Loose wheels and ATC

[Dustydog]

What was the Al-ko ATC light showing before the journey start and immediately after the accident?
There have been issues that ATC is not fail safe, ie in the event of any electrical event the brakes should not be applied.
See this old thread

Alko ATC jammed / stuck on ... evidently not a 'fail safe' system

A general Google reveals what I mention below to not be uncommon but it searching ATC / ATC stuck and similar variations on this forum yields little, the most promising at first glance being something from 2008 which I chose not to reply to. Basically, we noticed when taking the caravan to be...

forums.practicalcaravan.com

 

[JTQ]

Correct matching of material is most definitely the most important factor regarding the way the fastener retains or does not retain its clamping torque.

Yes of course these are, but my comment was that I did not see the relevance here with the OP's wheel coming off.
So far, the bolt material having in tensile failed, or signs it had, has never been mentioned here as a factor.

 

[Lutz]

Yes of course these are, but my comment was that I did not see the relevance here with the OP's wheel coming off.
So far, the bolt material having in tensile failed, or signs it had, has never been mentioned here as a factor.

Nothing need have reached breaking point for the wheel to have come off. The bolts may simply have become loose because the alloy had exceeded its elastic limit locally, enabling the bolts to rotate to the point where they fell out.

 

[RogerL]

Not entirely true and may differ between cars depending on implementation.

On my car the voltage in the car varied on pin 10 between 0 (engine off) to 14.24 dropping to 12.9 after a few minutes (engine on).

While these voltages might be deemed to be in spec. at the towbar connector, poor wiring in caravans - including mine - can cause further drops. My fridge has a low 12v voltage detection cct. I can't remember the low voltage drop out point and true the fridge has a higher loading than an ATC - none the less my fridge drops in and out if I try to power it when towing. Others have reported the same.

Dodgy wiring in tow bar kits and connectors may also contribute to voltage drops.

There are different implementations of Smart Alternator systems. Some cars have no problems with towing caravans in respect of fridges and battery charging.

Others need work arounds like turning on headlights or air con to prevent the Smart function kicking in.

Other folks fit DC-DC convertors between the car and caravan to restore the voltage back to the required level.

This may not be relevant to the OPs problem but something to consider.

Voltage drop from inadequate wiring is a separate issue to smart alternators.

 

[AndrewAventura]

I've only been towing for 3 years, so if this has been discussed before I'm sorry.
I had a wheel detached and strike a car recently.

I had caravan stored at home on axle stands.
The wheels were free running.
I checked the 130nm wheel bolts as soon as it was on the ground.
On the day of travel I hitched up and did the usual lights, jockey wheel,hitch AND checked the wheel torque again.

These are M12 wheel bolts I guess?

There's been a bit of discussion on other threads about torque wrenches and torque wrench calibration. Are you properly confident in the calibration of yours?

 

[littlebasher]

We bought a new Lunar in 2020 that had the wrong wheel bolts.

They were hopelessly too short, discovered when i replaced one of them to fit a Wraith lock. Dealer posted me a new set that were correct.

There were literally only a few threads engaging in the hub, surprised i even made it home.

 

[Sam Vimes]

Voltage drop from inadequate wiring is a separate issue to smart alternators.

Yes and no. If your smart system is lowering the volts at the towing connector then additional drops across the internal caravan wiring may give problems, as is my case. Without a smart system or at least one like mine the voltage at the towing connector most likely would be high enough to overcome the voltage drops in the caravan wiring.

 

[Sam Vimes]

Some folks fit this to overcome such issues. Look at the product info about cable voltage drop.

Battery to battery charger Caravan BBC1225

Installation instructions Product Information PDF E13 Marking certificate Battery to battery charger Caravan BBC1225 The electrical requirements onboard caravans have increased in the modern world (laptops / tablets / phones/microwaves/hairdryers / Caravan movers etc.). When at campsites this...

sterling-power.com

 

[JTQ]

These are M12 wheel bolts I guess?

There's been a bit of discussion on other threads about torque wrenches and torque wrench calibration. Are you properly confident in the calibration of yours?

