Wheel Bolts Lubricate? & Torque

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T5R+

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What is the consensus on applying, eg Copperslip, before refitting alloy wheels? Assume preferential to oil or grease.

Also anyone know the correct torque settings for (21" AMG) rims onto an ML W164.
 
What is the consensus on applying, eg Copperslip, before refitting alloy wheels? Assume preferential to oil or grease.

Also anyone know the correct torque settings for (21" AMG) rims onto an ML W164.

Not sure if i have ever seen a wet torque value recommended for wheel bolts. I have never bothered to lubricate them myself and never had any issues.
 
The official directive is do no lubricate, instead clean threads with wire brush and tighten to specified toque.

Some prefer to use a thin layer of copper grease anyway, then compensate by reducing the torque.
 
I've often wondered about this, as in my working life we used threads that had metal to metal seals, used different thread lubricants, and had torque correction figures for each lubricant. Classic example was Shell Nigeria and VAM threads with a reverse 45 degree metal to metal seal between the male and female threads, they wondered why they kept leaking, found it was because they were using a teflon based thread lubricant with a torque correction figure of 0.75 but were making the connection up to 100% of recommended torque, causing deformation of the 45 degree metal seal and thus leakage.

On wheel bolts, I routinely use copperslip on them then make them up to recommended 130Nm torque, and have not had a problem removing them - which either means that copperslip has a torque correction figure of 1 or that my work experience does not apply to wheel bolts!
 
Any form of lubricant on threads whether it be oil, grease, loctite or even that the bolt is plated as opposed to plain steel calls for a reduction in the torque value in order to produce the original specified clamping force.

No question that the official method is dry threads only which is fine in theory but being pragmatic and to reduce the risk of them seizing I have always used a little copper grease and reduced the torque value by 20%.

Frankly for normal wheel bolts it's not a big deal either way but no way will I torque a locking wheel bolt dry or would I let anyone else tighten them but me. If you do otherwise you might as well leave the spare wheel in the garage for all the use it might be out on the road when the locking bolts prove impossible to remove with the cars toolkit. Given the lack of care taken by some in the automotive trade, locking wheel bolts are a poorly engineered problem just waiting to happen.
 
I've noticed that when I watch a garage change my tyres and refit the wheels they will use a torque wrench (nominally set at 100Nm), but if you sit in the office you'll almost certainly hear a rattle gun in use.
 
MB torque settings for stuff like wheel bolts are typically somewhere between 'book' torque values for lubed and dry threads. For example generic torque values for a class 10.9 m12 x 1.5mm bolt are ~98Nm lubed (k factor 0.15) and 131Nm (k factor 0.2) dry. K factors are a guestimate of the effect friction has on the torque vs tension relationship, those torque numbers are for a clamp force around 75% of proof load. Older MBs that use m12 x 1.5 wheel bolts have a torque setting of 110Nm

Newer stuff with m14 x 1.5 bolts can be anything from 130Nm (upto E class size?) to 150Nm for bigger things like S classes and supermarket assault vehicles and probably even higher for some of the vans? Generic dry torque values for a class 10.9 m14 x 1.5 can be up around 210Nm

K factors for copper grease (and other lubricants/anti seize compounds) can vary some by brand... cheap stuff that's mostly clay and oil with a little copper is obviously gonna behave differently to a decent brand that's got 10 - 30% copper powder in it along with similar amounts of graphite

Personally i've never seen a wheel bolt or wheel nut that was properly corroded/rusted into place. Every seized wheel bolt (or remains of when they've snapped) i've seen that got removed with the threads mostly intact showed clear signs of necked/elongated threads and very little rust compared to say an origional suspension bolt that hasn't been touched since the car left the factory and was properly seized from corrosion

Given the relatively conservative torque values (from the wheel bolts POV) there's a fair bit bit wriggle room for doing things 'wrong'. Probably fairly difficult to properly overtighten lubed wheel bolts by hand accidently but a monkey with a rattle gun will overtighten them a chunk more due to the reduction in friction as upto 90% of the torque applied is overcome friction. Probably negating anything copperslip brings to the table and making it more likely that they're tightened beyond yield

Copper grease on the mounting faces is the other common one for people that have had wheels stick to the hub. The joint functions kinda like a clutch in that it's friction between the wheel and hub that transmits forces leaving the bolts to act purely in tension. This is because bending/shear loads on the bolts leads to bad things happening
Wheels only tend to stick to hubs if they're rarely removed and if/when this happens it's virtually always the contact point between the centre register of the hub and the centre/piloting hole in the wheel. In other words don't lather copper grease over the entire hub face, a thin smear around the centre register of the hub is all that should be needed
Also anyone know the correct torque settings for (21" AMG) rims onto an ML W164.

The wheels won't make a difference 99% of the time*, torque values are mostly based on the bolt size and required clamping force. Probably 150Nm for an ML?

* sometimes steel vs ally wheels can, usually due to different bolt seats
 
Thanks all.

Having some wheels refurbished next week or two.

Already painted my "spare" bolts in eager readiness.

Plan to freshen up the calipers when I change the wheels across. Resisting going red.

Plan a thin smear of copperslip between rim and hub.

There always seems to be a debate over "lubricating bolts" - suspect will apply a thin coating and torque to 150Nm. (Trying to justify a new torque wrench :rolleyes: - do not always trust the air-gun-cowboy).
 
Another thing to take into account is that tyre fitters/monkeys tend to use a torque wrench only after they've walloped the bolts up with a rattle gun. The torque wrench (obviously) then clicks to say that it's reached the desired figure, though most times it's in excess of this figure by a large amount which the wrench cannot recognise.

When I get mine back after the wheels have been removed, I always back the bolts off and then tighten them again sequentially to the correct values. this takes less than 5 minutes for all four.

Oh, and I never use any lubricants though mine are removed on a regular basis...
 
I think hotrodder has given the best explanation of the issue and short of gross negligence you would be very unlucky to get in trouble with wheel bolts although it does happen.

I would argue the wriggle room does not apply to locking bolts because it's not the thread or shank that is going to fail first, it will be head or the key. If they are overnighted or seize in place at best you will not be able to remove them at the side of the road when you need to and at worst they will be damaged and need specialist removal. I've been there and suffered at the hands of an idiot with a rattle gun.

The instructions that come with locking wheel bolts will state in big bold text "On no account must these bolts be tightened with an impact gun" or words to that effect but who reads instructions.
 

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