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Quote: Originally posted by Thwack on 18/1/2010

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Hi

As I understand it wheel bolts should be torqued up with clean dry threads.


Thwack

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Exactly right...

 

no mention of lubrication here but as retired motor engineer i can say it is not a good idea to add grease of any kind to a wheel bolt because it will lose tension and grip.see

www.al-ko.co.uk

Caravan Chassis HandBook

Quote: Originally posted by trez321 on 20/1/2010you can always use graphite

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I wouldn't even consider PTFE spray; it still has lubricating qualities that will change the correct strength of the torque compared to a dry bolt.

All wheel bolts have "dry thread" recommended for torquing, so any additive away from that state is contrary to recommendations.

Bertie.

I would say it was a very grey area.

Whilst Alko specify the tightening torque for clean dry bolts, they are referring to new bolts. Once they have been in service and the slightest bit of rust builds up, the nut becomes tighter in the thread and therefore the tightening torque is different.

A small ammount of lubrication will overcome the rust build up. An example of this is that if you take a new nut and bolt, the nut will spin up the bolt easily. If you take the same size nut and bolt that has been outside for a few months, it is a very different story. Imagine how much different it would be if it was repeatedly heated and left to cool and had been outside for a few years as is the case with a caravan. If you also took the same nut and bolt, covered it in grease and left it outside for a few months, you would find the thread resistance on the greased bolt to be far closer to that of the new one than that of the rusty one.

The biggest issue I have come across with alloy wheels is not with the nuts seizing up, but the wheels corroding onto the hubs.