A very valid question, given we are told the bolts were torqued to 130 Nm and they were grade 10.9, so if M12 being worked right up and beyond some experts maximum limit.

The maximum limit is massively affected by their own thread condition which alters its friction.

If they were dry and new possibly just about okay, but if lubricated they will have been considerably over tightened.
Lubricating threads, like with oil or copper slip we know some PC forum contributors, even claiming to be "engineers" do, inevitably over tightens them!
Add into that an unknown torque wrench and possibly incorrect use things could easily be damaged. In addition if a previously owned van the bolts could have already have been damaged some time before .

 

[RogerL]

Yes and no. If your smart system is lowering the volts at the towing connector then additional drops across the internal caravan wiring may give problems, as is my case. Without a smart system or at least one like mine the voltage at the towing connector most likely would be high enough to overcome the voltage drops in the caravan wiring.

The smart alternator can't lower the voltage below battery voltage - ATC is designed to work even at that voltage otherwise you could never reset the memory which needs battery voltage for 24 hours.

 

[ProfJohnL]

The smart alternator can't lower the voltage below battery voltage - ATC is designed to work even at that voltage otherwise you could never reset the memory which needs battery voltage for 24 hours.

True a smart alternator cannot lower the battery voltage. Back in history, the power split for the fridge/battery charge was supplied through a voltage controlled relay which in some installations only connected the trailer aux 12V system when the dynamo/alternator was actually generating.

Whilst that technology was dropped some time ago, with the advent of draconian power saving perhaps some car manufacturers have implemented a similar system controlled by software.

I would hope that any car that did this would have either trailer detection system or some control setting that could disable it.

 

[retired ian]

smashing up the bolts, and here they are in the scale of things quite puny and not applied as "fitted shear bolts", just tension loading bolts.

Also the bolts have 60 degree taper and are used to locate the wheel. If the bolts have lost torque, a locking device would allow the bolts to continue locate the wheel.

I agree let's move on.

Of course the other scenario is.
Humble pie moment.
Maybe I didn't locate the wheel properly!
Maybe the ATC was doing it's job, and correcting
the sway!
I'm not shy of admitting errors,(I've made enough in my lifetime)
I joined this chatroom to eliminate ALL possibilities.
There are many members with years of experience, willing to give advice.
And I'm willing to accept advice, or observations.

 

[retired ian]

Just to reply to some of your answers, and a big thank you for your input.

The led was green at start and finish.

The button idea would not affect any functionality, the button would only test the system, " test cycle". All other functions would remain the same.

The bolts didn't break, we found 3 on the road, luckily, I had no spares.

bottom line is:- there is no fail safe on this attachment. Spigot located wheels have extra security.
You could mount spigot type wheel with 2 studs stay on for a long time.
Mounting a wheel without, would possibly travel 100 metres.

I don't know how many car wheels part company.
When was the last time you torqued a car wheel bolt, certainly not twice on every journey.

Positive nut locking would keep the bolts in the tapered seating.

The danger of wheels without spigot:-
No certainty on eccentric running.
As soon as as the bolts slacken off, the wheel becomes eccentric. As this progresses the bolts soon undo , nearside only.

I've seen people argue that, VW beetles and Citreon 2 CVS had no spigot. Not a good reason to adopt a poor 60 year old design.
We have airbags,abs,traction control, radial tyres,split breaking systems,seat belts.crumple zones.


No, I don't have calibrated torque wrenches.
I have 2 with different ranges but 130nm.
Is available on both.
These both agree. Maybe they are both wrong?

 

[Lutz]

I would just like to add a note that the only purpose of a spigot is to make things easier to centre the wheel on assembly to the axle. It has no load carrying ability because, for manufacturing tolerance reasons, it must have clearance to the wheel when the bolts are tightened up,

 

[otherclive]

Apologies if I’ve missed something but I assume that your caravan is not a Bailey from the period when there was a spate of wheel detachments, or that the caravan has OEM wheels and not aftermarket alloys?

