Wheel Nut Torque

Not an easy one.

Firstly, even the torque of the wheel nuts varies on similar vehicles. Eg, if you have a Ducato originally fitted with 15” wheels, the bolts will be M14 where as 16” wheels are M16. I forget the torque settings but I think they are 150Nm and 180Nm. ( I have a note in my Ducato for mine.)

To undo them, it generally will be more. I remember this being demonstrated in metal work at school with one of those ‘bending bar’ torque wrenches. How much more is variable. On an old, seize, thread, lots more. On a new one, not as much more.

I bought a battery powered wrench recently which claims to cope with 400Nm. I wouldn’t use it for tightening - I carry a torque wrench in the Motorhome for that. ( In the cars I really on the supplied tools. The MH is a heavy beast plus we tow a trailer.) I used it on my a wheel on our trail- which was to hand- and it didn’t struggle at all.

When I had Air Assist Suspension added to our previous motorhome, the fitter used one. It undid the wheel nuts and U bolt nuts as if they were finger tight. I noticed it labelled 400 Nm.

Thanks; that helps, Brian. It would be nifty if there was a general rule of thumb one can employ here. Like for example, take the figure of the highest torque from the vehicle's handbook and look for a gun which has say double that much undoing power. But I know of no such rule. :(

Your choices are:

You can break a stud by pushing it past the yield strength.

A tyre iron provides one level of torque.

The torque wrench usually has a longer handle, and that's what you use when putting the nut back on. The web has a table of torque values, all the wheels on Honda use the same torque setting, on your hand-torque-wrench.

You can fit a breaker bar over the tyre iron. The tyre iron has two "nubs" that stand out. They happen to exactly fit the diagonal dimension of some square tubular steel pipe. That pipe gives you more leverage than even the torque wrench.

DO NOT jump on the breaker bar. It's for arm strength and rotational motion only. We broke off two studs on the pickup truck while attempting to jump on the breaker bar.

The reason rotary power tools are used in a tyre shop, is the speed of getting the job done. The purpose is not twisting the stud so much that it yields and snaps off. When a goon sets their power tool to infinity, another mechanic will notice that the brake disc is now warped and he will "identify that a goon did this". The individuals who work in the industry, recognize each others handiwork.

In a video I watched, of a cradle replacement on a car, that Mechanics Butter is just amazing. You expect any threaded things on the underneath of cars, to be good and rusted, and the Butter got all of them.

Paul

On 26/01/2026 01:34, Paul wrote: D

What is Mechanics Butter? I thought that it might be a Canadian/US thing but after a web search I'm none the wiser.

The video I was watching, never showed the container or in fact, the helper applying the stuff. Two people were working on the car, and only the presenter showed progress as the car came apart.

it is most likely to be a phosphoric acid compound, with perhaps additional solvent or gel of one sort or another added. Like naval jelly (the term used when such a substance is used in a boat yard), it's a rust antagonist. It temporarily reverses a ferric oxide. But by doing so, the metallic bits, as soon as they're rinsed off and the least bit exposed to air/water during rinse, a fine rust forms instantly (flash rust) on the large surface area of the freed up metal. So as promptly as the phosphoric acid goes away, the rust comes back. But it's not structural rust particularly at that point, and it may not completely impede nut removal.

The idea is, that material has to follow along the thread path to free up the rust holding the nut on. It should not really be an instantaneous process, but the video I was watching compressed time so the interval for it to soak in was not documented.

If I knew the brand or product details, I would have used that in a description instead.

You can see some of the alternate brews people use for getting rid of the phosphoric.

Paul

This is the current version of what I used in the UK fifty years ago:

It's not just the cordless tool that makes a difference - you may/will need to invest in a impact sockets.

Slightly OT - when I'm out volunteering with the Dales National Park Rangers they use cordless impact drivers to put coach screws into gateposts when fixing furniture to them.

It's not just the torque, it's the vibration as well that drives them in so easily.

Also, what's the difference between a driver and a wrench? Screwfix seems to think that they are separate categories.

I suspect, based on something an experienced mechanic told me many years ago, the secret when undoing a really tight bu**er is the initial ‘shock’.

Back then, air tools were the weapon of choice and he explained they give a ‘short, sharp, shock’ which breaks the stiction. He also said, using a long lever and applying force for too long was more likely to snap the bolt / stud.

I’ve followed his advice for nearly 50 years and don’t recall one ever snapping.

As for a ‘rule of thumb’, not sure. I suspect mechanics may have one but equally there must be a raft of variables which could throw a spanner in the works ( pun intended). Corrosion, lubricant, thread lock, temperature, metal types, …..

So it might have been a name made up by the presenter.

I've used a phosphoric acid based rust removed for years, but never to release a thread which is rusted-tight. It might be interesting to try it and maybe 15 minutes later something like WD40. If that doesn't work perhaps try it in reverse.

I think they call guns that take 1/2" sockets "wrenches" and "drivers" are the low power ones that accept hex shank bits. I believe that's what they've done anyway.

Yeah, I'd be happy with something which could undue nuts done up to that figure. I'd have *guessed* - and it is only a guess - that

Or "Paul" himself. OP: "Anyone know how much power a cordless torque gun needs to undo a stubborn nut?" Paul: "No, but there's this stuff called 'mechanic's butter' which is very good." Jeff: "Can't find anything on the net about it. Are you sure that's what it's called?" Paul: "No, I just made it up." OP: "Any idea of an answer to my original question?" Paul: "No. I just wanted to mention this stuff I saw being used once."

There are some that take both. Bosch make such devices. John

whats the point ? you could easily find an adaptor

The point is that you don't need an adapter.

The 1/2" ones for bolts supply more power and torque, while if you used one of those for driving screws you might cam out the head or snap the screws - impact drivers are screwdrivers, impact wrenches are wrenches.

Theo