agree with both above. Main difference is that forces on the U-bolts are different and could be more complex and more likely to be unforeseen (torque, bending, stretching, corrosion (winter, salt) etc) and above constructional limits.

Seen apart from rules and safety regulations is the great question: what could be the consequences if a re-used unit failed? Perhaps less than for an airplane or U-boat, but anyway .......

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! Already a Member? Login


eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close