Wheel stuck to hub

[damian9128]

You're thinking too hard.Just leave it, if another gets stuck just call the AA out again haha!

[Number_Cruncher]

The snippet from Mitsubishi is true - for those (commercial?) vehicles covered by that bulletin. It's not necessarily true for any other vehicle.

It is technically true that lubrication does reduce scatter in axial tension values - but, as pointed out by Rory, this is no use to you at all if grease, oil, or whatever is not specified by the manufacturer when they determine the torque you must apply. The bolts may be more consistently tensioned with some lubrication, but, they'll be consistently at the WRONG tension!

The information provided by Roger Jones is much more applicable to our cars - possibly there is newer guidance on WIS.

Greasing the face between the hub and the wheel is also really bad news. This face acts as a clutch, and is how all the drive and brake torque *should* be transmitted between the wheel and hub. If you grease this face, the "clutch" can slip which places the bolts under a bending loading they were not designed for. This slip is more likely under hard driving conditions.


People tend to get away with this ad-hoc wheel mounting procedure on cars because manufacturers design in a lot of redundancy for this kind of amateur abuse rather than it being in any way best practice.

[goldestate]

My point is the "Chinese Whispers" that have led to this mixed opinion on the matter.
The Mitsibishi document was merely used to highlight the thinking behind such a seemingly simple operation, clearly the similarities are there between trucks and cars.
I used to use copper grease but now I don't I simply hadn't thought it through and had probably picked the idea up from someone else.
My current stance is that lubricating the mating surfaces of the bolt/nut and wheel is something I will not do, but I will lubricate with high temperature paste (ceramic stuff for the pads) the threads and the central wheel to hub mating surfaces.
Until Ross Brawn drops in and tells me different I will carry on.

[Number_Cruncher]

>>My point is the "Chinese Whispers" that have led to this mixed opinion on the matter.

Yes, I agree - it's shocking just how many aspects of vehicle maintenance are so poorly controlled. The manufacturers are usually pretty clear, it's just that every garage contains mechanics who think they know better, and think they can just make it up as they go along.


>>Until Ross Brawn drops in and tells me different I will carry on.

Why? Do you run one of the cars he designed? No? Didn't think so!

If you run through the calculations of how much torque the friction face between the wheel and hub can carry, you'll soon see that it can easily slip under heavy braking, which is an undesirable situation.

(No, I'm not Ross Brawn, but I've designed and rectified the faulty design of enough safety critical bolted joints to be able to talk about the subject!)

[goldestate]

Blimey I didn't preach, I merely highlighted the contradictions expressed on here,
I have always greased liberally and now I have changed (albeit slightly).
The Mitsubishi document just seemed to make sense to me, they have some world class engineers.
I suppose it stems from struggling to remove wheels at the side of the road.
The Ross Brawn quip is due to his new Mercedes F1 Role where I freely admit I probably wouldn't make tea boy.
I suppose his TWR days may have led to some road car influences but no I don't drive one (and never have)

[Number_Cruncher]

Sorry if my reply was a little blunt.

>>The Mitsubishi document just seemed to make sense to me, they have some world class engineers.

Yes - the Mitsubishi document is fine - for those Mitsubishis only.

Roger Jones has posted the relevant info for Mercedes cars higher up the thread.

I know there's a difference in the traditions and history of the different types of vehicle maintenance, but, would you be happy on the runway in a Boeing to find the mechanic who had just fitted the wheels had followed an Airbus procedure? I fiond it really strange that one of the most safety critical fasteners on the car is being approached with such a laissez faire attitude - this is on a forum where people agonise over the choice of polish and cleaning cloth!

Wheel bolt failure tends not to be such a big issue on cars, as the safety margins in the design are usually large enough to cover bodging, but, commercial vehicle wheel security, and the confusion caused by lube / no lube advocates continues to cause serious accidents.

Have a nosy on the ground on the run up to fast roundabout junctions when you're next in a traffic jam - you won't have to wait long before you see a failed heavy vehicle stud and nut rusting in the verge.

>>I suppose it stems from struggling to remove wheels at the side of the road.

Yes, it is problematic. However, if the wheels are removed and cleaned at reasonable intervals, especially after any wading, it shouldn't cause much difficulty.

[renault12ts]

So...the answer is clean your nuts and bolts and mating surfaces and torque to the recommended values without grease or oil.

[lynall]

Ive been a truck mech for over 20 years and can tell you this, if i could get my hands on the people who fitted the wheels i struggle with daily because they didnt lube the studs they would be in big trouble.

I had one last week that i had to heat the wheel nuts with the oxy torch as the 1" air gun wouldnt touch them, all because fitted up dry.

The official line with trucks is a small amount of engine oil on the stud and a small amount of engine oil between the nut and built in washer, then i nip them up with a 3/4 air gun and finish them off with the 3/4 torque wrench

Problem with trucks is we are still using the same size and number of wheel nuts for ever and the weights have gone from 32 to 44 ton in the time i have been doing this job.

