Wheel Nut safety?

[pfenlon]

I was always under the impression that a nut must screw onto a bolt by at least the diameter of the bolt, for safety reasons.

Is that correct, or something that I dreamed up along the walk of life.

Any experts out there please.

[michaelfinnis]

In industry(aviation) a nut needs at least one thread of the bolt showing through the nut when torqued up to be considered in safety.

[c.hydes]

25 minutes ago, michaelfinnis said:

In industry(aviation) a nut needs at least one thread of the bolt showing through the nut when torqued up to be considered in safety.

Is that so that you can see that bolt is fully screwed through the nut? I was led to believe that maximum strength of a threaded nut/bolt joint came from 5 full threads, anymore does not increase the strength !!

 

C/ 

[RobH]

The answer is not simple as it depends on the design and materials to some extent.  

https://mobiletechengineering.com/2020/12/03/thread-engagement-how-much-is-enough-12-2-20/

Standard nut depths are calculated on the basis that all the threads should be engaged, which means the tensile strength of the joint is always higher than that of the bolt or stud itself.   If there is a locking feature such as a nyloc collar, the thread must extend right through it in order for the locking to be effective.

Bear in mind that it is common for wheelnuts to have the first few threads undercut for ease of initial location, so the thread length doing the work is less than the full length of the nut. 

Edited October 3, 2023 by RobH

[Motorsport Mickey]

Speaking as an expert (well engineer anyway) I was always taught to allow for a 1 dia and a half of the bolt or threaded fastening as a rule of thumb (depends upon how long your thumb is) to allow for differing thread materials. see attached.

 

How does Thread Engagement Effect the Tensile Strength of a Bolt/Joint Combination?

Simply put, more thread engagement can result in higher tensile strength a joint.  Tensile strength is the force required to pull something until it breaks or the capacity of that material to withstand that load.  If a bolt is longer than needed to develop full tensile strength in a nut member, that excess material is wasted. On the flip side, if there is not enough bolt length engaged in a nut member, the bolt has a higher probability of stripping out before full tensile strength capability is achieved. Depending on the strength of the nut material, you need at least 1-1.5 bolt diameter engaged in the nut member to achieve optimum joint strength with a thread forming fastener.  One factor that affects this is the nut material. Steel is a close to a 1-1.5 relationship, while softer material, like plastic will need more thread length engagement to achieve optimum joint strength.

Mick Richards

[BlueTR3A-5EKT]

So not up till it goes soft then back a flat?

[Lebro]

[iain]

I’m intrigued…….the title of this thread is wheel nut safety. I’ll hazard a guess…..is the question because the wheels being fitted with wheels nuts means the stud are are short? (A problem seen when trying to use a wire wheel solid rear axle with steel rims.) 

[pfenlon]

11 hours ago, iain said:

I’m intrigued…….the title of this thread is wheel nut safety. I’ll hazard a guess…..is the question because the wheels being fitted with wheels nuts means the stud are are short? (A problem seen when trying to use a wire wheel solid rear axle with steel rims.) 

I do not like wheel spacers of any kind and find that my front wheels have been fitted with 2 per side. the front wheel nuts only screw on 4.5 times, which is not enough in my opinion, the rears more than double that.  I will look to change the wheels for standard units.

[iain]

Are the spacers permanently attached to the wheel?

[michaelfinnis]

16 hours ago, pfenlon said:

I do not like wheel spacers of any kind and find that my front wheels have been fitted with 2 per side. the front wheel nuts only screw on 4.5 times, which is not enough in my opinion, the rears more than double that.  I will look to change the wheels for standard units.

Spacers can be used quite correctly to fit wire wheels. Without them the studs have to be cut down or replaced with shorter ones, otherwise they foul the wheel. Can't see any other reason for using them. It doesn't matter how many turns a nut is screwed on,what is important is that all threads are engaged ie. the stud/bolt protrudes through the nut. I presume the nut has more than 4.5 threads though?

[TR4Tony VC]

I go with 1.5 x dia meter = threads, so on the 7/16th I’m looking for 12 threads at least.

I have still ripped a wheel off having said that (an ARE mag as it happens at about 80mph on the M40 one night on the way home) - that looked like the aftermath of losing one stud / nut of 4 which loaded the other three up, so it still happens. I had a well known suppliers very nice stainless wheels nuts on, so I doubt that they were the problem.

4.5 just is nowhere near enough I’m afraid, especially with modern sticky road tyres so I would sort that one out pdq.

Regards

Tony