WRT your comment on cars. I check my wheel torque after 50 miles from replacing the wheel. But it doesn’t get checked again until the wheel is removed/replaced for some reason. That's a standard recommendation.

 

[JTQ]

Ian, I don't agree with some of your claims, principally as Lutz has just commented, spigots don't secure our car wheels, they aid you mounting the wheel by taking its weight, ideally also allowing you to enter a bolt /nut to centre it.

Clearly in the time it takes for the wheel to part, a spigot takes the radial load, mainly the load carried by the wheel. But it is delusionary to believe this offers any security nor any worthwhile time, the more so with a wheel that is located remote from your immediate driving senses.
Bolt and nut cones are not sized anything near to carrying wheel loadings, so again its wrong to believe they offer that type of security.
I repeat, in our domestic cars the wheel retention for radial loading come from the friction between the wheel and hub, a friction developed solely by the retaining bolt's tension, not from the aligning cone or spheres nor from spigots.

This is anything but "poor design", its only justifiable weakness IMO is having to find a way to hold the wheel weight whilst locating the first bolt, and not that with the 2CV it was a studded hub design. There are however some poor interpretations of it out there!

That you don't recheck your car is down to a combination of poor practice and subtle differences in the details of the bolting system, in part influenced by the design of the wheels.
I do check mine after they have run a short distance post removal, this is down to experience of poor garage practices together with years involved in consulting , designing, along with researching and test challenging bolting systems generally.

Yes, elsewhere spigots are used for load carrying but there we also have to have forced interference fitting well capable of that load carrying and this almost inevitably requires use of hydraulic type forced removal or oil injection type equipment; not your user road side wheel changing.

re the ATC; unless you alter the functionality of it it will continue to do what it does, full on re apply its braking cycle on remaking power; so one way or another the continuity of its power supply must be maintained for it not to do so. Again IMO excellent safe, cost effective designing without the cost and complexity to do otherwise. Designing in complication, cost and lowering reliability is too easy. In this case makes for a product with a low enough cost makers could fit and many caravan owners chose, a very good thing for every body on the roads safety.

 

[Dustydog]

The chap who replaced my tyre yesterday said in 20 years he had never experienced a wheel bolt or nut coming loose after being correctly cleaned and torqued up.

More by years of habit I always check the torque before a long tour but not in between stop overs.
Am I going over the top🤔

 

[JTQ]

The chap who replaced my tyre yesterday said in 20 years he had never experienced a wheel bolt or nut coming loose after being correctly cleaned and torqued up.

More by years of habit I always check the torque before a long tour but not in between stop overs.
Am I going over the top🤔

It would tend to be the person who took the vehicle from the tyre fitter who experienced any wheel retention problem.

Up to a point he is right, if all if prefect the design works no issues, but the world is not like that.
Grease , debris , rust or other corrosion, coating/finishing break down and general aging happens in the interface wheel to hub thread to thread cone seat to socket and the radial loading , extenuated by finding a pot hole, eases things and that vital tension reduces, possibly critically reduces.
That you found a tyre place without any incident in 20 years that they knew of is a big surprise, one I would be fast losing trust with!
I had it from Halfords!!!! The manager's investigations revealed the operative took a phone call, then forgot to go back onto that job, it happens.

No you are not going over the top, and most definitely not with our caravans. A few seconds every few months and just after a wheel removal, who can't afford that investment? Very unlikely you find its needed, but they were not the time it was.

 

[retired ian]

Just to reply to some of your answers, and a big thank you for your input.

The led was green at start and finish.

The button idea would not affect any functionality, the button would only test the system, " test cycle". All other functions would remain the same.

The bolts didn't break, we found 3 on the road, luckily, I had no spares.

bottom line is:- there is no fail safe on this attachment. Spigot located wheels have extra security.
You could mount spigot type wheel with 2 studs stay on for a long time.
Mounting a wheel without, would possibly travel 100 metres.

I don't know how many car wheels part company.
When was the last time you torqued a car wheel bolt, certainly not twice on every journey.

Positive nut locking would keep the bolts in the tapered seating.

