My last boss refused to put alloys on any of our new trucks for a similar reason, Rutland. He always said you never got a true mating between the wheel and hub and that the wheels came loose over time. Obviously a truck wheel is lethal when coming off.

It is probably less about the mating issues and more about the dissimilar metal corrosion OldShep... part of the problem is that when you have the tyres/garage folks change wheels they will not normally clean off the two surfaces with a wire brush. Using grease is OK but only in moderation......

and I will not allow folks to do up my wheel nuts with an air wrench either (which tends to distort the nut cover so you can't get a normal wrench on either). Last time I asked this they tightened it up 'manually' so much that when it was time for that wheel to come off the next garage needed a 2m breaker bar to crack them (I am not kidding...).

Anyway I now carry a full range of stuff in my P38: 3/4" breaker bar - 24" long - and 27mm sockets etc.... and I lightly lube the nuts with WD40...

Forgot to add something: If you remove brake dust build-up off your alloys using the 'acid' type cleaners it makes the dissimilar metal corrosion on some makes even worse !...

Not sure I have seen many trucks with Alloy Wheels in the UK in fact but will assume it is also a strength issue....(?)....

Given the number of folk who, like me, do use Copaslip on wheel studs, bolts and flanges if there really were a problem you'd know. Wheels would be falling off by the truckload everywhere! Obviously not so the whole thing is clearly a non issue in practice despite the multitude of folk enjoying themselves arguing about it on t'net, in the pub and on garage forecourts.

I know actually looking up the relevant engineering data is cheating but a quick look at the Copaslip short form advertising data sheet illustrates the point.

The short form of the standard thread equation relating torque to clamping pressure in metric units is T = KDP
where T = Torque (N.m), D = Diameter (m), P = Clamping force (N), K = Nut factor. For practical purposes K is the co-efficient of friction between the two threaded components. Certainly so in this case.

The Copaslip data at :- https://www.molyslip.co.uk/products/anti-seize-and-assembly/copaslip/ has list of K values for for several materials coated with Copaslip. Steel on steel as would be appropriate to wheel nuts is given as 0.12.

The Roymech website at :- http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm includes a useful table of coefficients of friction for threaded steel fasteners. Generally 0.12 to 0.18 for mechanic cleaned steel fasteners so not vastly different to Copaslip coated ones. Certainly the maximum 6 % difference is well within the safety factors of rational engineering for load carrying structures. Basically all Copaslip will do is to stabilise the co-efficient of friction at the low end of normal range. What may be surprising is how little difference lubrication makes to the measured figures. Reason is that pressures in the thread of any reasonably tight joint are so high that any normal liquid phase lubricant is squeezed out of the load bearing side so its near enough pure metal to metal contact. Of course the moment the pressure is released the lubricant can get back in so the nut spins on really easily. Bit different if you use a solid lubricant such graphite or moly powder. Some of the modern synthetics have enough extreme pressure performance to really upset things too.

Perhaps surprisingly Copaslip is only around 15% copper, the rest is a thin oil with thickening agents so it behaves like grease when not under pressure. When put under pressure the carrier squidges out so the joint is made via a very thin layer of pretty pure copper. More or less a mechanical plating process. The anti size properties come from the relatively low shear strength of pure copper allowing the "plating" layer to shear if everything else is gummed up.

Realistically, unless you put stupid amounts on so the carrier can't squidge out, Copaslip makes no difference.

Clive

Hmm, all interesting stuff. I wouldn't argue about it and I know some people always use it. I never have except on that one occasion about 25 years ago when I did and within 10 miles the wheel had come loose so I never have since. I may have been over generous with it and put too much on or I may not have done the bolts up as tight as I should but it put me off using it. I have sometimes dunked wheel bolts in used sump oil if they are tight on the threads but that is about it (I'll probably find now that is a complete no-no too).

Ordinarily the only time the Copaslip comes out these days is on brake pads, even though most modern ones come with an anti-squeal coating so it probably isn'y necessary, brake caliper sliders and to slobber in grotty old bulb holders to give better conductivity rather than having to thump a light to make it come on.

Jeez, this is getting heavy, , as Richard said, you never forget that one time the wheel came loose. let’s just accept we all treat our wheel bolts/nuts differently,
Wether it’s using a torque wrench, breaker bar or a gun to put them on, it’s how you feel safest at the end of the day.