Wheel stuck to hub

[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]

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.

 

[wemorgan]

Sorry, my previous post was incorrect. I meant 80% of yield, not UTS.

 

[Number_Cruncher]

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

Once one has broken, all the load is borne by 4, then 3, then, 2, then 1, and bang! As each bolt breaks, the stress on the remaining bolts increases - if the bolts are closer to breaking because they've been over stretched, then they'll ping off fairly rapidly.

It's usually a design case to demonstrate the adequacy of a bolted joint with one bolt missing - this would be a demonstration via calculation, and would assume the rest of the joint is absolutely nominal - i.e., no dodgy greasing!

So, without greasing, you have a joint which should survive losing one bolt, and after greasing, you may have created an unstable scenario where the loss of one bolt will more readily progress to the loss of the whole wheel.

 

[flango]

So...the answer is clean your nuts .

I always clean my nuts thank you

 

[Will]

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

Once one has broken, all the load is borne by 4, then 3, then, 2, then 1, and bang! As each bolt breaks, the stress on the remaining bolts increases - if the bolts are closer to breaking because they've been over stretched, then they'll ping off fairly rapidly.

It's usually a design case to demonstrate the adequacy of a bolted joint with one bolt missing - this would be a demonstration via calculation, and would assume the rest of the joint is absolutely nominal - i.e., no dodgy greasing!

So, without greasing, you have a joint which should survive losing one bolt, and after greasing, you may have created an unstable scenario where the loss of one bolt will more readily progress to the loss of the whole wheel.

Yep - that makes perfect sense, obviously less bolts taking the force will be under greater stress than more

I guess I'm thinking that the initial instance of one bolt breaking would then have to be followed by an immediate second incident of a fourth wheel bolt breaking straight after (I appreciate this is a more likely as it's under greater strain) and then all the rest of them one after another immediately afterwards? Does anyone know how often has this happened?

Although I can see this *could* happen, am I right in thinking that even when the wheel bolts and hub have been greased, it'd be a very rare scenario?

No way am I questioning the calculations behind this, just wondering how often it has happened in the real world bearing in mind how many cars have had the wheels/hubs/bolts greased over the years (like your wife's new Audi )

Will

 

[Number_Cruncher]

The number of wheel loss incidents is a good question. Unlike trucks, I don't think the data are kept.

I don't think it's a massive problem - as mentioned, these bolts on cars are designed with a big margin because the makers know that people will deviate from the correct procedure.

One high profile case - I wonder if the SIARPC on Top Gear had its hub and bolts greased?

Commercial vehicle losses are in the region of a few hundred each year. I imagine that wheel loss on cars due to poor or complete failure to tighten the bolts will dominate over failures caused by grease.

However, the broad point remains - we fuss over whther to use 229.3 or 229.5 oil, we worry about swirl marks in the paint, and the colour of the hub centre caps, yet many are happy to make up the safety critical stuff as they go along. This is crazy!

 

[Will]

Thanks - some good observations there

I guess it can't be a massive problem for cars as we'd probably know about it after all these years. As you say, probably more people lose wheels for other reasons such as slack/missing bolts/nuts.

I do wonder about my question on the previous page - how many accidents are caused by people struggling with wheels on jacked up cars? Bearing in mind that so many people have experienced seized-on wheels, I suspect there must be quite a few!

Will

 

[yachtman]

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

Once one has broken, all the load is borne by 4, then 3, then, 2, then 1, and bang! As each bolt breaks, the stress on the remaining bolts increases - if the bolts are closer to breaking because they've been over stretched, then they'll ping off fairly rapidly.

It's usually a design case to demonstrate the adequacy of a bolted joint with one bolt missing - this would be a demonstration via calculation, and would assume the rest of the joint is absolutely nominal - i.e., no dodgy greasing!

So, without greasing, you have a joint which should survive losing one bolt, and after greasing, you may have created an unstable scenario where the loss of one bolt will more readily progress to the loss of the whole wheel.