The danger of wheels without spigot:-
No certainty on eccentric running.
As soon as as the bolts slacken off, the wheel becomes eccentric. As this progresses the bolts soon undo , nearside only.

I've seen people argue that, VW beetles and Citreon 2 CVS had no spigot. Not a good reason to adopt a poor 60 year old design.
We have airbags,abs,traction control, radial tyres,split breaking systems,seat belts.crumple zones.


No, I don't have calibrated torque wrenches.
I have 2 with different ranges but 130nm.
Is available on both.
These both agree. Maybe they are both wrong?

I would just like to add a note that the only purpose of a spigot is to make things easier to centre the wheel on assembly to the axle. It has no load carrying ability because, for manufacturing tolerance reasons, it must have clearance to the wheel when the bolts are tightened up,

Just found this information, it might clear up any doubts. Just assume we started from a situation with loose bolts.
This is what Ronal Wheels USA had to say about hub centricity...

"Hubcentric" is another term that is often not mentioned or is misunderstood. A hubcentric wheel is a wheel designed with a centerbore opening to match the exact diameter of the hub of a specific vehicle. The importance is that the weight bearing of the wheel, in reference to the vehicle, is accomplished by the hub and centerbore mating to an exact fit. The lug nuts/bolts' only purpose is to affix the wheel to the mounting surface, not to bear the weight of the vehicle. Often wheels that are not hubcentric create driveability problems--shimmy, vibration, and erratic tracking. Many quality manufacturers design their wheels to be versatile by providing hubcentric centering rings that snap into place inside the wheel, to make the wheel hubcentric. This is an important safety issue--hubcentricity is highly recommended.

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[Lutz]

Just found this information, it might clear up any doubts. Just assume we started from a situation with loose bolts.
This is what Ronal Wheels USA had to say about hub centricity...

"Hubcentric" is another term that is often not mentioned or is misunderstood. A hubcentric wheel is a wheel designed with a centerbore opening to match the exact diameter of the hub of a specific vehicle. The importance is that the weight bearing of the wheel, in reference to the vehicle, is accomplished by the hub and centerbore mating to an exact fit. The lug nuts/bolts' only purpose is to affix the wheel to the mounting surface, not to bear the weight of the vehicle. Often wheels that are not hubcentric create driveability problems--shimmy, vibration, and erratic tracking. Many quality manufacturers design their wheels to be versatile by providing hubcentric centering rings that snap into place inside the wheel, to make the wheel hubcentric. This is an important safety issue--hubcentricity is highly recommended.

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• 
  

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If the above were true there wouldn't be any point in having conical bolts. Either the wheel is centred by a spigot or by conical bolts. Manufacturing tolerances dictate that it can't be both.

 

[JTQ]

This is what Ronal Wheels USA had to say about hub centricity...

I would not believe all you read on the internet!

As already explained, even if not understood, we can't get the interference fit needed to deal with our vehicle wheels radial loading, and still be able to mount and more importantly get the wheels off stood by the road side.
If the fit allows you to mount and demount the wheel, it also allows the load to move the wheel relative to the hub. Assuming here the bolts are not working as they should, clamp the wheel to the hub.

Add to that, making matching hubs and wheels, across all similar vehicles, so they are not unique to each other will be very expensive, along with making the fit surfaces very delicate to any abuse.

Not looking like what car makers, car buyers or car users are seeking?

 

[Sam Vimes]

The smart alternator can't lower the voltage below battery voltage - ATC is designed to work even at that voltage otherwise you could never reset the memory which needs battery voltage for 24 hours.

While is true the alternator can't lower the voltage of the battery, the real issue is what is the voltage across the load. Whether the battery or alternator is supplying the power the load will not see the same voltage as the source due to the voltages drops along the wires and connectors. This can be exacerbated by incorrect wiring sizes, poor wiring distribution, too many connectors and poor quality connectors including corrosion.

Obviously more current a load needs the larger the voltage drop.

Properly designed power distribution systems will incorperate sense wires to measure the voltage at the load and then adjust the output of the source to overcome the difference. But then that's a step too far for caravan manufacturers I guess.