Wheel stuck on hub: help.

[scarble]

Yea.. shear. S.H.E.A.R.. I really should know

Anyway, I'm now wondering.. isn't there a lip in the wheel that goes over a flange or something? Or am I being daft?
I genuinely don't know now if the bolts should take shear (which I spelt right).
Any wheel/hub engineers about?
I think the last time I did anything on bolted joint design was at uni

Edited by scarble on Saturday 6th December 12:03

[B'stard Child]

p1esk said:

Hmm, I think I'd like further opinions on that. My suspicion is that the bolts/stubs are what really transmit the torque, rather than friction between the wheel and disc/hub.

I don't think so

p1esk said:

I would have thought that high tensile bolts/studs of the diameters normally used would take a fair combination of shear and tension, quite sufficient to carry the necessary torque.

But they aren't high tensile used as OE

p1esk said:

What happens if the bolts or nuts are not tightened sufficiently to ensure that the necessary friction is achieved? They will then have to carry the load, will they not?

Then the wheel comes loose and you notice a large amount of vibration and then the studs or wheel bolts chaff and eventually shear or fall out - either way most of the time the wheel overtakes you on it's way into the scenery

[B'stard Child]

scarble said:

Anyway, I'm now wondering.. isn't there a lip in the wheel that goes over a flange or something? Or am I being daft?

Not always - some cars don't have them - just plain flat mounting surface.

[FiF]

scarble said:

Yea.. shear. S.H.E.A.R.. I really should know

Anyway, I'm now wondering.. isn't there a lip in the wheel that goes over a flange or something? Or am I being daft?
I genuinely don't know now if the bolts should take shear (which I spelt right).
Any wheel/hub engineers about?
I think the last time I did anything on bolted joint design was at uni

Edited by scarble on Saturday 6th December 12:03

The science of this is that there is a window of clamping pressure where too little pressure allows the wheel to move and shuffle, wears bolt holes and studs and eventually the whole thing becomes a lost wheel.

Too high a clamping pressure can cause distortion but more likely the elastic limit of the studs is exceeded, they plastically deform then the clamping pressure is too little, see first paragraph.

So in essence it has to be greater clamping force than separation forces in cornering, to provide sufficient friction to give acceleration and braking forces, plus not be so large that the elastic limit of the fastenings are exceeded during extreme manoeuvres. A certain amount of the acceleration and braking forces are passed through the rigid assembly of the tightened construction I.e. hub, wheel and fastenings but it's only a part.

In cars this window of clamping pressure is very wide, which translates into torque settings. In large goods vehicles and buses the window is relatively small hence the wheel fitting practice has to be closely controlled. Fixings for heavy vehicles using cup and cone design can, especially on older vehicles, can an almost impossibly small window due to friction. See below.

It's not just a matter of bunging the wheel on and winding up the fixings. Dirt or excessive paint and grease between the mating surfaces can result in loss of clamping pressure. Damaged and in particular dirty threads can mean so much of the applied torque is lost in overcoming friction that again clamping pressure is insufficient. Dirty threads coupled with cup and cone fixings can mean on some vehicles it is impossible to obtain sufficient clamping pressure

Which leads to the advice that best practice is to ensure threads are clean and very lightly oiled. Some argue oiling the threads is not correct as this can lead to loosening fixings. In reality the science and measurements show that it's wrong. Clean mating surfaces, clean and very lightly oiled threads, correct torque, rechecked after some miles is the way to go. Using the correct parts as specified by OEM is of course taken as a given.

Edited by FiF on Saturday 6th December 15:33

[anonymous-user]

I am a fan of good old leverage. Get a decently sized bar or block of wood, find a suitable point on the suspension/subframe to act as a pivot point and lever against the inner sidewall of the tyre. You dont have to go mental in one particular point, Not many people have mentioned the importance of rotating the wheel periodically no matter what method you are using. You're wanting to work it off, not force it.

