Catastrophic Lug Nut Stud Failure

[tonetonitony]

Trying to find out why this happened.

Little background info...
Boat (AZ220) and rig (eagle) are 5 years old
Replaced all hubs last year, new seals, races, bearings, and greased
Lug nut tightness was checked before departure

About 2 hours into a 3 hour haul the forward passenger side tire on the trailer decided to pop off. There was no warning what-so-ever. No shimmy, no wobble...just ejected out the side like a spent cartridge. (i've been in a car that had the studs fail one at a time)

Luckily i had room to work on the side of the road, and had an extra hub /tire / wheel to make it all work.

Upon inspection of the old hub i noticed that all the studs had broke off inside the hub...in exactly the same place ~ about 1/2 inch.

Everywhere i go no one seems to know why this happened. I did purchase these hubs @ a local trailer store. They were new stock but previously installed on other trailers and removed.

Could the studs have been inferior?
When looking at the trailer and how it rides on the road it does appear more weight is on the front axle. Could have been the load was too great and broke the studs?

Thanks for yalls help, trying 2 make sense out of this. It wasnt fun to deal with.

 

[EddiePetty]

Re: Catastrophic Lug Nut Stud Failure

"They were new stock but previously installed on other trailers and removed"

More than likely the studs had been over-tightened at some point in time and a fatigue line developed, probably about where the threaded portion ends.

I would suspect that as the hub and/or brake drum heated during your travels the resultand heat expansion pushed the studs beyond their yield point. After the failure of the first stud, a 'zipper effect' followed for the remainder, probably within a revolution or two of the wheel assembly.

 

[barbosam]

Re: Catastrophic Lug Nut Stud Failure

agreed, sounds like some one may have hammered those on good with an impact gun when they were previously installed.

 

[04fxdwgi]

Re: Catastrophic Lug Nut Stud Failure

Ahhhh. Did you torque the lug nuts or a tire shop do it? Sounds like probably the over-zealous use of an impact gun in action again. Some gun users think that the lug nut isn't tight till the gun stops turning the nut. Not true, as some of those guns can exert 225 lb ft of torque.

Also, be sure to torque them in the proper sequence, every other nut, clockwise or counter clockwise, in 3 equal steps till they are all the same.

My Eagle trailer manual states 110-120 lb ft of torque on the lug nuts.

 

[robert graham]

Re: Catastrophic Lug Nut Stud Failure

Maybe the guy with the wrench putting the same torque on your trailer nuts as he did on automobile or truck nuts. Trailer hubs and nuts not as stout as say a big pickup truck. A well-greased wheel stud is much more prone to over-tightening than one without grease. Of course for my boat trailer studs I always apply waterproof grease to protect from corrosion, but then I tighten my own lug nuts very carefully! Maybe you should check/replace those other wheel studs since they were all most likely tightened by the same gorilla! Good nobody got hurt!

 

[Silvertip]

Re: Catastrophic Lug Nut Stud Failure

Unless you have a trailer with a torsion axle, you cannot put more weight on the front axle than the rear because of the equalizer. Torsion axles are a different setup and can easily be overloaded -- such as by entering or leaving a parking lot.

 

[River-Runt]

Re: Catastrophic Lug Nut Stud Failure

Trying to find out why this happened.

Little background info...
Boat (AZ220) and rig (eagle) are 5 years old
Replaced all hubs last

I did purchase these hubs @ a local trailer store. They were new stock but previously installed on other trailers and removed.

Could the studs have been inferior?

I would also suspect the wheel studs. The studs should be grade 8 fasteners, which are high strength, heat-treated, alloy bolts. Unfortunately these high grade fasteners are prone to a condition called hydrogen enbrittlement. This occurs when the fastener is acid washed or plated during manufacturing and not properly "relief-baked" afterward to get rid of any hydrogen in the material. This condition would cause a sudden brittle failure like the one you experienced.

A materials analysis of the failed studs would determin if this condition was present, but that is probably further than you want to go in this failure analysis. It does however bring into question the condition of the wheel studs on the remaining hubs. If it was my call I would replace all the wheel studs.

 

[ac0j]

Re: Catastrophic Lug Nut Stud Failure

I have seen it happen because of loose lug nuts as well. The little amount of play will wear away at the studs rather quickly. BUT in this case I would say there were overtightened and stretched at some point.

 

[saumon]

Re: Catastrophic Lug Nut Stud Failure

If you don't mind, why did you change the hubs on a 5 years old trailer?