On all the cars i have ever owned its copper grease on the hub face and either some oil or grease on the wheelbolts and i have never ever had any problem.

If wheel face or hub corroded they should be cleaned up with emery or a wire brush.

I should add i give my car some stick now and then and ive never had any bother with hub/wheel slip, i wonder if 210 e55 350bhp has same size bolts as e200 150ishbhp bet it has!



Lynall

[lynall]

Wheel bolt failure tends not to be such a big issue on cars, as the safety margins in the design are usually large enough to cover bodging, but, commercial vehicle wheel security, and the confusion caused by lube / no lube advocates continues to cause serious accidents.

Have a nosy on the ground on the run up to fast roundabout junctions when you're next in a traffic jam - you won't have to wait long before you see a failed heavy vehicle stud and nut rusting in the verge.


I think thats just scare mongering as i cant remember the last time i saw or heard of a wheel loss incident on a commercial vehicle.
In my job i certainly come across a few odd loose nuts not falling off loose but not torqued coreectly, which can almost be put in the laps of either tyre fitters but mainly the drivers not checking the nuts daily!



Lynall

[buccal]

Had a nightmare with his last year, 2am frozen to the bone, no torch and wheel completely fused to the hub.

Please be very careful if you boot it repeatedly, we nearly had a disaster with the jack

[Number_Cruncher]

>>a small amount of engine oil on the stud and a small amount of engine oil between the nut and built in washer

Lynall, I've been around trucks for long enough to regard those nuts and the spigot mounted wheels they are used on as modern! I can well remember many stud failures, and thankfully a smaller number of complete wheel loss incidents. If you look at the official VOSA figures, commercial vehicle wheel loss remains a problem.

Stud failure was so common, we kept them in stock!

>>i wonder if 210 e55 350bhp has same size bolts as e200 150ishbhp bet it has!

It's actually an emergency brake application which is most likely to cause slip, and so, both vehicles will produce remarkably similar brake torques before the wheel slips, and hence, the same design of wheel bolt is applicable for both.

[wemorgan]

Just on a point of engineering, to what % of ultimate tensile strength are wheel bolt torqued to?

I've only done a few hand calcs myself, so no expert by any means. IIRC the bolts I evaluated were torqued to 80% of UTS. The failure criteria was such that the shear forces were 50% of the axial forces. So I could well imagine that an over torqued bolt would more readily fail under shear if the contacting surface was slipping.

I greased the surface of my wheels only the other week. But now having read this thread and thought about it I'll be remove the grease next w/e.

[jasonyw]

Characteristic of Merc wheels, it happens all the time no matter how clean you made it. It stuck because the inner most bit of the wheel mated to the hub. You may call it Merc bad design. I have to use the plastic mallet most of the time removing the wheels for cleaning after the winters.

Never happened before when I was a Ford or Nissan driver.

[Will]

Looking at this slightly differently - I wonder what the greater risk of injury is though:

- Wheels coming off cars because the bolts or hubs have been greased

Or

- People injuring themselves trying to remove seized wheels from jacked up cars?

I guess there's a greater chance of cars falling off jacks or people sustaining minor injury from struggling with seized wheels, although I appreciate that a greater accident could result from a wheel becoming detached.

Wouldn't all five wheel bolts have to snap at once for the wheel to come off though?

Will

[Number_Cruncher]

Originally Posted by wemorgan

Just on a point of engineering, to what % of ultimate tensile strength are wheel bolt torqued to?

I've only done a few hand calcs myself, so no expert by any means. IIRC the bolts I evaluated were torqued to 80% of UTS. The failure criteria was such that the shear forces were 50% of the axial forces. So I could well imagine that an over torqued bolt would more readily fail under shear if the contacting surface was slipping.

I greased the surface of my wheels only the other week. But now having read this thread and thought about it I'll be remove the grease next w/e.

If installed dry, they produce axial stress which is about 60% of yield (assuming 10.9). A high performance joint which was designed using lesser margins would, typically, be torqued up to 80% of yield, while higher performance still would use a torque plus angle specification.

I would be very worried about wheel bolts at 80% of UTS - this is perilously close to yield - for a bolt which is desgned to be removed for service, you can't go so close to yield, as obviously damage is being done to the bolt.

Off axis loading is very damaging for bolts, especially in fatigue. I've seen bolts fail rapidly after thread repair where the helicoil wasn't inserted at 90 degrees to the plate - very embarrasing as I had specified the thread repair, but hadn't given a tolerance on the orthogonality of the hole which was drilled through - I had assumed that something reasonable would have been done using a mag drill, and what I found was fitters in the depot doing the drilling by eye!

As a practical point, we've just had to buy an old Audi (SWMBO had an incident with her Astra in the snow), and I'm going to have to buy it a set of wheel bolts as the previous owner / mechanic has wrecked them with copperslip - one or two of the bolts have *visible* necking where bolt has stretched.