My 2012 caravan has always been workshop serviced so, as I am having new tyres fitted, this is the first time I have removed the wheels myself. On doing so, I found that the bolt threads have been greased. From my engineering days, this is contrary to the proper practice - these wheel bolts requiring no different treatment than for car wheel bolts.
I am using a degreasing agent to clean bolt and drum threads (Q-tops in the case of the drums), but decided to get authoritative confirmation.
First port of call, Al-ko Technical dept, the chassis manufacturers. Their own handbook, supplied with caravan, says the M12 bolts should be torqued to 110 Nm - no mention of dry or lubricated threads - but a phone call advised that members of the public contact their dealership, and call menu denied further pursuit in this direction.
Swift caravan legend plate says 130 Nm torque, whilst their handbook says 115 Nm torque. It says mating and sealing faces of wheel and nuts should be clean and dry, but no specific mention of the threads.
Strangely, the Caravan Club technical dept have no specific guidance regarding thread lubrication, or not, although they did confirm that Swift changed the torque load to 130 NM in 2012, so looks as if I got an out-of-date handbook with the van.
Looking at various engineering data sheets on line, for torque specs for my bolts - M12 10.9 rated - I find that dry threads (including those with "protective oil film" at manufacturing stage) have a torque spec of 127 to 140 NM, depending on which data sheet, and a torque of 110 Nm for lubricated threads (remember the 110 NM in Al-ko handbook?).
In the recent past, on caravan forums, there have been discussions about the alloy wheels of caravans becoming detached whilst towing, but without any definitive conclusions as to the cause.
From a legal point of view, a caravan under tow is subject to the same laws as motor vehicles concerning usage and maintenance, so in the event of a detached wheel causing an accident involving the police, the caravan owner could find him-/herself in a very awkward position.
IMHO, caravan manufacturers have been allowed to sit on the fence for far too long, and it is time they were "put on the spot".
Even caravan service workshops would seem to be left to their own devices on this - and bear in mind that applying a dry thread setting to a lubricated bolt can take the bolt into its 'point of yield' range, where the bolts could snap off at any time during towing.
So why have the service depts not pressed the caravan manufacturers into being forced to clarify the position?
I am using a degreasing agent to clean bolt and drum threads (Q-tops in the case of the drums), but decided to get authoritative confirmation.
First port of call, Al-ko Technical dept, the chassis manufacturers. Their own handbook, supplied with caravan, says the M12 bolts should be torqued to 110 Nm - no mention of dry or lubricated threads - but a phone call advised that members of the public contact their dealership, and call menu denied further pursuit in this direction.
Swift caravan legend plate says 130 Nm torque, whilst their handbook says 115 Nm torque. It says mating and sealing faces of wheel and nuts should be clean and dry, but no specific mention of the threads.
Strangely, the Caravan Club technical dept have no specific guidance regarding thread lubrication, or not, although they did confirm that Swift changed the torque load to 130 NM in 2012, so looks as if I got an out-of-date handbook with the van.
Looking at various engineering data sheets on line, for torque specs for my bolts - M12 10.9 rated - I find that dry threads (including those with "protective oil film" at manufacturing stage) have a torque spec of 127 to 140 NM, depending on which data sheet, and a torque of 110 Nm for lubricated threads (remember the 110 NM in Al-ko handbook?).
In the recent past, on caravan forums, there have been discussions about the alloy wheels of caravans becoming detached whilst towing, but without any definitive conclusions as to the cause.
From a legal point of view, a caravan under tow is subject to the same laws as motor vehicles concerning usage and maintenance, so in the event of a detached wheel causing an accident involving the police, the caravan owner could find him-/herself in a very awkward position.
IMHO, caravan manufacturers have been allowed to sit on the fence for far too long, and it is time they were "put on the spot".
Even caravan service workshops would seem to be left to their own devices on this - and bear in mind that applying a dry thread setting to a lubricated bolt can take the bolt into its 'point of yield' range, where the bolts could snap off at any time during towing.
So why have the service depts not pressed the caravan manufacturers into being forced to clarify the position?