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JCloughie

Wheel Detachment!

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Sorry John, but increased area itself has zilch affect on the friction forces involved; it does once plastic deformation steps in. Seems odd but it is a common misunderstanding. There is a bit in this link re area.

 

http://www. dummies. com/how-to/content/how-surface-area-affects-the-force-of-friction. html

 

Bigger bolts can carry more force which is useful, but only if there is adequate elasticity to hold that force once any substrate "give" occurs.

But the last sentence seems to say differently.

 

"Note that this relationship breaks down when the surface area gets too small, since then the coefficient of friction increases because the object may begin to dig into the surface."

 

But then that might depend on the definition of 'small'

 

Not trying to be awkward, just an observation. Wouldn't the higher torque a larger diameter bolt would allow increase the friction? A bit like increasing the height to go back to the dummies example.

 

John

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As I recall, the first topic on wheel detachment on this forum was some years ago shortly after the introduction of the Pegasus.

 

In summary and from memory some of the detachments, which largely occurred on caravans with alloy wheels, were put down to the failure of some drivers to check the torque before each and every journey and also after 15 or 20 miles into the journey. Instructions went out to dealers to advise them to draw the attention of customers of this advice or requirement.

 

The advice was quite specific about using a torque wrench every time and not to rely on other methods of checking the tightness. This advice also lead to dealers who serviced caravans passing on the advice to customers. This advice had been in users manuals for some time before this but as wheel detachment was possibly a fairly rare event until then the advice was not often followed. It be than many of these incidents had not been reported due the lack of Social media until then.

 

About this time Lidl and Aldi, and quite by chance, were offering torque wrenches in some of their weekly special offers. I would hazard a guess that the majority of wrenches were bought by caravanners, some of whom are probably still following the advice. ;)

 

After carrying out various tests and studying the wheel detachment incidents the manufacturer seemed to conclude that the WSL wheel bolt was more appropriate for use with the alloy wheels supplied.

 

What I cannot understand is why alloy wheels were chosen for fitting to what is effectively a box trailer with fancy internal fittings?

 

It seems to me that as one of the probable causes of wheel detachment has been identified and a remedy produced there appears to have been a decline in reported wheel detachment incidents which would indicate that there is little justification in being proactive and engineering out as far as possible any other possible causes of wheel detachment.

 

From my understanding of the issue, as Anne Robinson would say "Driver you are the weakest link"

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But the last sentence seems to say differently.

 

"Note that this relationship breaks down when the surface area gets too small, since then the coefficient of friction increases because the object may begin to dig into the surface."

 

But then that might depend on the definition of 'small'

 

Not trying to be awkward, just an observation. Wouldn't the higher torque a larger diameter bolt would allow increase the friction? A bit like increasing the height to go back to the dummies example.

 

John

 

As I said only when the surfaces finally give way to plastic deformation, ie one bit digs into the other, so loads gone beyond compressive limits which we certainly hope is not happening here.

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In the case of bolt threads, the more threads that are engaged, the more frictional resistance there is to them working loose. Theoretically, and the caravan manufacturers obviously believe this,

correctly torqued wheel bolts will not (should not?) loosen during travelling.

Some causes for detachment can be due to several, and cumulative, reasons.

(a)The service engineer does not apply the correct torque, and the owner does not recheck.

(b)The owner does not check sufficiently regularly that all is OK.

©The torque wrench being used is inferior to the job it is supposed to do.

(d)The torque wrench was of good quality when new, but is now old an well past its 'sell by' date.

(f)Owners applying grease or oil to bolt threads and/or cone faces. A definite no-no.

(g)An absolutely reliable torque wrench, correctly used by the owner over more than adequate time

periods.

 

The last observation (g) is the one that gives us the most concern, because this is where the

inexplicable occurs. Also, some reduction in the occurrences of wheel detachment may be

attributable to an increasing number of owners paying greater and more frequent attention to the

checking of their wheel bolts. Even so, these owners, when the worst happens, are at a loss to

understand why they have suffered this detachment problem, in spite of their extreme care. And, at

present, nobody in the industry seems to be sympathetic or share their concern.

 

One aspect perhaps not yet considered is the coefficient of expansion of the wheel bolt. Braking

generates heat, which can be dissipated through the axle assembly and to the bolts. Any significant

increase in the length of the bolt between the threads and the underside of its cone MIGHT be

contributory to loss of applied torque, and thereby more susceptible to loosening by road vibration.

