Towball bolt torque settings

[woodsieboy]

I am planning to replace the 12N and 12S sockets on our car with a single 13 pin socket. To do that I will have to remove the towball which is the fixed type. Can somebody tell me the torque settings when replacing the 2 bolts that hold the towball onto the towing bracket please?

Thank you

 

[Damian]

With a M16 Bolt with nyloc nut its 225Nm
with a non nyloc nut its 252Nm

 

[Mel]

Once fitted, is there any need to periodically check the torque on the tow ball bolts, like you do on the wheel nuts?
mel

 

[Damian]

HI Mel, Towball bolts do not need the same amount of checking as caravan wheels.
Maybe once a year is enough but they shouldnt have moved.

I shoud have added in my last posting that you should not reuse towball bolts, you should use new ones once the originals have been undone.

 

[JTQ]

The towball securing bolts have a much longer stressed length and so can store more energy in their elasticity and thus be very much less prone to slackening. They are also not subjected to the alternating shear and thermal changes that make life more difficult for the short and thus low stored energy bolts typically used on our wheels.
It is prudent to check them but unlikely they will have relaxed.

 

[Paul_5041263]

It is not the bolt that should not be used again it is the nylok nut which after use should be discarded for a new and (in theory) undeformed one.

 

[Damian]

All the towbar manufacturers recommend the replacement of nut and bolt.#
I think they may know best somehow.

 

[Brum1]

I would much prefer to use "Nyloc" nuts but can only seem to find standard bolts and nuts with silly little shakeproof washers, even the more robust split type washers seen to have disappeared.
or am I spending too much time in Towsure?

Brum

 

[Sproket]

I would much prefer to use "Nyloc" nuts but can only seem to find standard bolts and nuts with silly little shakeproof washers, even the more robust split type washers seen to have disappeared.
or am I spending too much time in Towsure?

Brum

Try your local nut & bolt / fastener supplier

have a look on Yell.com .......

 

[SirRogerFFS]

Being a retired engineer certainly would not use the same nut and bolt on the tow ball twice I think what Damian should have said in his thread was change both as its the thread on the bolt that will have stretched and certainly only use the nyloc once

 

[Damian]

You are right, I should have said change both in the first posting.

 

[kennygee]

Would it make any difference if an extra nut was put on the bolt to "lock" the nuts together

 

[Damian]

On most fixed towballs I doubt there is room to get another nut on, and get the spanner out after, but as long as the correct torque is applied to the fixing, it is very unlikely to move.

 

[woodsieboy]

Thanks to everybody for their input and suggestions,I have changed the electrics to single 13 pin socket,and have replaced the towball bolts with new ones,I just felt that for the cost of the new bolts it was not worth taking a risk.

 

[JTQ]

Would it make any difference if an extra nut was put on the bolt to "lock" the nuts together

Yes, it will screw up the torque-up tensioning and so is unwise in this case.
With the tension levels being generated in the long-ish bolt shaftused here there will be quite a level of strain, 'elasticity'. This will store a lot of energy that keeps the nut hard against the mounting and so largely obviates the need for any supplementary locking device.