Tow coupling and tensile bolt breaking !!.

[Robo]

Talking with outlaw other day, he's a grey nomad, ok.
The story goes he has a mate who had some trouble.

Tow bar couplings adjustable height apparently shouldn't be using Hi tensile bolts !!.

the push pull motion a trailer places on these can simply snap/shear a tensile bolt if used here.
where as a normal bolt will have some give to bend instead.
best I can explain it, seeing I heard it 3rd hand.

anyone have any experience with this ?
after some input please

[megatexture]

mm first ive herd but would like to know as i use one to level my camper as its got more clearance then the patrol .

if you use a normal grade bolt then it will flex? flex it to many times also and it will break also .

[NissanGQ4.2]

if you use a normal grade bolt then it will flex? flex it to many times also and it will break also .

Yes, but one would hope that when you you see the bent bolt you would replace it before it breaks

[BigRAWesty]

Depends on the tensile..
I would be using 8.8's as they are a good all round bolt. Sure 10.2 and above would be over kill..

Not 100% sure how they work but where is the slop?

[Robo]

My thoughts.
Tensile should be done up very tight.
that way the load is placed on the clamp area on both sides.
but after hearing this story, I'd like to know as I'm sure others would.
It may just be a matter the grey nomads have trouble doing bolts up tight enough.
we all weaken with age and injury.
but thought it was worth the thread none the less.

[BigRAWesty]

My thoughts.
Tensile should be done up very tight.
that way the load is placed on the clamp area on both sides.
but after hearing this story, I'd like to know as I'm sure other would.
It may just be a matter the grey nomads have trouble doing bolts up tight enough.
we all weaken with age and injury.
but thought it was worth the thread none the less.

If the setup is clamp like then the bolt should only take stretch loading as the friction between the 2 surfaces will stop them from moving.

Now a quick note, the spanner used to do up a nut is the length it is so the average man can reach its torque rating. 4.8 bokts that is.
But simply slip the ring of a second spanner over the end of the open end to extend the spanner length and tighten. Or a long 1/2" bar and socket.

[nissannewby]

My thoughts.
Tensile should be done up very tight.
that way the load is placed on the clamp area on both sides.
but after hearing this story, I'd like to know as I'm sure other would.
It may just be a matter the grey nomads have trouble doing bolts up tight enough.
we all weaken with age and injury.
but thought it was worth the thread none the less.

Bolts have a sheer and yield strength which is apart of their ratings. The higher the rating eg 12.9 the stronger they are in yield etc etc but yes they can become brittle. As its been said grade 8 bolts are most common and very good for this application. A little more may need to know about the application as it is very easy to break bolts if 2 opposing forces are put on them. A grade 8 bolt is more likely to bend before breaking but say a grade 12 will be stronger but won't bend as much before letting go.

[BillsGU]

Use the bolt that comes with the coupling. I have never heard of one of them breaking. If they do ..... go to court and sue for any damages ..........

[megatexture]

Yes, but one would hope that when you you see the bent bolt you would replace it before it breaks

Wheel stud bolts come to mind some get spotted early enough some don't unfortunately

[Robo]

Any comments?.
Did you buy a coupling new ?.
So what bolts are being used on it ?.
Or was coupling on the car when you got it ?, & not certain if bolts came oem.

Did the supplier tell or give you instructions for torque setting these bolts if needing to adjust height ?.

[NissanGQ4.2]

I had a bit of a look yesterday and it doesn't seem to be any ADR's in relation to what must be used