 

My own feelings are that the industry should jointly co-operate to get some body such as MIRA

interested in carrying out experimental bench tests in an effort to discover just why caravan alloy

wheels are prone to this detachment phenomenon.

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Just wondering . . it seems the problem was with the alloy wheels (not steel) on those Baileys.

 

Different patterns are used on different vans . . could it have been the wheel itself that caused the problem . . different manufacturer maybe . .

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As discussed much earlier in this topic, the reason I know about the different bolt size is that a French motorhome dealer was going to replace my damaged hub. He ordered a new one using a number stamped on the old hub. When he tried to fit it he found it was exactly the right size but the hole size and spacing were both larger.

 

My point is, given that the physics remain the same, how can 12 mm be OK for 1 but others specify 14 mm.

 

 

 

 

As you discovered Al-Ko will supply the same brake drum with different bolt diameter and PCD to the customer's requirements.

It is extremely unlikely that a bolt size unsuitable for the type of trailer to which a particular drum could be fitted would be designed by Al-Ko

 

Some French cars have 14 mm wheel bolts perhaps the French caravan market caters for a common size?

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As you discovered Al-Ko will supply the same brake drum with different bolt diameter and PCD to the customer's requirements.

It is extremely unlikely that a bolt size unsuitable for the type of trailer to which a particular drum could be fitted would be designed by Al-Ko

 

Some French cars have 14 mm wheel bolts perhaps the French caravan market caters for a common size?

The design of the PCD and bolt size is a joint decision between Alko and the manufacturer. Alko began to tell me this until the chap realised that I was victim and he very quickly shut up.

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In the case of bolt threads, the more threads that are engaged, the more frictional resistance there is to them working loose.

 

 

Not true; Unless, of course for centuries physicists and engineers have got the theory of friction all wrong and the classic formula, friction force (static) = µ x Normal force, actually needs an "area" term introduced. ;)

 

Some causes for detachment can be due to several, and cumulative, reasons.

(a)The service engineer does not apply the correct torque, and the owner does not recheck.

(b)The owner does not check sufficiently regularly that all is OK.

©The torque wrench being used is inferior to the job it is supposed to do.

(d)The torque wrench was of good quality when new, but is now old an well past its 'sell by' date.

(f)Owners applying grease or oil to bolt threads and/or cone faces. A definite no-no.

(g)An absolutely reliable torque wrench, correctly used by the owner over more than adequate time

periods.

 

 

I suggest we have left out a fundamental, multi faceted cause. The stability of the clamped components. ie what on the surfaces might give under load? This includes paints, metallic plating, dirt, grease, corrosion products on the mating surfaces, importantly including in the threads. Plus the quality of the machining on the surfaces, the mating and the threads themselves. Any "give", that is, settling here depletes the stored energy in the strain of the bolt, and of all the loaded parts. That is why bolts with plenty of elasticity do a much better job, as WSL know so well by increasing their strain energy by over three times that of the standard bolt.

 

On point (f) it is quite right, we must definitely not use any additional lubricant above, say the zinc plating used on the threads; to do so will lead to over tensioning the bolts, as the designer chappie here is quoting a "dry torque-up value". Where we need more precise, more repeatability in bolt loading we do actually lubricate the threads, but the torque up figure specifically takes this into account.

 

IMO the wheel failures in cases where all precautions have known to have been taken, rest, at surface "give" in some parts of the mated surfaces. I have done plenty of testing of bolted assemblies so know what massive impact it has. [not automotive]

With short working length bolts, as soon as that occurs the frictional clamping can't take the loads, including shock loads, and let the main clamped surfaces move, quickly all going wrong until the bolts even start to turn as things giggle about. Hence my view the wheel bolt markers are as much use as a chocolate fire guard, and nice stretchy bolts give a great deal more reserves.

Edited by JTQ
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I am very sorry to hear of your ordeal Cloughie.

Wheel detachment was a problem on HGV's for quite a while, mostly on the nearside. It was thought to be caused by extra stress because of road camber. With the introduction of metric threads this problem became a nightmare.

IMHO your problem is caused by "clever lauddies"---new designs of hubs and bolts etc.