 

[bruceb58]

Re: Catastrophic Lug Nut Stud Failure

If you greased the lug nuts, you likely overtightened them. The torque specs for lug nuts are for them to be installed dry.

 

[tonetonitony]

Re: Catastrophic Lug Nut Stud Failure

If you don't mind, why did you change the hubs on a 5 years old trailer?

The trailer came with buddy bearings on it, I wasnt a big fan of them anyway because i couldn't apply grease to the spindle grease fitting. Last year we had a hub smoke so I decided to replace them all.

I would probably agree with most post about the studs being overtightened at some point in there life. That makes alot of sense. I personnaly tighten them to around 95#. I would love to find new studs 2 beat into those hubs. I was told they have "locking splines" and usually cost about $8 a pop. I've been all over and cant find what I need. Eventually i will replace the suspicious hubs.

Just reaffirms the ole addage..."u get what u pay for". I should have never dropped the coin 4 discounted previously used "new" hubs pre-greased.

 

[River-Runt]

Re: Catastrophic Lug Nut Stud Failure

While I didn't see any wheel studs listed on iboats a Google search for trailer parts turned up several suppliers. You could also bring the hub into a NAPA store and they should be able to set you up, they may be able to press them in for you also. As far as cost, studs are only a couple of bucks each.

 

[oldjeep]

Re: Catastrophic Lug Nut Stud Failure

I would love to find new studs 2 beat into those hubs. I was told they have "locking splines" and usually cost about $8 a pop. I've been all over and cant find what I need. Eventually i will replace the suspicious hubs.

Any auto parts store will have Dorman wheel studs available, just bring in one of your old ones so they can measure it. Shouldn't cost more than a buck or 2 each.

 

[Splat]

Re: Catastrophic Lug Nut Stud Failure

I would also suspect the wheel studs. The studs should be grade 8 fasteners, which are high strength, heat-treated, alloy bolts. Unfortunately these high grade fasteners are prone to a condition called hydrogen enbrittlement. This occurs when the fastener is acid washed or plated during manufacturing and not properly "relief-baked" afterward to get rid of any hydrogen in the material. This condition would cause a sudden brittle failure like the one you experienced.

A materials analysis of the failed studs would determin if this condition was present, but that is probably further than you want to go in this failure analysis. It does however bring into question the condition of the wheel studs on the remaining hubs. If it was my call I would replace all the wheel studs.

Well someone wanted to use big words today... tho you are correct in the condition, on a set of wheel studs it wouldn't have been the first place I would have gone. Atleast not without looking at the cracked component first. Now if these were titanium studs.... lol

I've been in the fastener business many years, when someone brings me a brokedown wheel stud I always suspect a overzellous kid with an impact gun first.99:1 its the root cause of failure, occasionally I will find crystalization, voids, or other tell-tale signs of HA, tho its rare, it does happen.

Bill

 

[sw33ttooth]

Re: Catastrophic Lug Nut Stud Failure

i might guess you hit a pot hole to fast and the harder a bolt is the more britle it really is. for instantance take the carbid steel from a snow mobile ski the steel is quite hard and temperd if you procede to brang it on concrete it will shatter like glass, however if you slide it across concrete it holds up great. you add that plus over tightened and 2 hours of stress theres your answer. i've put truck tires on before with an impact at 160 psi from the tank and have had them loosen i've also overtightened them to take me a half hour to get them off a few months later.

as for your bearing buddies phobia, you should still take them off every 1-2 years and manually inspect and regrease, bearins go bad and so do seals a $5-10 kit per axle isnt going to bankrupt any one. the nice thing is they get you through the season with out taking the tire off, you can just put a grease gun on it and wait till the water stops coming out.

 

[dockwrecker]

Re: Catastrophic Lug Nut Stud Failure

Here's something else to look at. Make sure your wheel has flush/flat contact with the hub. The wheel should clear the hub center easily and the hub face be free of any rivets. The back of the wheel needs to be perfectly flat with the hub. If it isn't it will pop lug nuts off in a big hurry. Drum brakes are the usual worst offenders for this when the wheel doesn't have enough back cut beyond the bolt pattern to clear some drum reinforcements. As a former wheel distributor, I've run into this several times especially on trailers.

 

[River-Runt]

Re: Catastrophic Lug Nut Stud Failure

Well someone wanted to use big words today...

Ha Ha, I couldn't help myself. Nothing brings out the mechanical engineer in me like a broken fastener!