wheel studs

G'day Big Bird
I presume you mean 5 studs on the one wheel and not 5 distributed among the 24.
If left slightly loose the wheel/axle spigot is the only item bearing the load and the studs get hammered sideways which breaks them off.
The studs should clamp with sufficient frictional grip to hold the wheel securely against the hub face.
Overtightening does also stretch and damage studs and despite most people knowing the dangers of overtightening when new tyres are fitted, they still allow fitters with impact guns to tighten the wheel nuts.

If the vehicle is fitted with alloy wheels and the hub has been heated by braking, then the sudden cooling, like going through a river crossing will chill the wheel and make the studs slightly loose. Then they become very loose and usually the wheel falls off if the situation goes unnoticed or the stud tightness isn't checked after the chilling.

Was the vehicle used on rough roads at near GVM? If so, that will place unusually high sustained loading on components. You will probably break after a period of working at your personal GVM loading.

I regard GVM and max towing weights in the same category. It is the limit of, and not the normal operating condition which the vehicle should be used under. It is always wise to have a safety margin or a level of insurance.
Don't always believe the manufacturers claimed figures, they are competing against other manufacturers for sales. Something has to be pushed to the limit. I wonder what that could be?

Big Bird
Had the same thing happen to my vehicle as well, sheared 1 x stud and 2 out of the remaining 4 were loosened.
I believe that the 1 that sheared off was overtightened and the other 2 not tight enough AFTER the vehicle had been at tyre repair shop.
As a reference I have alloy wheels fitted.
This happened halfway between Karratha and Newman on the Roebourne Wittenoom road, which is rough in places but not too bad when I was travelling.
I managed to arrive at Newman without major incident and replaced all studs on that diff in case the other side studs were stessed,and never had an issue since.
Have a strict practice now at tyre shops of refusing them to use a rattle gun on the tightening of wheel nuts on my vehicle, and tension them myself at home.
Some of those rattle guns can generate some pretty serious torque.
Cheers
Paul

We have one of those 12V "rattle" guns. I am always concerned about over tightening them. When putting the wheel nuts on, I go to one click and finish with the wheel brace.

Phil

I keep a spare set of studs and nuts, front and rear in the Patrol, it is common on GU's. Another problems are with aftermarket wheels where the centre hole in the wheel is not the same as the hub diameter, this is a common problem on trailers as well. The load is on the studs only!! Also as you mentioned, overtightening is a problem, best to loosen and tighten with a torque wrench after new tyres are fitted or if removed for wheel balance. Michael.

I have noticed that the tyre centers around me now use a Tension wrench as the final tightening tool? So something has happened.

I used to be a wheel stud. Wheely, ask my wife..:-)

Big Bird

I keep a tension wrench permanently in my car. It is the only way to be sure they are as close to factory specifications as possible. You may find your problem is not solely due to nut tension. Just about every car in the country would have had its wheel nuts over tightened many times but only a tiny minority break. Most of these seem to be 4wds. It could be a combination of over stretched studs combined with load, speed and road surface. Stiffer aftermarket springs and larger diameter tyres don't help either.

Ross M is right about GVM and towing capacities. The advertised limits are for good conditions only and then not all the time. I remember working at the October Bathurst race in 1963 to '66. The cars were stock standard in those days but many suffered major mechanical problems after only a few hours of high speed driving. Some of the specially built EH S4 Holdens broke tailshafts and tore the centres out of their wheels. All of those cars would have gone for years in normal street use without any problems.

Your typical city based 4wd owner will have two weeks of school holidays so they will load the car to the limit or beyond then roll out of Sydney or Melbourne to see the Kimberleys via the Tanami track. They then wonder why things break.

I don't know what your circumstances are. Your problem may have been nut tension and nothing else but there could also be a lot more to it.

You may find the informatin in this link useful.http://www.caravanandmotorhomebooks.com/articles/why_wheels_fall_off.html