For many years, both on car and commercial wheels, we assembled with a very thin coating of copper grease and tightened (without torque wrench) as tight as a Ducks A--e.

Over hundreds of wheel fittings we only had one HGV trailer which kept losing the N/S rearmost wheels. We tried everything with this vehicle but never resolved the problem---reckoned it was an axle fault.

The higher tech you get, the more ( difficult) problems it throws up.

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problem is, there is no significant design difference between car wheel bolts and caravan wheel

bolts, hence my own theory explaining other possible reasons. I may be right and I may be wrong; at

this time nothing has been proven or disproven as to the real cause. To date, it has not even been

proven, despite service engineers/owners' claims to have tightened the bolts correctly, that the

problem is still not really a case of human error by the person doing the tightening.

Two things that are not advisable, blondchaser:

1. Never put copper grease or any other kind of lubricant on the threads or the mating cones of

wheel bolts - this definitely reduces frictional resistance to loosening, and the warning is cast

in stone in automotive practices.

2. In not using a torque wrench there is no knowledge by the person doing the tightening that the

bolts are either not tight enough, or have had enough torque applied so as to be weakened by

exceeding their ultimate tensile strength.

 

Gone are the days when automotive nuts and bolts were deliberately made to dimensions far in excess

of their design needs. Today they are designed to strict parameters that, whist not being

excessively heavy or bulky, still meet the requirements of critical safety factors. That is why,

throughout the whole of the engineering industry, specific torque settings are applied to every

fastener employed in a safety critical situation. Thus, the use of a torque wrench, reliably

accurate, and set to the correct specified torque load, is the only way to do the job properly.

To deny this would be to say that every world wide production plant and service department have

got it wrong.

assembly procedures (without lubricants if is says not to use them)

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1. Never put copper grease or any other kind of lubricant on the threads or the mating cones of

wheel bolts - this definitely reduces frictional resistance to loosening, and the warning is cast

in stone in automotive practices.

 

 

Another near vital reason for not using a lubricant in the threads themselves [where the quoted torque-up is not stated as lubricated], is that the reduced thread friction can easily increase the achieved bolt tension by 20%. More if comparing to used bolts where the lubricity of the plating has been lost. This also accounts for lack of adequate tension being generated where threads are rusty and a greater amount of the applied torque is lost in overcoming thread friction.

 

 

I am though well aware that the practice is widespread outside controlled industries like aviation, so I expect here the designers use over rated fixings to counter the inevitable, but often well intended abuse vehicles receive out in the field.

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Gone are the days when automotive nuts and bolts were deliberately made to dimensions far in excess

of their design needs. Today they are designed to strict parameters that, whist not being

excessively heavy or bulky, still meet the requirements of critical safety factors.

 

 

Though I agree with your logic and comments, I feel they got it wrong in this case.

 

 

------------------------------

 

I think I have said it before and I am not using this as an excuse for my wheel detachment.

 

I bought my Valencia at 5 month old so did not have the benefit of a hand over. So I can not say that the original owner was instructed in the timing and use of a torque wrench.

 

The instructions have a small message saying something like check the torque of all bolts before each journey. No instruction or advice.

 

A torque wrench was not supplied with the van, or as an optional extra. Yet the customer is suppose to check before each trip.

 

On collection after each service I was never asked to watch or sign that they wheels had been properly checked.

 

Seems to me that the industry pays little attention to the safety of their customers. Perhaps it is not a good selling point to have to instruct customers in the use of a torque wrench, may put people off.

 

John

Edited by JCloughie
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The design of the PCD and bolt size is a joint decision between Alko and the manufacturer. Alko began to tell me this until the chap realised that I was victim and he very quickly shut up.

 

It is difficult to understand why you keep returning to this particular matter. The dealer concerned ordered a brake drum to the wrong specification and it seems that having discovered that some (French) caravans use an M14 bolt you feel your caravan with M12 bolts has a design fault. Or is that a misunderstanding of the situation?

If that really is the case then almost all the European caravan industry is in the same position as not only Al-Ko but BPW and Knott/Avonride also use M12 bolts

 

Al-Ko user handbook states. .........

