5th Wheel Broken Stud Theory

[zimmysurprise]

Although we are currently running a Class C, several of my camping buddies are pulling 5th wheels. They keep having problems with broken wheel studs with the aluminum rims. They carry torque wrenches and are religious about checking them, but still occasionally break a stud on our trips. We generally write it off to cheap metal studs and heavy trailers, but I have another theory.

They all use those "super grip wheel chock" stabilizers between their tires when parked.They tighten down the threaded rod which pushes the tires away from each other. It holds the trailer still, but there is no torque wrench used on them. Trailer suspensions are designed to have some vertical give as the tires hit bumps on the road, but I don't see much lateral give except the bulge of the tires when you crank one of those chocks down. Is there a chance that continually using these are actually weakening the studs which eventually snap?

They say I'm smoking crack with that theory, but they can offer no explanation why. Please explain to me why this theory is wrong.

[ford_truck_guy]

Precision Instruments

[CharlesinGA]

deleted, duplicate post

[CharlesinGA]

If you are interested in carrying or owning a GOOD QUALITY CLICKER TYPE torque wrench for torquing wheels, that basically never needs calibration and won't get out of calibration and won't be damaged if you leave the tool set to a torque above zero, then I suggest the "split beam" torque wrenches made by Precision Instruments.

https://www.amazon.com/Precision-Instruments-PREC3FR250F-Silver-Torque/dp/B002XMSFIM

This has an 11° flex head to help with fender clearance and are a one way tool with a non reversing ratchet (so you also need to carry a breaker bar with you). Precision has been in business since 1938 and makes a very reliable tool. We had a number of these at work and the calibration room said they always checked perfectly (there is no adjusting them, they can only be scrapped if bad). I own both the 3/8 drive and ½ drive models. (I actually own about 20 different torque wrenches, with ranging from an 80 in/oz model, thats 5 inch lbs, to one that maxes out at 1100 lb/ft)

Here is the big one being used to torque the ball on my Blue Ox hitch to 450 lb/ft



Charles

[CabinetmakerII]

azdryheat wrote:
I've got 3 axles and have never lost a wheel stud. Perhaps people are using too much torque.

What Dry Heat said! We took our 43' Toy Hauler (retired 2020) to the East Coast and back, to Alaska and back, to Arizona and back for 8 years and never broke a stud. I checked lug nuts for tightness with my star wrench...

[Groover]

One of the characteristics of steel is that it will last forever if the stress applied is kept to less than 50% of yield strength. One you go over 50% it lasts a number of cycles of the stress being applied and removed with life going down as the stress goes up. A bolt stressed at 90% yield strength will last forever if the stress is not relieved and re-applied.

In a proper design a bolt that is properly tightened holds 2 objects together with such force that they will not be pulled apart, thus changing the stress on the bolt. The rigidity of the flat face of the wheel against the flat face of the spindle should far exceed that of the bolts. So, unless there there is a mechanical defect in the flat faces causing them to rock the bolt should not be stretched enough to change the stress on it IF IT IS PROPERLY TIGHTENED. BEING OVERTIGHTENED WILL NOT CAUSE THE BOLTS TO FATIGUE WHILE IN USE or result in a failure while in use. Failure from overtightening should only occur during the tightening process.
Most fatigue failure is caused by bolts not being tightened enough! This allows the wheel to pull away from the hub at times, creating a cyclical stretching/stress increase.

So the failure in use is due to LOW TORQUE, mating surfaces that are not flat or possibly the stretching/shrinking cycle resulting from brakes heating up and cooling off and the different coefficient of expansion of the two metals. Having said that, the aluminum wheels that I just bought have steel inserts in the bolt holes to help prevent this situation.

If my trailer was to have trouble with studs breaking I would make sure that the lug nuts are tightened enough, that the wheel to hub mating surfaces are flat and smooth, that there are steel inserts in the aluminum wheel lug holes and that the brakes are working evenly so that one or two are not getting much hotter than they should.