I have tried most of the methods mentioned in this thread but this is the easiest way to get extremely stubborn wheels off in my opinion

[paolow]

t400ble said:

Right, make sure the car is well supported

Stick a wheel nut back in a few turns so the wheel doesn't fall off and hit the ground

Get under the car, and give the wheel a good few kicks with the bottom of your foot

Job done

I dont know if this has been covered in the other 5 pages - but there is absolutely no way in hell I would be under a car, no matter how well supported giving it that much force. Bearing in mind the average home mechanic will have a pair of axle stands and a jack at best you really would be playing with fire.
There was a case where I live where a guy was doing DIY on his fiesta and was on his back beneath it (the car was on axle stands). Possibly through his working - or possibly just through bad luck the stands ended up insecure and when he went to pull himself out by grabbing the sill he instead pulled the car off the stands and onto him. Grim.

[Mave]

p1esk said:

CrutyRammers said:

TooMany2cvs said:

p1esk said:

Is the transmission of acceleration and braking torque really dependent on friction between the wheel and hub? I'd have thought the wheel studs took care of that, with the nuts seating into conical areas of the wheel; unless the design details are different these days.

You're right.

Think about the difference in friction between a shiny new wheel on a shiny new disk, versus a manky steel that's been hung under a boot floor as a spare onto a manky near-end-of-life disk.

Capt. Muppet!

An all too common misconception.
The nuts/studs clamp the two faces (the wheel and the hub) together. What takes the load on the wheel is then friction between the two surfaces. The studs don't see any sheer (sideways) load, only tensile load. Studs would bend very easily if you asked them to take the load sideways.

It's the same principle as a clutch, but using bolts/studs instead of springs.

Hmm, I think I'd like further opinions on that. My suspicion is that the bolts/stubs are what really transmit the torque, rather than friction between the wheel and disc/hub.

I would have thought that high tensile bolts/studs of the diameters normally used would take a fair combination of shear and tension, quite sufficient to carry the necessary torque.

Think about the distance from the wheel hub to the conical section of the wheel nut. If the loads aren't being transmitted through friction, then the shear loads manifest themselves as a bending moment into the bolts / studs. Do you think that the bolt / stud diameter normally used are designed to take that shear with, say, an inch moment, as a cyclic load? And if the friction isn't taking the load, what takes the load on brake discs which usually have clearance holes?

[Leptons]

t400ble said:

Right, make sure the car is well supported

Stick a wheel nut back in a few turns so the wheel doesn't fall off and hit the ground

Get under the car, and give the wheel a good few kicks with the bottom of your foot

Job done

I may need a whoosh parrot here but that is horrendous advice.

If it's joke its still retarded because there's always some numpty who'll go and try it.

[silentbrown]

Leptons said:

that is horrendous advice.

+1. Don't. EVER.

Undoing all wheel nuts two turns and lowering it briskly off a trolley jack has never failed me.

[AudiSport]

CraigyMc said:

Hello all,
I'd like to swap my summer wheels over to my winter wheels/tyres set.
I'd be doing this right now if I'd not already started, then hit a probably common snag: one of the rear wheels is firmly glued to the hub, and I can't get it off.

I always put copper grease between them whenever I put wheels on, so I've not run into a situation where I really cannot get the wheel off before.

Any ideas on how to remove it?

For the record, I don't have a big rubber mallet. (Should I get one just for this? Seems overkill!).

Would WD40 down the back of the wheel sort it?
Is there anything I can do involving heating or cooling to get it off easier?

Thoughts please. If I can't do it myself, I'm thinking of driving the car down to the local tyre place and giving them a few quid to swap all the wheels over, which is of course the same as "giving up", and would make me feel bad/annoyed for a while.

Craig

Last time I had this I just pored a kettle of boiling water of the wheel / hub and it came off fine.

[blearyeyedboy]

When you get the wheels off, put some copper grease between the wheel and the hub before you put them back on. Then the next time won't be as much of a sod.

It's because of a similar experience to this that I carry a can of tyre weld as a backup, in case I can't get a wheel off on a hard shoulder. I'm not a small bloke and I've struggled before.

