Wheel nuts - Copper grease or not?

[Rich]

I'm sure I've seen a post where Tony says he doesn't use it. I do though but wondering if I should be?

[scorps]

I've never seen a garage use it.

[CIH]

No. Don't grease up any safety crital thread which has to be locked down to hold something on. (unlike, say, the intrnal threads of a tie rod for example.)

[Rich]

Interesting, I've been using it for years! The nuts for the steel wheels are bone dry though, won't this make removing them a PITA?

[Tony]

It's a big "NO"

 

If there's corrosion on the threads clean it off, but you must not grease the bolts/ studs.

 

Why

Any fluid between the threads will deceive factual torque values.

[Rich]

So what about caliper, pinch bolt, wishbone bolts etc can you grease those as I also do this?

[Tango]

If you do then you need to adjust the torque figures according to what you lube with. I have a chart somewhere with the reduced torques depending on coatings used, e.g. Xylan dry coated, zinc coated, greased, etc.

The risk without doing the adjustment is to over torque and cause the bolt material to exceed it's elastic limit which can result in 'waisting' or 'necking' of the bolt diameter.

Of course this depends on the ultimate tensile strength of the bolt material so varies if they are stainless steel, high tensile, or 'standard' alloy steel.

So unless you have all the info it's best to use the OEM recommended figures which are based on the fasteners being clean and dry (unless otherwise stated).

[Tony]

I was just going to say all that

[hms]

One thing I didn't realise was that if the wheel nuts are exposed then use wheel nuts that are blind drilled, i.e. the hole does not go all the way though, as that protects the thread.

A wheel nut with the thread going all the way through is meant to be covered by a hub cap or somesuch to protect the exposed thread from the elements.

h

[Rich]

If you do then you need to adjust the torque figures according to what you lube with. I have a chart somewhere with the reduced torques depending on coatings used, e.g. Xylan dry coated, zinc coated, greased, etc.

The risk without doing the adjustment is to over torque and cause the bolt material to exceed it's elastic limit which can result in 'waisting' or 'necking' of the bolt diameter.

Of course this depends on the ultimate tensile strength of the bolt material so varies if they are stainless steel, high tensile, or 'standard' alloy steel.

So unless you have all the info it's best to use the OEM recommended figures which are based on the fasteners being clean and dry (unless otherwise stated).

 

Thanks for the explanation. So what causes it to over torque, the nut will move further due to the lubrication?

 

 

One thing I didn't realise was that if the wheel nuts are exposed then use wheel nuts that are blind drilled, i.e. the hole does not go all the way though, as that protects the thread.

A wheel nut with the thread going all the way through is meant to be covered by a hub cap or somesuch to protect the exposed thread from the elements.

h

 

The nuts for my steel wheels go all the way through and I'm planning on having them exposed but I always torque them correctly, they aren't blasted up with an air gun!

[Tango]

One thing I didn't realise was that if the wheel nuts are exposed then use wheel nuts that are blind drilled, i.e. the hole does not go all the way though, as that protects the thread.

A wheel nut with the thread going all the way through is meant to be covered by a hub cap or somesuch to protect the exposed thread from the elements.

h

 

I tend to grease any exposed threads wherever they are on the car for that reason, but only after torquing. Where it's not practicable to torque fasteners I'll use copper slip grease before make up, especially where the joint is subject to heat like on the exhaust system.

Last week I had to drill out 5 of the six 5mm bolts holding the dummy tailpipes to the rear valance of the IS-F. Needless to say after tapping out the threads the replacement bolts were well coated with copper slip.

 

Couldn't load the chart, but here's the info on reduced torque values.

LUBRICANT OR PLATING...............TORQUE CHANGES

Oil...............................................Reduce torque 15% to 25%

Dry Film (Teflon or moly based)......Reduce torque 50%

Dry Wax (Cetyl alcohol) ................Reduce torque 50%

Chrome plating............................. No change

Cadmium plating................... ........Reduce torque 25%

Zinc plating....................................Reduce torque 15%

[Tango]

Thanks for the explanation. So what causes it to over torque, the nut will move further due to the lubrication?

 

 

Another point is the recommended torque values for torqing nuts are usually higher than that for the equivalent size of bolt because of the increased friction between the nut and the mating surface.

To achieve the correct tension in the bolt or stud, a load has to be applied that stretches it within its elastic limit. If done correctly the bolt/stud returns to its original length when you take the tensile load off (undo it). Under-torquing means you haven't applied sufficient load to tension (stretch) the stud or bolt, so it's likely to loosen. Over-torquing is when you apply so much load that the bolt/stud stretches beyond the ultimate tensile strength (UTS) of the material it's made from, and results in breakage or a bolt/stud that will not return to its original length (the diameter of the thread is usually reduced somewhere along its length.

 

The torque value is estimated on the friction between the fastener and it's mating part based on the coefficient of friction between the mating materials. A dry make-up has a higher coefficient of friction value than a lubricated one (will also vary depending on the type of lube) so applying the torque load for a dry make-up to a lubed fastener will increase the tension/take the fastener nearer to exceeding its UTS.

 

A crude way of estimating torque value applied to a fastener when you cannot get a torque wrench on it is to use or make up a joint with the same clamp length then measure the rotation from hand tight using the torque wrench, then apply the same rotation to the inaccessable fastener using a spanner (so yes Rich, over torquing will move the bolt or nut further due to lubrication).

[SteveOC]

I did some searching on this topic and have avoided using anything on wheel bolts/nuts as a result but as may be seen on my other thread, the downside 'may' be a greater propensity for things becoming 'seized'.

 

I nervously removed my wheel nuts on the MX5 just now, having sorted out the Volvo, and they came off with relative ease - and on close examination I found that the locking nuts had copper slip/grease on them whilst the standard nuts did not. I don't know when this was done or by who but assume it was done by the previous owner or his/my Mazda dealer as it was all 4 nuts on all 4 wheels and nobody but Mazda have removed all 4 wheels in the last 4 years.

 

So, should I remove the grease and also what is a recommended torque setting for the bolts - I guess I should have asked whilst I was at WIM/BB getting tyres but didn't think?

 

Steve O.

[tunnie]

Sorry for dragging up old thread, but read with interest as I do put a little copper slip on the wheel bolts. Not on the thread, but on the flat surface to stop it sticking to the wheel. I also put some on the wheel hub to stop it sticking on. (had it before where wheels are stuck fast)

 

As long as you avoid the thread is it ok?

[CIH]

Sorry for dragging up old thread, but read with interest as I do put a little copper slip on the wheel bolts. Not on the thread, but on the flat surface to stop it sticking to the wheel. I also put some on the wheel hub to stop it sticking on. (had it before where wheels are stuck fast)

 

As long as you avoid the thread is it ok?

 

Where the wheel mounts to the hub isn't a bad idea. Not unusual for alloy wheels to be stuck on, or older steelies to rust insitu.