 

ROAD WHEELS

In most instances the road wheels and tyres are supplied by the Caravan Manufacturer.
IMPORTANT NOTE
Standard AL-KO caravan chassis use M12 bolts.
These must always only be tightened to the correct torque setting as recommended by the vehicle manufacturer.
Always use a calibrated torque wrench. ..... .....
It is as dangerous to overtighten wheel bolts as it is to not tighten them sufficiently.
IMPORTANT NOTE
The torque settings should be re-checked after 50 km.
If other wheel bolts are used please ensure the torque settings are
as follows:
M10 - 49 Nm (36 ft. lb)
M14 - 135 Nm (99. 5 ft. lb)

M16 - 210 Nm (155 ft. lb)

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It is difficult to understand why you keep returning to this particular matter. The dealer concerned ordered a brake drum to the wrong specification and it seems that having discovered that some (French) caravans use an M14 bolt you feel your caravan with M12 bolts has a design fault. Or is that a misunderstanding of the situation?

If that really is the case then almost all the European caravan industry is in the same position as not only Al-Ko but BPW and Knott/Avonride also use M12 bolts

 

Al-Ko user handbook states. .........

 

ROAD WHEELS

In most instances the road wheels and tyres are supplied by the Caravan Manufacturer.
IMPORTANT NOTE
Standard AL-KO caravan chassis use M12 bolts.
These must always only be tightened to the correct torque setting as recommended by the vehicle manufacturer.
Always use a calibrated torque wrench. ..... .....
It is as dangerous to overtighten wheel bolts as it is to not tighten them sufficiently.
IMPORTANT NOTE
The torque settings should be re-checked after 50 km.
If other wheel bolts are used please ensure the torque settings are
as follows:
M10 - 49 Nm (36 ft. lb)
M14 - 135 Nm (99. 5 ft. lb)

M16 - 210 Nm (155 ft. lb)

 

 

 

I am only returning as it pops up naturally in reply to other postings, in this case in reply to 'The 2 Tops' in 224, not everybody would have read everything. Yes, you are right, I am suggesting a possible design fault. I am also questioning the sense, or lack of (in my opinion) of reinventing the wheel. If one standard exists for a 1600 chassis, why try to dumb it down at the possible expense of safety.

 

One thing that is clear, the cause of wheel detachment has been discussed on this forum at great length. with the same points raised very often. but it seems that we amateurs or the industry are no closer except, possibly for the WSL.

 

Some odd things about your reference.

 

Standard Alko Chassis uses M12. ....... but that is only true for Alko UK

 

See Manufacturer for Torque settings for M12, but M14 and M16 are given M14 and M16 are not consistent. M14=49 Nm, (seems exceptionally low)

 

We do not know how widespread M14 are on the continent, you said 'some French Caravans'. But the French fitter was adamant that M14 is the norm in France, have we got it wrong?

 

Wheel detachment may be due to many things or a combination, but if its being discussed lets make sure that relevant information is included in the pot. I personally think that the difference between M12 and M14 is very significant and should not be dismissed just because Caravan manufacturers deem it suitable and bury their heads in the sand when there is a problem.

 

I am not sure what you are saying, don't you think the difference between the 2 sizes is significant/relevant.

 

 

John

Edited by JCloughie

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Post #236 - JTQ, Regarding such things as rusty bolts, etc. , I think we have to work on the principle that the wheel bolts and hub threads are in a satisfactory condition and without significant wear that could affect performance, otherwise a whole new can of worms will be opened. We have to assume that the wheel detachment problem relates to caravans with unworn to new condition of the components, otherwise excessive wear/damaged components would come into the equation.

 

Designers do not "use overrated fixings to counter the inevitable" - in fact I would say that caravan chassis manufacturers pretty much follow automotive industry practices where their running gear is of similar design.

In exactly the same way that motor manufacturers stipulate wheel bolt torque values for cars, caravan chassis manufacturers use the same criteria. They do not use overrated fittings and then apply guesswork.

In fact, overrated fittings would not resolve the problem of wheel detachment if the experiences described by unfortunate

owners are not due to human error.

 

Post #237 - John, at one time torque setting figures were not passed on to the user of motorcars or caravans, although I cannot

explain why that was. However, it is now standard practice for the handbooks of both to carry the necessary information - our

2012 caravan has the torque wrench settings given on the same plate that carries the MTPLM and MRO loadings, and covers

both the alloy wheels and the different torque for the steel spare wheel.