[silentbrown]

The OP said:

I always put copper grease between them whenever I put wheels on, so I've not run into a situation where I really cannot get the wheel off before.

blearyeyedboy said:

When you get the wheels off, put some copper grease between the wheel and the hub before you put them back on. Then the next time won't be as much of a sod.

Wake up at the back, there!

[smn159]

If it's really stuck you'll need another car at right angles, loosened but not removed wheel nuts on the offending wheel and a ratchet strap. Never fails

[blearyeyedboy]

silentbrown said:

The OP said:

I always put copper grease between them whenever I put wheels on, so I've not run into a situation where I really cannot get the wheel off before.

blearyeyedboy said:

When you get the wheels off, put some copper grease between the wheel and the hub before you put them back on. Then the next time won't be as much of a sod.

Wake up at the back, there!

D'oh!

[p1esk]

Mave said:

p1esk said:

My suspicion is that the bolts/stubs are what really transmit the torque, rather than friction between the wheel and disc/hub.

I would have thought that high tensile bolts/studs of the diameters normally used would take a fair combination of shear and tension, quite sufficient to carry the necessary torque.

Think about the distance from the wheel hub to the conical section of the wheel nut. If the loads aren't being transmitted through friction, then the shear loads manifest themselves as a bending moment into the bolts / studs. Do you think that the bolt / stud diameter normally used are designed to take that shear with, say, an inch moment, as a cyclic load? And if the friction isn't taking the load, what takes the load on brake discs which usually have clearance holes?

OK, fair enough, you're making some valid points there, and you're right to mention the bending effect; but I think your one inch moment arm might be exaggerated somewhat, though it depends on the detailed design of the wheel; e.g. the material thickness through which the bolt/stud passes.

Anyhow, I'm not seeking to insist that my understanding of the situation is the correct one: I might be wrong.

Best wishes all,
Dave.

[Mave]

p1esk said:

Mave said:

p1esk said:

My suspicion is that the bolts/stubs are what really transmit the torque, rather than friction between the wheel and disc/hub.

I would have thought that high tensile bolts/studs of the diameters normally used would take a fair combination of shear and tension, quite sufficient to carry the necessary torque.

Think about the distance from the wheel hub to the conical section of the wheel nut. If the loads aren't being transmitted through friction, then the shear loads manifest themselves as a bending moment into the bolts / studs. Do you think that the bolt / stud diameter normally used are designed to take that shear with, say, an inch moment, as a cyclic load? And if the friction isn't taking the load, what takes the load on brake discs which usually have clearance holes?

OK, fair enough, you're making some valid points there, and you're right to mention the bending effect; but I think your one inch moment arm might be exaggerated somewhat, though it depends on the detailed design of the wheel; e.g. the material thickness through which the bolt/stud passes.

Don't forget, the inch moment arm also includes the thickness of the brake disc

(and if the joint is taking the load through the bolts rather than the face, then 1) it would be totally safe to go driving around all the time with the bolts finger tight, providing they don't shake free, and 2) the joint would never stick together because the bolt bending would allow them to microslip every time you accelerate or brake!)

Edited by Mave on Sunday 7th December 09:36

[kev b]

Can the engineers explain (apart from the quantity) the difference between lightly oiled threads and liberally oiled threads?

Surely if there is oil covering all the thread surfaces then any excess will make little difference.

[FiF]

My understanding is that it's meaning oiled as opposed to slathered in heavy grease.

[Mave]

kev b said:

Can the engineers explain (apart from the quantity) the difference between lightly oiled threads and liberally oiled threads?

Surely if there is oil covering all the thread surfaces then any excess will make little difference.

The difference is whether there is so much oil or grease that the thread becomes essentiall hydraulically locked. We normally design for lightly oiled threads, not to reduce friction or prevent seizure, but because the friction is more consistent than dry.

[CraigyMc]

Hi all, OP here.

A few updates:

• I've not become trapped under the car.
• I now own a rubber mallet.
• I'm travelling for work (by plane - car will be staying home) so the next time I get a chance to do this work will be next weekend.

Thanks everyone for your ideas!

Craig