Sevice wheelnut tightening

When our c/van is serviced  ,on collecting it they always Insist on hitching the van to the car checking all the lights work correctly and ensure  we watch while they "torque "  the wheel nuts,then they replace our telltales which then means a quick glance at them before each journey is all that is required

I agree that it would not have been either  of the major clubs .that would insist on the torque  settings at service

Different makes require different torque settings and vary more than you might think e.g. Lunar is currently 95nm and Swift 130nm for alloys. Settings can be found in your caravans manual and on my van at least on the weightplate. Spare steel wheels require different bolts (supplied) and torque setting are again different.

Stripped nuts can be very painful.

Try Veet instead of wax. 

I think that whoever said that they had been instructed/advise by the club is talking rubbish. You need to check for yourself what they should be. On an earlier Swift they were (I think) 130 Nm. Previous lunar (I think) 110 Nm. Current Lunar 95 Nm. 

I check torque before leaving home for each tour.

Whilst I agree that is the correct way to obtain a correct torque there is no way to actually check a torque (unless it is obviously moves when the torque wrench is applied). With recommendations to cheque torque every 20 to 30 miles after initial tightening it could extend time for a 100 mile motorway journey considerably to loosen off and retorque at such an interval. 

Not counting getting one's equipment out of wherever it is stowed, I reckon it would take just over a minute to loosen and retorque both wheels on a single axle caravan. Maybe this could be the basis of a new arena event for The National Rally . . . . ?

I referred to on motorways and the time would be taken on entering a service area, parking and exiting.

It's not as if one has to do it every 30 miles thereafter. The situation the advice is relating to is not that the nuts/bolts slacken but that the wheel has settled closer to the hub during running creating a gap between it and the nut/bolt head. 

I can't see why that would not apply every time that the wheels were retorqued? 

While experts advocate that caravan wheel bolts/nuts should be torqued/re-torqued every time the caravan goes out do they also suggest we do the same to our cars' wheel bolts ..... vehicles that do thousands of miles between services etc. Other than when removing a wheel on my car's for maintenace I never go anywhere near them with a wheel brace (I have a calibrated right arm)

I think you will find he set the wrench to 130Nm which equates to 96lb. which is correct.

Tell tales only show if a nut has rotated, but not if the bolt has stretched, and that would also negatively influence the clamping torque.

Yes, I do mean that the stud was overtorqued, but the nut need not unwind for the necessary clamping force to be reduced.

The tell tales as stated only tell you the bolt has turned.

Unfortunately here,  it is  however the tension in the bolt shank that clamps the wheel in place and loads the friction surfaces that stop the wheel moving against the hub.

The tell tales have not the slightest clue if the tension remains adequate to stop the wheel from starting to move and fret, as the bolt only starts to turn long after the required tension has been lost.

Wheel bolt tension is most typically lost because some thing or things have started to settle under the alternating forces. Of these dirt, plating, paint, surface corrosion or traces of grease are what typically "settles".

Unfortunately, by design our common caravan bolts have a short elastic length, the bit of the bolt elastically strained, so any settlement quickly reduces that all important bolt tension on which the wheel retention relies. Better designs feature a longer strained length to the bolt to reduce the magnitude of tension loss from similar settlements.

Or, as in challenging applications a bolt collar is introduced simply to increase the length of the bolt subjected to the strain. In our case this is offered as WSL safety bolts, the collar increasing this vital stained length by 3.5 times the normal.

There are arguments for tell tales on large number of bolt applications, greater than our 5, but basically these are to highlight where sloppy workshop or roadside practices can have left the odd bolt way under tensioned. With just 5 bolts on our heavily loaded wheels every one has to "pull its weight" or wheel loss is imminent, typically way before a tell tale would give any hint. They of course are in our caravans case a nice little earner for the retailers and makers.

All these threads about under or over torqued wheel bolts suggest that wheel fall off caravans every day ..... I've yet to see one. The closest I've come was following a trailer to the local tip when one of its wheels came off complete with hub! More a case of over loading than over tightening of wheel bolts.