On edit, one more thing to consider, especially if the trailer did not come with the wheels on it. I changed my trailer from steel to aluminum wheels and had a terrible time finding lug bolts the right length. The lug bolts that came with the steel wheels were too short and all that I could find at the parts houses were too long, in both the unthreaded shank and overall length. I finally found some on Amazon with the right shank but were still too long. I was able to cut them to length. I actually just got that done a couple of weeks ago so it will be a while before I can swear that they are reliable.

[Ron3rd]

Never had a broken stud in 35 years. Somebody is incompetent
3 TRAILERS by the way

[Gjac]

Many years ago(1975 or so) my friend and I borrowed his fathers Class C and drove to Florida to stay with my parents in south Miami for two weeks. On the way back we noticed a vibration so we pulled over and everything looked OK. Started the MH again and noticed the same vibration above 5 mph. When we shook the outside rear dual tire it was loose and riding on the hub extension the only thing keeping it on the hub was the fender skirt. We had 3 young kids 2 years old to 5 months old at the time. We saw every stud was sheared completely off when we took off the wheel cover. We were very thankful it did not come off we did not crash with our young kids in the MH. This happened at 1 or 2 in the morning and no one stopped to help. Finally someone stopped to help us going south on I95 we were going north and he found a gas station that was open with no mechanic 20 miles away. The guy running the station had the studs and allowed us to pressed them in. The only thing that we figured is new tires were put on before we went to Florida but the rims back then were just flat if I remember correctly and over about 3000 miles of travel worked loose and the vibration work hardened the studs until they failed. Having said all that I think a TT sees more vibration than a MH or car and if the rims are flat like my boat trailer I can see were that can happen. Rough roads could be 10 times the static loads that those studs can see, all in shear.

[markchengr]

When I did maintenance on large marine engines for a living we were required to have all of our torque wrenches sent out and recalibrated once a year. They do get out of spec with regular use.

[dougrainer]

1. Is it possible the Torque Wrench is way out of calibration?
2. Is it possible they are NOT using the CORRECT Torque?

[fj12ryder]

But you also won't know if the nuts are torqued to spec. So if they actually know how to check the torque settings, they know the nut has to turn to check correctly. So it could very easily lead to over tightening and eventual breakage. Not that I've ever heard of many wheel stud breaking.

[Lynnmor]

fj12ryder wrote:
But if the torque wrench clicks and the nut doesn't move, that doesn't mean the nut is at proper torque. A bolt/nut needs to be moving to get the torque correct. If the wrench clicks when the nut is stationary, you're looking at static friction, not necessarily proper torque setting. The bolt/nut has to be moving when the wrench clicks.

That will give you the correct torque but the subject is broken studs. You aren't going to break studs by using a wrench and not moving anything.

[fj12ryder]

Bird Freak wrote:

Lynnmor wrote:

Bird Freak wrote:
I was a Snap-on tool dealer for about 4 years. If you keep checking them without backing them off first you stretch the bolt a little each time.

Quite the opposite, if the bolt is checked and it didn't move, it can't stretch. If it did move, then you are just doing a proper torque.

Problem is most folks don't know how to properly use a torque wrench and will move it a bit.

Well, that is the proper way to use a torque wrench. Using it on a stationary nut isn't correct. As you tighten the nut, when the wrench clicks, it's correct. Stopping and checking is not the way to do it.

[dougrainer]

I wonder if the failures the OP's friends had came from adjusting/checking Torque on HOT wheels, instead of waiting for them to cool to ambient temp? YES, CORRECT recheck of Torque requires you to loosen and THEN tighten and Torque. AND, following the correct Torque sequence. Which is almost 180 degree across each lug nut. Doug

[Bird_Freak]

Lynnmor wrote:

Bird Freak wrote:
I was a Snap-on tool dealer for about 4 years. If you keep checking them without backing them off first you stretch the bolt a little each time.

Quite the opposite, if the bolt is checked and it didn't move, it can't stretch. If it did move, then you are just doing a proper torque.

Problem is most folks don't know how to properly use a torque wrench and will move it a bit.