As a youth I was walking home one day, lorry went by, followed by a large bang, a wheel nut & 1/2 a stud shot in front of me, lorry went on 20 yards, followed by another bang, 5 yards followed by another bang, the rest followed within a wheel revolution!! Dust and nuts everywhere. Truck dropped to its axel and wheel carried on, through a garden fence

 

[lynall]

Yachtman as a youth, how many years ago was that

Number cruncher i can see your point but a few hundred is a bit vague got any more accurate figures?

I remember when the wheels were held on with the conical nuts and the left hand thread set up, mind you they were old hat when i started but still plenty around.

Try a google for the IRTE recomended wheel fitment guide as they also say use a small amount of engine oil on studs, unless of course they have changed it!

But i can say hand on heart in over 20 years i have never personally had a wheel loss incident, and when i ran a commercial workshop for approx 10 years also never had one all using the same procedures that i still use to this day, in fact did a customers truck last night same way as ever.

Which i should say was taught to me by my father law who is now 72 and was a right stickler for lubing his nuts




>>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.

As the e55 has absolutely huge brakes compared to the e200 shouldnt the e55 be more prone to the slip problem?

Also worth bearing in mind the w210 range have fantastic brakes as std so the amg versions must be amazing.

Ps no stories about Gardners or oil leaks


Lynall

 

[Number_Cruncher]

I'll see if I can dig the numbers out.

I think the IRTE are on dodgy ground giving blanket advice like that. They can't possibly know what each manufacturer recommends.

Wheel mounting and check torquing was a real PITA about 30 years ago, because there was the maximum overlap between the old SMMT taper nuts set up, and the "new" spigot mounted wheels. Approaching a vehicle to check the wheel nuts meant knowing the torque, and whether the passnger side was left hand thread - this could be different between tractor unit and trailer too! We had enough trouble with this confusing set up to ban our drivers from touching them at all, and only workshop staff were allowed.

Without going into Gardner engines and oil leaks, we did struggle the first time we took the wheels off the back axle of a Scammell Constructor 8, which was one of the first Leylands with spigot mounted wheels. We ended up having to place bottle jacks between the chassis and the rim, and jack the wheel out bit by bit, turning between each push.

As for the W210s, maximum brake force is limited by tyre to road slip - the size of the brakes inside the wheel are truly irrelevant.

In some cases, fitting larger front brakes can actually reduce the total stopping power of the car - though I suspect the "Max Power" brigade will never understand this.

 

[geoffd]

just another twist

What an interesting thread. Thank you for the engineering and trade insights. Truly educational. But...

How many of us use a torque wrench on wheel bolts ? And how many of us check bolt torque after other people have meddled with our wheels ?

Is this more or less likely to damage bolts by overtightening than is the use of lubricants ?

Geoff

 

[Rory]

How many of us use a torque wrench on wheel bolts ?

I do, but for many years just did them up to what seemd right.

As I mentioned earlier, compared to jumping up and down on a wheelbrace to tighten them, it surprising how "untight" they seem when done up to the correct torque.

 

[Number_Cruncher]

For heavy goods vehicles, the numbers can be found here;

http://www.dft.gov.uk/pgr/roads/veh...eldetachment/yvehiclewheeldetachmentr1727.pdf

Here's a snippet;

"The various studies carried out produced quite variable estimates of the frequency of wheel fixing problems. However, with the exception of the TRL driver survey, there was general agreement that the frequency of loose or missing wheel nuts is in the low thousands each year, the frequency of wheel detachment is in the low hundreds each year and that annual fatalities resulting from wheel detachment are likely to be in single figures."

 

[lynall]

Asked my comrades in arms at work last night about their experience with wheel nuts over the years, between us well over a hundred and fifty years of slovenly workmanship

General consensus was that i am to fussy never but almost every heavy truck we could think of had exactly the same size wheel nut and bolt combination apart from Scanias with have a much coarser thread.

Hence the blanket advice i mentioned in an earlier post ref lube nuts and bolts.



Lynall

 

[wemorgan]

Asked my comrades in arms at work last night about their experience with wheel nuts over the years, between us well over a hundred and fifty years of slovenly workmanship

and how many cups of tea?

 

[lynall]

Cant say i would get into trouble, but would also be a lot richer



Lynall