 

Like caravans, cars also do not come with a supplied torque wrench, but do we not still equip ourselves with such a tool and use it for our cars? Among other necessary equipment I carry a 24" breaker bar for loosening off car and/or caravan wheel bolts,

and a torque wrench for refitting them. The SUPPLIED wheel wrenches for both car and caravan are, quite frankly, useless.

Even the most proficient engineer would be using total guesswork in using them.

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Like caravans, cars also do not come with a supplied torque wrench, but do we not still equip ourselves with such a tool and use it for our cars? Among other necessary equipment I carry a 24" breaker bar for loosening off car and/or caravan wheel bolts,

and a torque wrench for refitting them. The SUPPLIED wheel wrenches for both car and caravan are, quite frankly, useless.

Even the most proficient engineer would be using total guesswork in using them.

I can remember when tyre fitters did not use torque wrenches, then, when air wrenches became popular they used them to put both on and off. As a consequence I once had a sheered bolt and another time put my shoulder out trying to remove a wheel in heavy rain outside Fords Halewood.

 

After this I insisted that they used a torque wrench and got some odd remarks, it was also clear that they had no idea what torque to set. (Around 1978).

 

We have moved on, however far from people equiping themselves with a torque wrench, the vast majority of the people I know do not have one, most will not know what one is and less how to use one. Most people do not touch their own car wheels and rely on the yearly service.

 

To a lesser extent I believe caravaners are the same.

 

I feel the need to supply a wrench with a car is not necessary, but, if there is a genuine problem with modern caravans, perhaps one should be. But that would mean that manufacturers would need to admit that there is a problem.

 

John

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Peeps, having glanced over this thread, I mentioned it to the wife, them being more simple than us men, she simply asked me 'does this wheel falling off business affect just Alutech vans, or do we (think more me) need to invest in a torque wrench and add it to the front locker, and regularly check tightness? I had no answer to her. ...............

so, as we have a nice 2010 van, and I do prefer the look of the thing with both wheels on. ........should I be popping to halfords to pick one up?

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Peeps, having glanced over this thread, I mentioned it to the wife, them being more simple than us men, she simply asked me 'does this wheel falling off business affect just Alutech vans, or do we (think more me) need to invest in a torque wrench and add it to the front locker, and regularly check tightness? I had no answer to her. ...............

so, as we have a nice 2010 van, and I do prefer the look of the thing with both wheels on. ........should I be popping to halfords to pick one up?

Consider one of these, good price, lighter to carry.

 

https://www. machinemart. co. uk/shop/product/details/040215238?da=1&TC=SRC-torque

 

 

John

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John, I am surprised that you feel that a torque wrench is not necessary for cars (if I understood

you correctly in your last paragraph of post #241). If you have to change a wheel then you do

need to be sure that the fresh wheel has its bolts tightened to the correct torque. Both my car and

my caravan wheel bolts, when removed for any reason, are always tightened by using the torque wrench when refitted. Also, when both vehicles have been for their annual service, I recheck the wheel

bolts with my own torque wrench. It doesn't concern me if a service engineer is a bit miffed because he may feel a degree of mistrust - mistakes can happen and it is myself who carries the

responsibility if the worst happens whilst on the road.

 

The Machine Mart tool in your link looks interesting. I don't know how well it would perform against a more expensive tool like my Norbar wrench - you usually get what you pay for - and I still feel

that a periodic calibration check is required to ensure future accuracy.

 

Air-wrenches - horrible things! They MIGHT be OK for releasing the bolts (still prefer not), but to

use them to refit the bolts is a definite no-no. I believe a lot of the better garages and tyre

fitting depots have now discontinued using them.

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John, I am surprised that you feel that a torque wrench is not necessary for cars (if I understoodyou correctly in your last paragraph of post #241). If you have to change a wheel then you doneed to be sure that the fresh wheel has its bolts tightened to the correct torque. Both my car andmy caravan wheel bolts, when removed for any reason, are always tightened by using the torque wrench when refitted. Also, when both vehicles have been for their annual service, I recheck the wheelbolts with my own torque wrench. It doesn't concern me if a service engineer is a bit miffed because he may feel a degree of mistrust - mistakes can happen and it is myself who carries theresponsibility if the worst happens whilst on the road. The Machine Mart tool in your link looks interesting. I don't know how well it would perform against a more expensive tool like my Norbar wrench - you usually get what you pay for - and I still feelthat a periodic calibration check is required to ensure future accuracy. Air-wrenches - horrible things! They MIGHT be OK for releasing the bolts (still prefer not), but touse them to refit the bolts is a definite no-no. I believe a lot of the better garages and tyrefitting depots have now discontinued using them.

Sorry if I worded my thoughts badly, I meant I do not see a necessity to supply a torque wrench with a new car. Clearly they should be used but most people only get theirs torqued after a service, or wheel removal.

 

If, as with Bailey, a torque check is needed before each trip it becomes standards equipment, that why I was suggesting that it should be supplied.

 

Re digital wrench.

 

The blurb says it is very accurate (can't remember the details). Also it can be used to check conventional wrenches.

 

John

Edited by JCloughie
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Despite knowing what I “ought” to do, I don’t actually carry a torque wrench everywhere. It resides at home and is used occasionally there, where the cars and van are kept.

 

My van came from Germany with a telescopic brace for wheel changing; this also conveniently sets my Powrtouch mover. So I use that for any on route checks I chose to make, rather than carry yet more clobber.

 

Yes, I do rely on my own judgement on whether the bolts are snug enough; been involved long enough to be confident of not being a mile out. This being endorsed by my measured rechecks made at home.

Apart from failings found after a few non DIY services or tyre changes, I can’t remember another single occasion in 55 years of motoring that I ever found a bolt requiring attention.

 

What I do though is regularly check things, both properly and in my somewhat less refined way.

More often the latter is done when with wrench already in hand I am standing by one wheel, having set the mover.

My bolts are accessible, no inhibiting pointless plastic indicators are fitted, The security bolt's key also lives in the wrench bag so is readily picked up when going from car boot to set the van mover.

 

Easy enough done; caravanning to us needs to be as low a hassle recreation as practical.

 

On torque wrenches I like the deflected bar type, they don’t need resetting, after being made, as Young’s modulus does not drift. If it still shows zero when picked up it will be as good as the day it was made; provided it was calibrated then. We made and calibrated them with dead weights as part of our tool making apprenticeship, and over the years made others for high precision jobs.

 

John could use the dead weight method to do a spot check on his digital device, ideally at his required torque. Basically, clamp drive end in vice, and hang a known weight at a known distance from the drive. We have used water knowing a litre weighs a kg, and used a steel tube to extend the lever if needed. [For the purists it is easy to compensate for the tube's influence ;) ]

Edited by JTQ
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My wrench is calibrated every 6 months at work. .. A decent snap on half inch job, I will be checking my wheel bolts before each trip from now on I think.

Edited by Din

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I keep reading that wheel bolt torque should be checked after about 50 miles or so of a journey.

 

I also seem to remember reading ( probably here on CT ) that hot/warm wheel bolts should be left to go cold before checking as to do otherwise would result in incorrect readings.

 

I can imagine SWMBO's reaction ( who is not renouned for her patience ) at having to wait a couple of hours for the bolts to cool mid journey.

 

Ian

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Just checked, Bailey handbook says, before hitching up always check the torque. (Paraphrased)

 

John

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I keep reading that wheel bolt torque should be checked after about 50 miles or so of a journey.

 

I also seem to remember reading ( probably here on CT ) that hot/warm wheel bolts should be left to go cold before checking as to do otherwise would result in incorrect readings.

 

I can imagine SWMBO's reaction ( who is not renouned for her patience ) at having to wait a couple of hours for the bolts to cool mid journey.

 

Ian

 

The precision the designer can quote for torquing up these bolts, to cover brand new bolts, those burnished by being previously done up, and those with a trace of surface corrosion, is so wide it makes a complete nonsense of the stance some would want us to take. Check them 20 to 30 miles after they are disturbed for whatever reason, the end of that trip again, then every few months.

 

You will greatly improve your chances of them remaining sound, as I have laboured before, by using bolting that stores more energy. They are not "necessary", I don't use them, but have designed them into arduous duty bolted joints. As I said they will greatly increase the likelihood of remaining tight, during that critical early post disturbance period. After that IMO the supplied bolting has adequate reserves, but periodic checking is important, though most unlikely to prove necessary.

 

Buy her a set for Valetine's Day to show you really love her.

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